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DrNGPInstitute of TechnologyCoimbatore - 48
UNIT I - INTRODUCTION TO AVIONICS
1 What is Avionics State the role and importance of avionics
Avionics is a word derived from the combination of aviation and electronics The term avionic system or avionic subsystem is to mean any system in the aircraft which is dependent on electronics for its operation The avionics industry plays a vital role in multi-billion dollar industry worldwide and the avionics equipments accounts for around 30 of total cost of aircraft The avionic systems are essential to enable the flight crew carry out the aircraft mission safely and efficiently
2 Illustrate the overall picture with the roles and functions of Core Avionic Systems
3 Enumerate the systems which interface directly with the pilotThe various systems which interface directly with the pilot are displays communications data entry and control
and flight control The display system provide the visual interface between the pilot and the aircraft systems The data entry and control systems are essential for crew to interact with the avionic systems The flight control system comprises of auto stabilization and FBW flight control systems These systems form the first layer in avionics tasks and functions
4 Write Short notes on aircraft state sensor systemsAircraft state sensor systems is the second layer in avionics specific tasks and functions The Air Data Systems
and Inertial sensor systems are the classification of aircraft state sensor systems The Air data systems provide accurate information on their data quantities which is essential for control and navigation of the aircraft The inertial sensor systems provide information for the pilot to execute a manoeuvre or flying in conditions of poor visibility
5 What is meant by Dead Reckoning Navigation System List the types of DR Navigation systemsDead Reckoning Navigation Systems derive the vehiclersquos present position by estimating the distance traveled
from a known position from knowledge of the speed and direction of motion of vehicle The main types of DR navigation systems used in aircraft are
1 Inertial Navigation Systems2 DopplerHeading Reference Systems
DrNGPInstitute of TechnologyCoimbatore - 48
3 Air DataHeading Reference Systems
6 What is the function of Outside World Sensor Systems The outside world sensor systems comprise both radar and infrared sensor which enable all weather and night
time operation and transform the operational capability of the aircraft (or helicopter) The Radar Systems installed in civil airliners and many general aviation aircraft provide weather warning The Infrared Sensor Systems can be used to provide a video picture of the thermal image scene of the outside world either using a fixed FLIR sensor or a gimbaled IR imaging sensor
7 Interpret the tasks carried out by flight Management System The tasks carried out by the FMS include1 Flight Planning2 Navigation Management3 Engine Control to maintain the planned speed or Mach number4 Control of the aircraft flight path to follow the optimized planned route5 Control of the vertical flight profile6 Flight envelope Monitoring7 Minimizing fuel consumption
8 How weight is overcome by lift to hold the plane in the airLift is the force that directly opposes the weight of an airplane and holds the airplane in the air Lift is generated
by every part of the airplane but most of the lift on a normal airliner is generated by the wings
9 With neat sketch depict the forces acting on the airplane
10 What is the inference obtained from the forces acting on an aircraftThe motion of the airplane through the air depends on the relative strength and direction of the forces like thrust
drag weight and lift If the forces are balanced the aircraft cruises at constant velocity If the forces are unbalanced the aircraft accelerates in the direction of the largest force
11 Contrast the Horizontal Stabilizer and Vertical Stabilizer To control and maneuver the aircraft smaller wings are located at the tail of the plane The tail usually has a fixed horizontal piece called the horizontal stabilizer and a fixed vertical piece called the vertical stabilizer The vertical stabilizer keeps the nose of the plane from swinging from side to side which is called yaw The horizontal stabilizer prevents an up-and-down motion of the nose which is called pitch
12 What are the characteristics of Rudder
DrNGPInstitute of TechnologyCoimbatore - 48
The hinged part of the vertical stabilizer is called the rudder it is used to deflect the tail to the left and right as viewed from the front of the fuselage The rudder input insures that the aircraft is properly aligned to the curved flight path during the maneuver The rudder works by changing the effective shape of the airfoil of the vertical stabilizer
13 List the steps in Pitch processA pitch motion is an up or down movement of the nose of the aircraftThe pitching motion is being caused by the
deflection of the elevator of this aircraft The elevator is a hinged section at the rear of the horizontal stabilizerThe pitch axis is perpendicular to the aircraft centerline and lies in the plane of the wings
14 What is the need for two different speeds in ARINC 429ARINC 429 specifies two speeds for data transmission Low speed operation is stated at 125 kHz with an actual
allowable range of 12 to 145 kHz High speed operation is 100 kHz plusmn 1 allowed These two data rates cannot be used on the same transmission bus
15 Justify the need for communication system in a civil transport aircraft Aircraft need to communicate and find out where they are and where they are going Most civil aircraft have a
VHF radio They communicate with the air traffic control in the 118 - 136 MHz band Additionally they might be equipped with HF radio this has greater range and typically used over oceans Commercial aircrafts use VHF but also have Satellite communications Military use VHF UHF and HF
16 Draw the roll axis and roll motion in an aircraft
17 Compare the different avionic systems and bring out their merits and demerits
Centralized Architecture Simple design Software can be written easily Computers are located in readily accessible bay
Disadvantages Requirement of long data buses Low flexibility in software Increased vulnerability to change Different conversion techniques are needed at the central computer
Federated Architecture Increased Information Fusion Higher levels and complexity of software Standardization for maintenance simplification Lower costs Backward and growth capability while making use of emerging technology ndash VHSIC Voice
DrNGPInstitute of TechnologyCoimbatore - 48
Recognition synthesis and Artificial Intelligence Provides capability for rapid flow of data in through and from the system as well as between and
within the system Higher levels of avionics integration and resource sharing of sensor and computational capabilities Pilot plays the role of a WEAPON SYSTEM MANAGER as opposed to subsystem
operatorinformation integrator Able to sustain operations with minimal support fly successful mission day and night in any type of
weather Face a numerically and technologically advanced enemy aircraft and defensive systems
Advantages Component reliability gains Use of redundancy and resource sharing Application of fault tolerance Reduction of maintenance test and repair time Increasing crew station automation Enhancing stealth operation Wide use of common modules (HW amp SW)) Ability to perform in-aircraft test and maintenance of avionics Use of VHSIC technology and Capability to operate over extended periods of time at austere
deployed locations and be maintainable without the Avionics Intermediate Shop
18 What do you mean by Engine control and managementEngine control and management monitors the engines condition automatically controls the flow of fuel and
respond to throttle command Control system It ensures the engine limits in terms of temperatures engine speeds and accelerations and the engines respond in an optimum manner to the throttle command
19 What do you mean by House keeping management The term house keeping management has been used to cover the automation of the background tasks which are essential for the aircrafts safe and efficient operation Such tasks include
Fuel management Electrical power supply system management Cabincockpit pressurization systems Environmental control system Warning systems Maintenance and monitoring systems
20 State the importance of Radar systemsInstalled in all civil airliners amp in many general aviation aircraft
bull To detect water droplets and provide warning of storms cloud turbulence and severe precipitation-aircraft can alter course and avoid such turbulent conditionsbull It should be noted that in severe turbulence the violence of the vertical gusts can subject the aircraft structure to very high loads and stresses These radars can also generally operate in ground mapping and terrain avoidance modes bull In the airborne interception mode the radar must be able to detect aircraft upto 100 miles away and track while scanning and keeping tabs on several aircraft simultaneously bull The radar must also have a look down capability and be able to track low flying aircraft below it
21 Write short notes on MIL STD 1553 MIL-STD-1553 is a military standard published by the United States Department of Defense that defines the
mechanical electrical and functional characteristics of a serial data bus It was originally designed as an avionic data bus for use with military avionics but has also become commonly used in spacecraft on-board data handling (OBDH) subsystems both military and civil It features multiple (commonly dual) redundant balanced line physical layers a (differential) network interface time division multiplexing half-duplex commandresponse protocol and can handle up to 31 remote terminals (devices) A version of MIL-STD-1553 using optical cabling in place of electrical is known as MIL-STD-1773
DrNGPInstitute of TechnologyCoimbatore - 48
22 Categorize the key elements of MIL STD 1553Some of the key MIL-STD-1553B elements are the bus controller the embedded remote terminal (a sensor or
subsystem that provides its own internal 1553 interface) the stand-alone remote terminal bus monitor and two other devices that are part of the 1553 integration the twisted shielded pair wire data bus and the isolation couplers that are optional
23 What is the purpose of Data Bus CouplerThe data bus coupler unit that isolates the main bus from the terminals MIL-STD-1553B allows two types of
data bus interface techniques direct coupling and transformer coupling Subsystems and 1553 bus elements are interfaced to the main data bus by interconnection buses (called ldquostubsrdquo) These stubs are either connected directly to the main bus or interfaced via data bus couplers The data bus couplers contain two isolation resistors (one per wire) and an isolation transformer (with a ratio of 1 to the square root of 2) The purpose of the data bus couplers is to prevent a short on a single stub from shorting the main data bus
24 Which types of coupling may be used in the ARINC 629 bus systemARINC 629 uses both current and voltage coupling modes of operation In current mode coupling the couplers
used are inductive in nature The current mode is advantageous than voltage mode as the bus wire does not have to be broken to insert the RT and if a unit is removed the bus does not have to be reconnected
25 Justify the need for label in an ARNIC 429 systemTransmission from the source LRU is comprised of 32 bit words containing a 24 bit data portion containing the
actual information and an 8 bit label describing the data itselfThe only two fields definitively required are the Label and the Parity bit leaving up to 23 bits available for higher resolution data representation Many non-standard word formats have been adopted by various manufacturers of avionics equipment Even with the variations included all ARINC data is transmitted in 32 bit words Any unused bits are padded with zeros
26 Illustrate ARINC 629 Bus system with its components
27 Infer and interpret the bit format of ARNIC 429
DrNGPInstitute of TechnologyCoimbatore - 48
28 What are the major drivers for avionics systems in a typical civil transport aircraftThe major drivers for avionics systems in a typical civil transport aircraft are Fly by Wire Flight Controls Full
Flight Regime 4 D Flight Management Full Glass Cockpits FANS capability to operate in a new air traffic management environment Passenger entertainment systems On board central Maintenance computers and electronic Documentation
29 Explain Cockpit A cockpit or flight deck is the area usually near the front of an aircraft from which a pilot controls the aircraft
Most modern cockpits are enclosed except on some small aircraft Most Airbus cockpits are glass cockpits featuring fly-by-wire technology The cockpit of an aircraft contains flight instruments on an instrument panel and the controls that enable the pilot to fly the aircraft In most airliners a door separates the cockpit from the aircraft cabin
30 What is the significance of PFDThe primary flight display is usually located in a prominent position either centrally or on either side of the
cockpit It will in most cases include a digitized presentation of the attitude indicator air speed and altitude indicators (usually as a tape display) and the vertical speed indicator It will in many cases include some form of heading indicator and ILSVOR deviation indicators In many cases an indicator of the engaged and armed auto flight system modes will be present along with some form of indication of the selected values for altitude speed vertical speed and heading It may be pilot selectable to swap with the ND
DrNGPInstitute of TechnologyCoimbatore - 48
UNIT II -
1 What is navigationNavigation is the determination of the position and velocity of the mass center of a moving vehicle The three components of position and the three components of velocity make up a six-component state vector that fully describes the translational motion of the vehicle because the differential equations of motion are of second order
2 What is Radio Navigation
Radio navigation or radio navigation is the application of radio frequencies to determine a position on the Earth Like radiolocation it is a type of radio determination The basic principles are measurements fromto electric beacons especially
directions eg by bearing radio phases or interferometry distances eg ranging by measurement of travel times partly also velocity eg by means of radio Doppler shift
3 What are the characteristics of Automation Detection FinderADF is the oldest radio navigation system still in use ADF uses Non-Directional Beacons (NDBs) that are
simply AM-radio transmitters operating in the Low and Middle Frequency (LMF) Band from 190 to 535 kHz These frequencies are below the standard broadcast band All ADFs can also home in on AM broadcast stations Pilots can listen to the radio and navigate also The ADF indicator has a compass rose and an indicating needle The needle automatically points to the station
4 State the functionality of DMEIn the post-war era a general navigation system using transponder-based systems was deployed as the distance
measuring equipment (DME) system DME was identical to Gee-H in concept but used new electronics to automatically
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
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2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
3 Air DataHeading Reference Systems
6 What is the function of Outside World Sensor Systems The outside world sensor systems comprise both radar and infrared sensor which enable all weather and night
time operation and transform the operational capability of the aircraft (or helicopter) The Radar Systems installed in civil airliners and many general aviation aircraft provide weather warning The Infrared Sensor Systems can be used to provide a video picture of the thermal image scene of the outside world either using a fixed FLIR sensor or a gimbaled IR imaging sensor
7 Interpret the tasks carried out by flight Management System The tasks carried out by the FMS include1 Flight Planning2 Navigation Management3 Engine Control to maintain the planned speed or Mach number4 Control of the aircraft flight path to follow the optimized planned route5 Control of the vertical flight profile6 Flight envelope Monitoring7 Minimizing fuel consumption
8 How weight is overcome by lift to hold the plane in the airLift is the force that directly opposes the weight of an airplane and holds the airplane in the air Lift is generated
by every part of the airplane but most of the lift on a normal airliner is generated by the wings
9 With neat sketch depict the forces acting on the airplane
10 What is the inference obtained from the forces acting on an aircraftThe motion of the airplane through the air depends on the relative strength and direction of the forces like thrust
drag weight and lift If the forces are balanced the aircraft cruises at constant velocity If the forces are unbalanced the aircraft accelerates in the direction of the largest force
11 Contrast the Horizontal Stabilizer and Vertical Stabilizer To control and maneuver the aircraft smaller wings are located at the tail of the plane The tail usually has a fixed horizontal piece called the horizontal stabilizer and a fixed vertical piece called the vertical stabilizer The vertical stabilizer keeps the nose of the plane from swinging from side to side which is called yaw The horizontal stabilizer prevents an up-and-down motion of the nose which is called pitch
12 What are the characteristics of Rudder
DrNGPInstitute of TechnologyCoimbatore - 48
The hinged part of the vertical stabilizer is called the rudder it is used to deflect the tail to the left and right as viewed from the front of the fuselage The rudder input insures that the aircraft is properly aligned to the curved flight path during the maneuver The rudder works by changing the effective shape of the airfoil of the vertical stabilizer
13 List the steps in Pitch processA pitch motion is an up or down movement of the nose of the aircraftThe pitching motion is being caused by the
deflection of the elevator of this aircraft The elevator is a hinged section at the rear of the horizontal stabilizerThe pitch axis is perpendicular to the aircraft centerline and lies in the plane of the wings
14 What is the need for two different speeds in ARINC 429ARINC 429 specifies two speeds for data transmission Low speed operation is stated at 125 kHz with an actual
allowable range of 12 to 145 kHz High speed operation is 100 kHz plusmn 1 allowed These two data rates cannot be used on the same transmission bus
15 Justify the need for communication system in a civil transport aircraft Aircraft need to communicate and find out where they are and where they are going Most civil aircraft have a
VHF radio They communicate with the air traffic control in the 118 - 136 MHz band Additionally they might be equipped with HF radio this has greater range and typically used over oceans Commercial aircrafts use VHF but also have Satellite communications Military use VHF UHF and HF
16 Draw the roll axis and roll motion in an aircraft
17 Compare the different avionic systems and bring out their merits and demerits
Centralized Architecture Simple design Software can be written easily Computers are located in readily accessible bay
Disadvantages Requirement of long data buses Low flexibility in software Increased vulnerability to change Different conversion techniques are needed at the central computer
Federated Architecture Increased Information Fusion Higher levels and complexity of software Standardization for maintenance simplification Lower costs Backward and growth capability while making use of emerging technology ndash VHSIC Voice
DrNGPInstitute of TechnologyCoimbatore - 48
Recognition synthesis and Artificial Intelligence Provides capability for rapid flow of data in through and from the system as well as between and
within the system Higher levels of avionics integration and resource sharing of sensor and computational capabilities Pilot plays the role of a WEAPON SYSTEM MANAGER as opposed to subsystem
operatorinformation integrator Able to sustain operations with minimal support fly successful mission day and night in any type of
weather Face a numerically and technologically advanced enemy aircraft and defensive systems
Advantages Component reliability gains Use of redundancy and resource sharing Application of fault tolerance Reduction of maintenance test and repair time Increasing crew station automation Enhancing stealth operation Wide use of common modules (HW amp SW)) Ability to perform in-aircraft test and maintenance of avionics Use of VHSIC technology and Capability to operate over extended periods of time at austere
deployed locations and be maintainable without the Avionics Intermediate Shop
18 What do you mean by Engine control and managementEngine control and management monitors the engines condition automatically controls the flow of fuel and
respond to throttle command Control system It ensures the engine limits in terms of temperatures engine speeds and accelerations and the engines respond in an optimum manner to the throttle command
19 What do you mean by House keeping management The term house keeping management has been used to cover the automation of the background tasks which are essential for the aircrafts safe and efficient operation Such tasks include
Fuel management Electrical power supply system management Cabincockpit pressurization systems Environmental control system Warning systems Maintenance and monitoring systems
20 State the importance of Radar systemsInstalled in all civil airliners amp in many general aviation aircraft
bull To detect water droplets and provide warning of storms cloud turbulence and severe precipitation-aircraft can alter course and avoid such turbulent conditionsbull It should be noted that in severe turbulence the violence of the vertical gusts can subject the aircraft structure to very high loads and stresses These radars can also generally operate in ground mapping and terrain avoidance modes bull In the airborne interception mode the radar must be able to detect aircraft upto 100 miles away and track while scanning and keeping tabs on several aircraft simultaneously bull The radar must also have a look down capability and be able to track low flying aircraft below it
21 Write short notes on MIL STD 1553 MIL-STD-1553 is a military standard published by the United States Department of Defense that defines the
mechanical electrical and functional characteristics of a serial data bus It was originally designed as an avionic data bus for use with military avionics but has also become commonly used in spacecraft on-board data handling (OBDH) subsystems both military and civil It features multiple (commonly dual) redundant balanced line physical layers a (differential) network interface time division multiplexing half-duplex commandresponse protocol and can handle up to 31 remote terminals (devices) A version of MIL-STD-1553 using optical cabling in place of electrical is known as MIL-STD-1773
DrNGPInstitute of TechnologyCoimbatore - 48
22 Categorize the key elements of MIL STD 1553Some of the key MIL-STD-1553B elements are the bus controller the embedded remote terminal (a sensor or
subsystem that provides its own internal 1553 interface) the stand-alone remote terminal bus monitor and two other devices that are part of the 1553 integration the twisted shielded pair wire data bus and the isolation couplers that are optional
23 What is the purpose of Data Bus CouplerThe data bus coupler unit that isolates the main bus from the terminals MIL-STD-1553B allows two types of
data bus interface techniques direct coupling and transformer coupling Subsystems and 1553 bus elements are interfaced to the main data bus by interconnection buses (called ldquostubsrdquo) These stubs are either connected directly to the main bus or interfaced via data bus couplers The data bus couplers contain two isolation resistors (one per wire) and an isolation transformer (with a ratio of 1 to the square root of 2) The purpose of the data bus couplers is to prevent a short on a single stub from shorting the main data bus
24 Which types of coupling may be used in the ARINC 629 bus systemARINC 629 uses both current and voltage coupling modes of operation In current mode coupling the couplers
used are inductive in nature The current mode is advantageous than voltage mode as the bus wire does not have to be broken to insert the RT and if a unit is removed the bus does not have to be reconnected
25 Justify the need for label in an ARNIC 429 systemTransmission from the source LRU is comprised of 32 bit words containing a 24 bit data portion containing the
actual information and an 8 bit label describing the data itselfThe only two fields definitively required are the Label and the Parity bit leaving up to 23 bits available for higher resolution data representation Many non-standard word formats have been adopted by various manufacturers of avionics equipment Even with the variations included all ARINC data is transmitted in 32 bit words Any unused bits are padded with zeros
26 Illustrate ARINC 629 Bus system with its components
27 Infer and interpret the bit format of ARNIC 429
DrNGPInstitute of TechnologyCoimbatore - 48
28 What are the major drivers for avionics systems in a typical civil transport aircraftThe major drivers for avionics systems in a typical civil transport aircraft are Fly by Wire Flight Controls Full
Flight Regime 4 D Flight Management Full Glass Cockpits FANS capability to operate in a new air traffic management environment Passenger entertainment systems On board central Maintenance computers and electronic Documentation
29 Explain Cockpit A cockpit or flight deck is the area usually near the front of an aircraft from which a pilot controls the aircraft
Most modern cockpits are enclosed except on some small aircraft Most Airbus cockpits are glass cockpits featuring fly-by-wire technology The cockpit of an aircraft contains flight instruments on an instrument panel and the controls that enable the pilot to fly the aircraft In most airliners a door separates the cockpit from the aircraft cabin
30 What is the significance of PFDThe primary flight display is usually located in a prominent position either centrally or on either side of the
cockpit It will in most cases include a digitized presentation of the attitude indicator air speed and altitude indicators (usually as a tape display) and the vertical speed indicator It will in many cases include some form of heading indicator and ILSVOR deviation indicators In many cases an indicator of the engaged and armed auto flight system modes will be present along with some form of indication of the selected values for altitude speed vertical speed and heading It may be pilot selectable to swap with the ND
DrNGPInstitute of TechnologyCoimbatore - 48
UNIT II -
1 What is navigationNavigation is the determination of the position and velocity of the mass center of a moving vehicle The three components of position and the three components of velocity make up a six-component state vector that fully describes the translational motion of the vehicle because the differential equations of motion are of second order
2 What is Radio Navigation
Radio navigation or radio navigation is the application of radio frequencies to determine a position on the Earth Like radiolocation it is a type of radio determination The basic principles are measurements fromto electric beacons especially
directions eg by bearing radio phases or interferometry distances eg ranging by measurement of travel times partly also velocity eg by means of radio Doppler shift
3 What are the characteristics of Automation Detection FinderADF is the oldest radio navigation system still in use ADF uses Non-Directional Beacons (NDBs) that are
simply AM-radio transmitters operating in the Low and Middle Frequency (LMF) Band from 190 to 535 kHz These frequencies are below the standard broadcast band All ADFs can also home in on AM broadcast stations Pilots can listen to the radio and navigate also The ADF indicator has a compass rose and an indicating needle The needle automatically points to the station
4 State the functionality of DMEIn the post-war era a general navigation system using transponder-based systems was deployed as the distance
measuring equipment (DME) system DME was identical to Gee-H in concept but used new electronics to automatically
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
The hinged part of the vertical stabilizer is called the rudder it is used to deflect the tail to the left and right as viewed from the front of the fuselage The rudder input insures that the aircraft is properly aligned to the curved flight path during the maneuver The rudder works by changing the effective shape of the airfoil of the vertical stabilizer
13 List the steps in Pitch processA pitch motion is an up or down movement of the nose of the aircraftThe pitching motion is being caused by the
deflection of the elevator of this aircraft The elevator is a hinged section at the rear of the horizontal stabilizerThe pitch axis is perpendicular to the aircraft centerline and lies in the plane of the wings
14 What is the need for two different speeds in ARINC 429ARINC 429 specifies two speeds for data transmission Low speed operation is stated at 125 kHz with an actual
allowable range of 12 to 145 kHz High speed operation is 100 kHz plusmn 1 allowed These two data rates cannot be used on the same transmission bus
15 Justify the need for communication system in a civil transport aircraft Aircraft need to communicate and find out where they are and where they are going Most civil aircraft have a
VHF radio They communicate with the air traffic control in the 118 - 136 MHz band Additionally they might be equipped with HF radio this has greater range and typically used over oceans Commercial aircrafts use VHF but also have Satellite communications Military use VHF UHF and HF
16 Draw the roll axis and roll motion in an aircraft
17 Compare the different avionic systems and bring out their merits and demerits
Centralized Architecture Simple design Software can be written easily Computers are located in readily accessible bay
Disadvantages Requirement of long data buses Low flexibility in software Increased vulnerability to change Different conversion techniques are needed at the central computer
Federated Architecture Increased Information Fusion Higher levels and complexity of software Standardization for maintenance simplification Lower costs Backward and growth capability while making use of emerging technology ndash VHSIC Voice
DrNGPInstitute of TechnologyCoimbatore - 48
Recognition synthesis and Artificial Intelligence Provides capability for rapid flow of data in through and from the system as well as between and
within the system Higher levels of avionics integration and resource sharing of sensor and computational capabilities Pilot plays the role of a WEAPON SYSTEM MANAGER as opposed to subsystem
operatorinformation integrator Able to sustain operations with minimal support fly successful mission day and night in any type of
weather Face a numerically and technologically advanced enemy aircraft and defensive systems
Advantages Component reliability gains Use of redundancy and resource sharing Application of fault tolerance Reduction of maintenance test and repair time Increasing crew station automation Enhancing stealth operation Wide use of common modules (HW amp SW)) Ability to perform in-aircraft test and maintenance of avionics Use of VHSIC technology and Capability to operate over extended periods of time at austere
deployed locations and be maintainable without the Avionics Intermediate Shop
18 What do you mean by Engine control and managementEngine control and management monitors the engines condition automatically controls the flow of fuel and
respond to throttle command Control system It ensures the engine limits in terms of temperatures engine speeds and accelerations and the engines respond in an optimum manner to the throttle command
19 What do you mean by House keeping management The term house keeping management has been used to cover the automation of the background tasks which are essential for the aircrafts safe and efficient operation Such tasks include
Fuel management Electrical power supply system management Cabincockpit pressurization systems Environmental control system Warning systems Maintenance and monitoring systems
20 State the importance of Radar systemsInstalled in all civil airliners amp in many general aviation aircraft
bull To detect water droplets and provide warning of storms cloud turbulence and severe precipitation-aircraft can alter course and avoid such turbulent conditionsbull It should be noted that in severe turbulence the violence of the vertical gusts can subject the aircraft structure to very high loads and stresses These radars can also generally operate in ground mapping and terrain avoidance modes bull In the airborne interception mode the radar must be able to detect aircraft upto 100 miles away and track while scanning and keeping tabs on several aircraft simultaneously bull The radar must also have a look down capability and be able to track low flying aircraft below it
21 Write short notes on MIL STD 1553 MIL-STD-1553 is a military standard published by the United States Department of Defense that defines the
mechanical electrical and functional characteristics of a serial data bus It was originally designed as an avionic data bus for use with military avionics but has also become commonly used in spacecraft on-board data handling (OBDH) subsystems both military and civil It features multiple (commonly dual) redundant balanced line physical layers a (differential) network interface time division multiplexing half-duplex commandresponse protocol and can handle up to 31 remote terminals (devices) A version of MIL-STD-1553 using optical cabling in place of electrical is known as MIL-STD-1773
DrNGPInstitute of TechnologyCoimbatore - 48
22 Categorize the key elements of MIL STD 1553Some of the key MIL-STD-1553B elements are the bus controller the embedded remote terminal (a sensor or
subsystem that provides its own internal 1553 interface) the stand-alone remote terminal bus monitor and two other devices that are part of the 1553 integration the twisted shielded pair wire data bus and the isolation couplers that are optional
23 What is the purpose of Data Bus CouplerThe data bus coupler unit that isolates the main bus from the terminals MIL-STD-1553B allows two types of
data bus interface techniques direct coupling and transformer coupling Subsystems and 1553 bus elements are interfaced to the main data bus by interconnection buses (called ldquostubsrdquo) These stubs are either connected directly to the main bus or interfaced via data bus couplers The data bus couplers contain two isolation resistors (one per wire) and an isolation transformer (with a ratio of 1 to the square root of 2) The purpose of the data bus couplers is to prevent a short on a single stub from shorting the main data bus
24 Which types of coupling may be used in the ARINC 629 bus systemARINC 629 uses both current and voltage coupling modes of operation In current mode coupling the couplers
used are inductive in nature The current mode is advantageous than voltage mode as the bus wire does not have to be broken to insert the RT and if a unit is removed the bus does not have to be reconnected
25 Justify the need for label in an ARNIC 429 systemTransmission from the source LRU is comprised of 32 bit words containing a 24 bit data portion containing the
actual information and an 8 bit label describing the data itselfThe only two fields definitively required are the Label and the Parity bit leaving up to 23 bits available for higher resolution data representation Many non-standard word formats have been adopted by various manufacturers of avionics equipment Even with the variations included all ARINC data is transmitted in 32 bit words Any unused bits are padded with zeros
26 Illustrate ARINC 629 Bus system with its components
27 Infer and interpret the bit format of ARNIC 429
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28 What are the major drivers for avionics systems in a typical civil transport aircraftThe major drivers for avionics systems in a typical civil transport aircraft are Fly by Wire Flight Controls Full
Flight Regime 4 D Flight Management Full Glass Cockpits FANS capability to operate in a new air traffic management environment Passenger entertainment systems On board central Maintenance computers and electronic Documentation
29 Explain Cockpit A cockpit or flight deck is the area usually near the front of an aircraft from which a pilot controls the aircraft
Most modern cockpits are enclosed except on some small aircraft Most Airbus cockpits are glass cockpits featuring fly-by-wire technology The cockpit of an aircraft contains flight instruments on an instrument panel and the controls that enable the pilot to fly the aircraft In most airliners a door separates the cockpit from the aircraft cabin
30 What is the significance of PFDThe primary flight display is usually located in a prominent position either centrally or on either side of the
cockpit It will in most cases include a digitized presentation of the attitude indicator air speed and altitude indicators (usually as a tape display) and the vertical speed indicator It will in many cases include some form of heading indicator and ILSVOR deviation indicators In many cases an indicator of the engaged and armed auto flight system modes will be present along with some form of indication of the selected values for altitude speed vertical speed and heading It may be pilot selectable to swap with the ND
DrNGPInstitute of TechnologyCoimbatore - 48
UNIT II -
1 What is navigationNavigation is the determination of the position and velocity of the mass center of a moving vehicle The three components of position and the three components of velocity make up a six-component state vector that fully describes the translational motion of the vehicle because the differential equations of motion are of second order
2 What is Radio Navigation
Radio navigation or radio navigation is the application of radio frequencies to determine a position on the Earth Like radiolocation it is a type of radio determination The basic principles are measurements fromto electric beacons especially
directions eg by bearing radio phases or interferometry distances eg ranging by measurement of travel times partly also velocity eg by means of radio Doppler shift
3 What are the characteristics of Automation Detection FinderADF is the oldest radio navigation system still in use ADF uses Non-Directional Beacons (NDBs) that are
simply AM-radio transmitters operating in the Low and Middle Frequency (LMF) Band from 190 to 535 kHz These frequencies are below the standard broadcast band All ADFs can also home in on AM broadcast stations Pilots can listen to the radio and navigate also The ADF indicator has a compass rose and an indicating needle The needle automatically points to the station
4 State the functionality of DMEIn the post-war era a general navigation system using transponder-based systems was deployed as the distance
measuring equipment (DME) system DME was identical to Gee-H in concept but used new electronics to automatically
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
Recognition synthesis and Artificial Intelligence Provides capability for rapid flow of data in through and from the system as well as between and
within the system Higher levels of avionics integration and resource sharing of sensor and computational capabilities Pilot plays the role of a WEAPON SYSTEM MANAGER as opposed to subsystem
operatorinformation integrator Able to sustain operations with minimal support fly successful mission day and night in any type of
weather Face a numerically and technologically advanced enemy aircraft and defensive systems
Advantages Component reliability gains Use of redundancy and resource sharing Application of fault tolerance Reduction of maintenance test and repair time Increasing crew station automation Enhancing stealth operation Wide use of common modules (HW amp SW)) Ability to perform in-aircraft test and maintenance of avionics Use of VHSIC technology and Capability to operate over extended periods of time at austere
deployed locations and be maintainable without the Avionics Intermediate Shop
18 What do you mean by Engine control and managementEngine control and management monitors the engines condition automatically controls the flow of fuel and
respond to throttle command Control system It ensures the engine limits in terms of temperatures engine speeds and accelerations and the engines respond in an optimum manner to the throttle command
19 What do you mean by House keeping management The term house keeping management has been used to cover the automation of the background tasks which are essential for the aircrafts safe and efficient operation Such tasks include
Fuel management Electrical power supply system management Cabincockpit pressurization systems Environmental control system Warning systems Maintenance and monitoring systems
20 State the importance of Radar systemsInstalled in all civil airliners amp in many general aviation aircraft
bull To detect water droplets and provide warning of storms cloud turbulence and severe precipitation-aircraft can alter course and avoid such turbulent conditionsbull It should be noted that in severe turbulence the violence of the vertical gusts can subject the aircraft structure to very high loads and stresses These radars can also generally operate in ground mapping and terrain avoidance modes bull In the airborne interception mode the radar must be able to detect aircraft upto 100 miles away and track while scanning and keeping tabs on several aircraft simultaneously bull The radar must also have a look down capability and be able to track low flying aircraft below it
21 Write short notes on MIL STD 1553 MIL-STD-1553 is a military standard published by the United States Department of Defense that defines the
mechanical electrical and functional characteristics of a serial data bus It was originally designed as an avionic data bus for use with military avionics but has also become commonly used in spacecraft on-board data handling (OBDH) subsystems both military and civil It features multiple (commonly dual) redundant balanced line physical layers a (differential) network interface time division multiplexing half-duplex commandresponse protocol and can handle up to 31 remote terminals (devices) A version of MIL-STD-1553 using optical cabling in place of electrical is known as MIL-STD-1773
DrNGPInstitute of TechnologyCoimbatore - 48
22 Categorize the key elements of MIL STD 1553Some of the key MIL-STD-1553B elements are the bus controller the embedded remote terminal (a sensor or
subsystem that provides its own internal 1553 interface) the stand-alone remote terminal bus monitor and two other devices that are part of the 1553 integration the twisted shielded pair wire data bus and the isolation couplers that are optional
23 What is the purpose of Data Bus CouplerThe data bus coupler unit that isolates the main bus from the terminals MIL-STD-1553B allows two types of
data bus interface techniques direct coupling and transformer coupling Subsystems and 1553 bus elements are interfaced to the main data bus by interconnection buses (called ldquostubsrdquo) These stubs are either connected directly to the main bus or interfaced via data bus couplers The data bus couplers contain two isolation resistors (one per wire) and an isolation transformer (with a ratio of 1 to the square root of 2) The purpose of the data bus couplers is to prevent a short on a single stub from shorting the main data bus
24 Which types of coupling may be used in the ARINC 629 bus systemARINC 629 uses both current and voltage coupling modes of operation In current mode coupling the couplers
used are inductive in nature The current mode is advantageous than voltage mode as the bus wire does not have to be broken to insert the RT and if a unit is removed the bus does not have to be reconnected
25 Justify the need for label in an ARNIC 429 systemTransmission from the source LRU is comprised of 32 bit words containing a 24 bit data portion containing the
actual information and an 8 bit label describing the data itselfThe only two fields definitively required are the Label and the Parity bit leaving up to 23 bits available for higher resolution data representation Many non-standard word formats have been adopted by various manufacturers of avionics equipment Even with the variations included all ARINC data is transmitted in 32 bit words Any unused bits are padded with zeros
26 Illustrate ARINC 629 Bus system with its components
27 Infer and interpret the bit format of ARNIC 429
DrNGPInstitute of TechnologyCoimbatore - 48
28 What are the major drivers for avionics systems in a typical civil transport aircraftThe major drivers for avionics systems in a typical civil transport aircraft are Fly by Wire Flight Controls Full
Flight Regime 4 D Flight Management Full Glass Cockpits FANS capability to operate in a new air traffic management environment Passenger entertainment systems On board central Maintenance computers and electronic Documentation
29 Explain Cockpit A cockpit or flight deck is the area usually near the front of an aircraft from which a pilot controls the aircraft
Most modern cockpits are enclosed except on some small aircraft Most Airbus cockpits are glass cockpits featuring fly-by-wire technology The cockpit of an aircraft contains flight instruments on an instrument panel and the controls that enable the pilot to fly the aircraft In most airliners a door separates the cockpit from the aircraft cabin
30 What is the significance of PFDThe primary flight display is usually located in a prominent position either centrally or on either side of the
cockpit It will in most cases include a digitized presentation of the attitude indicator air speed and altitude indicators (usually as a tape display) and the vertical speed indicator It will in many cases include some form of heading indicator and ILSVOR deviation indicators In many cases an indicator of the engaged and armed auto flight system modes will be present along with some form of indication of the selected values for altitude speed vertical speed and heading It may be pilot selectable to swap with the ND
DrNGPInstitute of TechnologyCoimbatore - 48
UNIT II -
1 What is navigationNavigation is the determination of the position and velocity of the mass center of a moving vehicle The three components of position and the three components of velocity make up a six-component state vector that fully describes the translational motion of the vehicle because the differential equations of motion are of second order
2 What is Radio Navigation
Radio navigation or radio navigation is the application of radio frequencies to determine a position on the Earth Like radiolocation it is a type of radio determination The basic principles are measurements fromto electric beacons especially
directions eg by bearing radio phases or interferometry distances eg ranging by measurement of travel times partly also velocity eg by means of radio Doppler shift
3 What are the characteristics of Automation Detection FinderADF is the oldest radio navigation system still in use ADF uses Non-Directional Beacons (NDBs) that are
simply AM-radio transmitters operating in the Low and Middle Frequency (LMF) Band from 190 to 535 kHz These frequencies are below the standard broadcast band All ADFs can also home in on AM broadcast stations Pilots can listen to the radio and navigate also The ADF indicator has a compass rose and an indicating needle The needle automatically points to the station
4 State the functionality of DMEIn the post-war era a general navigation system using transponder-based systems was deployed as the distance
measuring equipment (DME) system DME was identical to Gee-H in concept but used new electronics to automatically
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
22 Categorize the key elements of MIL STD 1553Some of the key MIL-STD-1553B elements are the bus controller the embedded remote terminal (a sensor or
subsystem that provides its own internal 1553 interface) the stand-alone remote terminal bus monitor and two other devices that are part of the 1553 integration the twisted shielded pair wire data bus and the isolation couplers that are optional
23 What is the purpose of Data Bus CouplerThe data bus coupler unit that isolates the main bus from the terminals MIL-STD-1553B allows two types of
data bus interface techniques direct coupling and transformer coupling Subsystems and 1553 bus elements are interfaced to the main data bus by interconnection buses (called ldquostubsrdquo) These stubs are either connected directly to the main bus or interfaced via data bus couplers The data bus couplers contain two isolation resistors (one per wire) and an isolation transformer (with a ratio of 1 to the square root of 2) The purpose of the data bus couplers is to prevent a short on a single stub from shorting the main data bus
24 Which types of coupling may be used in the ARINC 629 bus systemARINC 629 uses both current and voltage coupling modes of operation In current mode coupling the couplers
used are inductive in nature The current mode is advantageous than voltage mode as the bus wire does not have to be broken to insert the RT and if a unit is removed the bus does not have to be reconnected
25 Justify the need for label in an ARNIC 429 systemTransmission from the source LRU is comprised of 32 bit words containing a 24 bit data portion containing the
actual information and an 8 bit label describing the data itselfThe only two fields definitively required are the Label and the Parity bit leaving up to 23 bits available for higher resolution data representation Many non-standard word formats have been adopted by various manufacturers of avionics equipment Even with the variations included all ARINC data is transmitted in 32 bit words Any unused bits are padded with zeros
26 Illustrate ARINC 629 Bus system with its components
27 Infer and interpret the bit format of ARNIC 429
DrNGPInstitute of TechnologyCoimbatore - 48
28 What are the major drivers for avionics systems in a typical civil transport aircraftThe major drivers for avionics systems in a typical civil transport aircraft are Fly by Wire Flight Controls Full
Flight Regime 4 D Flight Management Full Glass Cockpits FANS capability to operate in a new air traffic management environment Passenger entertainment systems On board central Maintenance computers and electronic Documentation
29 Explain Cockpit A cockpit or flight deck is the area usually near the front of an aircraft from which a pilot controls the aircraft
Most modern cockpits are enclosed except on some small aircraft Most Airbus cockpits are glass cockpits featuring fly-by-wire technology The cockpit of an aircraft contains flight instruments on an instrument panel and the controls that enable the pilot to fly the aircraft In most airliners a door separates the cockpit from the aircraft cabin
30 What is the significance of PFDThe primary flight display is usually located in a prominent position either centrally or on either side of the
cockpit It will in most cases include a digitized presentation of the attitude indicator air speed and altitude indicators (usually as a tape display) and the vertical speed indicator It will in many cases include some form of heading indicator and ILSVOR deviation indicators In many cases an indicator of the engaged and armed auto flight system modes will be present along with some form of indication of the selected values for altitude speed vertical speed and heading It may be pilot selectable to swap with the ND
DrNGPInstitute of TechnologyCoimbatore - 48
UNIT II -
1 What is navigationNavigation is the determination of the position and velocity of the mass center of a moving vehicle The three components of position and the three components of velocity make up a six-component state vector that fully describes the translational motion of the vehicle because the differential equations of motion are of second order
2 What is Radio Navigation
Radio navigation or radio navigation is the application of radio frequencies to determine a position on the Earth Like radiolocation it is a type of radio determination The basic principles are measurements fromto electric beacons especially
directions eg by bearing radio phases or interferometry distances eg ranging by measurement of travel times partly also velocity eg by means of radio Doppler shift
3 What are the characteristics of Automation Detection FinderADF is the oldest radio navigation system still in use ADF uses Non-Directional Beacons (NDBs) that are
simply AM-radio transmitters operating in the Low and Middle Frequency (LMF) Band from 190 to 535 kHz These frequencies are below the standard broadcast band All ADFs can also home in on AM broadcast stations Pilots can listen to the radio and navigate also The ADF indicator has a compass rose and an indicating needle The needle automatically points to the station
4 State the functionality of DMEIn the post-war era a general navigation system using transponder-based systems was deployed as the distance
measuring equipment (DME) system DME was identical to Gee-H in concept but used new electronics to automatically
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
28 What are the major drivers for avionics systems in a typical civil transport aircraftThe major drivers for avionics systems in a typical civil transport aircraft are Fly by Wire Flight Controls Full
Flight Regime 4 D Flight Management Full Glass Cockpits FANS capability to operate in a new air traffic management environment Passenger entertainment systems On board central Maintenance computers and electronic Documentation
29 Explain Cockpit A cockpit or flight deck is the area usually near the front of an aircraft from which a pilot controls the aircraft
Most modern cockpits are enclosed except on some small aircraft Most Airbus cockpits are glass cockpits featuring fly-by-wire technology The cockpit of an aircraft contains flight instruments on an instrument panel and the controls that enable the pilot to fly the aircraft In most airliners a door separates the cockpit from the aircraft cabin
30 What is the significance of PFDThe primary flight display is usually located in a prominent position either centrally or on either side of the
cockpit It will in most cases include a digitized presentation of the attitude indicator air speed and altitude indicators (usually as a tape display) and the vertical speed indicator It will in many cases include some form of heading indicator and ILSVOR deviation indicators In many cases an indicator of the engaged and armed auto flight system modes will be present along with some form of indication of the selected values for altitude speed vertical speed and heading It may be pilot selectable to swap with the ND
DrNGPInstitute of TechnologyCoimbatore - 48
UNIT II -
1 What is navigationNavigation is the determination of the position and velocity of the mass center of a moving vehicle The three components of position and the three components of velocity make up a six-component state vector that fully describes the translational motion of the vehicle because the differential equations of motion are of second order
2 What is Radio Navigation
Radio navigation or radio navigation is the application of radio frequencies to determine a position on the Earth Like radiolocation it is a type of radio determination The basic principles are measurements fromto electric beacons especially
directions eg by bearing radio phases or interferometry distances eg ranging by measurement of travel times partly also velocity eg by means of radio Doppler shift
3 What are the characteristics of Automation Detection FinderADF is the oldest radio navigation system still in use ADF uses Non-Directional Beacons (NDBs) that are
simply AM-radio transmitters operating in the Low and Middle Frequency (LMF) Band from 190 to 535 kHz These frequencies are below the standard broadcast band All ADFs can also home in on AM broadcast stations Pilots can listen to the radio and navigate also The ADF indicator has a compass rose and an indicating needle The needle automatically points to the station
4 State the functionality of DMEIn the post-war era a general navigation system using transponder-based systems was deployed as the distance
measuring equipment (DME) system DME was identical to Gee-H in concept but used new electronics to automatically
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
UNIT II -
1 What is navigationNavigation is the determination of the position and velocity of the mass center of a moving vehicle The three components of position and the three components of velocity make up a six-component state vector that fully describes the translational motion of the vehicle because the differential equations of motion are of second order
2 What is Radio Navigation
Radio navigation or radio navigation is the application of radio frequencies to determine a position on the Earth Like radiolocation it is a type of radio determination The basic principles are measurements fromto electric beacons especially
directions eg by bearing radio phases or interferometry distances eg ranging by measurement of travel times partly also velocity eg by means of radio Doppler shift
3 What are the characteristics of Automation Detection FinderADF is the oldest radio navigation system still in use ADF uses Non-Directional Beacons (NDBs) that are
simply AM-radio transmitters operating in the Low and Middle Frequency (LMF) Band from 190 to 535 kHz These frequencies are below the standard broadcast band All ADFs can also home in on AM broadcast stations Pilots can listen to the radio and navigate also The ADF indicator has a compass rose and an indicating needle The needle automatically points to the station
4 State the functionality of DMEIn the post-war era a general navigation system using transponder-based systems was deployed as the distance
measuring equipment (DME) system DME was identical to Gee-H in concept but used new electronics to automatically
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
measure the time delay and display it as a number rather than having the operator time the signals manually on an oscilloscope This led to the possibility that DME interrogation pulses from different aircraft might be confused but this was solved by having each aircraft send out a different series of pulses which the ground-based transponder repeated back
5 Write short notes on VORThe VOR station transmits two signals one is constant in all directions and the other varies the phase relative to
the first signal The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or radials from the VOR
6 List the procedure of Instrument Landing SystemAn aircraft on an instrument landing approach has a cockpit with computerized instrument landing equipment
that receives and interprets signals being from strategically placed stations on the ground near the runway This system includes a Localizer beam that uses the VOR indicator with only one radial aligned with the runway The Localizer beams width is from 3deg to 6deg It also uses a second beam called a glide slope beam that gives vertical information to the pilot
7 How ADF can be executed by homingThe ADF may be used to home in on a station Homing is flying the aircraft on the heading required to keep the
needle pointing directly to the 0deg (straight ahead) position To home into a station tune the station identify the Morse code signal then turn the aircraft to bring the ADF azimuth needle to the 0deg position Turn to keep the ADF heading indicator pointing directly ahead Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind and will have to fly further and for longer than the direct track
8 Define Glide Slope and glide Slope BeamThe angle between the local horizontal and the glide path of an aircraft It provides vertical guidance for aircraft
during approach and landing either using visual ground aids or onboard electronic componentsA directed radio wave emanating from a glideslope transmitter located near the approach end of the runway of an
instrumented airport to provide an indication of the minimum approach angle that will clear all obstacles to the runway
9 Where does marker beacon is usedMarker Beacon is a radio navigation aid used in the approach zone of an instrumented airport As the airplane
crosses over each of three marker beacon transmitters the pilot receives an accurate indication of the airplanes distance from the runway through the medium of a flashing light an aural signal
10 What is triangulationThe process of determining the distance between points on the earths surface or the relative positions of points
by dividing up a large area into a series of connected triangles measuring a base line between two points and then locating a third point by computing both the size of the angles made by lines from this point to each end of the base line and the lengths of these lines
11 Explain LORANLong range navigation is a hyperbolic radio navigation system developed in the United States during World War II It is similar to the UKs Gee system but operated at lower frequencies in order to provide improved range up to 1500 miles (2400 km) with accuracy of tens of miles It was first used for ship convoys crossing the Atlantic Ocean and then by long-range patrol aircraft but found its main use on the ships and aircraft operating in the Pacific theatre LORAN in its original form was an expensive system to implement requiring a cathode ray tube (CRT) display
12 Classify the ranges of LORAN StationsLORAN stations were built in pairs one master and one slave typically separated by about 600 miles (970 km) Each pair broadcast on one of four frequencies 175 185 19 or 195 MHz (as well as the unused 75 MHz) In any given location it was common to be able to receive more than three stations at a time so some other means of identifying the pairs was needed LORAN adopted the use of varying the pulse repetition frequency (PRF) for this task with each station sending out a string of 40 pulses at either 333 or 25 pulses per second
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
13 How tracking is established in ADF The ADF may also be used to track a desired course using an ADF and allowing for winds aloft winds which may blow the aircraft off-course Good pilotage technique has the pilot calculate a correction angle that exactly balances the expected crosswind As the flight progresses the pilot monitors the direction to or from the NDB using the ADF adjusts the correction as required A direct track will yield the shortest distance and time to the ADF location
14 State the importance of LORAN C stationsThe Loran C system consists of transmitting stations which are placed several hundred miles apart and organized into chains Within a Loran chain one station is designated as the master station and the others as secondary stations EveryLoran chain contains at least one master station and two secondary stations in order to provide two lines of position The master and secondary stations transmit radio pulses at precise time intervals A Loran receiver measures the time difference (TD) between when the vessel receives the master signal and when it receives each of the secondary signals When this elapsed time is converted to distance the locus of points having the same TD between the master and each secondary forms the hyperbolic LOP The intersection of two or more of these LOPrsquos produces a fix of the vesselrsquos position
15 Describe the history of DECCAThe Decca Navigator System was a hyperbolic radio navigation system which allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons The system used low frequencies from 70 to 129 kHz It was first deployed by the Royal Navy during World War II when the Allied forces needed a system which could be used to achieve accurate landings After the war it was extensively developed around the UK and later used in many areas around the world
16 What are the applications of radar ƒMilitary ƒ Remotesensing ƒ Air traffic control (ATC) ƒ Law enforcement and highway safety ƒ Aircraft safety and Navigation ƒ Ship safety ƒ Space
17 What is a radome A typical ground based metal space frame radome might have a two-way transmission loss of 12 db at frequency ban from L to X band
18 What are the advantages of OMEGA system 1 At low frequency in the 10KHZ range the coverage is increased 2 Loss of power at this frequency is low
19 What are the disadvantages of ILS 1 Provides a single approach path along the extended centre line of the runway2 It is site sensitive and subject to distortion and bending of the approach path due to site irregularities
20 What are the basic elements of a MLS system 1 Azimuth beam equipment 2 Elevation beam equipment 3 Distance measuring equipment
21 What is meant by Doppler navigation It employs the Doppler Effect to determine the velocity of the craft in a frame of coordinates fixed with respect
to the aircraft
22 What are the basic radar measurements that can be achieved from a Distributed target 1Size and shape
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
2Symmetry 3Radial Profile 4Tangential Profile
23 What is the purpose of radomeA radome (which is a portmanteau of radar and dome) is a structural weatherproof enclosure that protects a microwave (eg radar) antenna The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna In other words the radome is transparent to radar or radio waves Radomes protect the antenna surfaces from weather and conceal antenna electronic equipment from public view They also protect nearby personnel from being accidentally struck by quickly rotating antennas
24 State the functionality of Localizer in ILSOne of the main components of the ILS system is the localizer which handles the guidance in the horizontal
plane The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (10810 divide 11195 MHz) however the frequencies of the localizer are only placed on odd decimals with a channel separation of 50 kHz The trasmitter or antenna is in the axis of the runway on itrsquos other end opposite to the direction of approach A backcourse localizer is also used on some ILS systems
25 Describe Instrument Landing systemAn Instrument Landing System is a precision runway approach aid employing two radio beams to provide pilots with vertical and horizontal guidance during the landing approach The localiser (LOC)provides azimuth guidance while the glideslope (GS) defines the correct vertical descent profile Marker beacons and high intensity runways lights may also be provided as aids to the use of an ILS although the former are more likely nowadays to have been replaced by a DME integral to the ILS or one otherwise located on the aerodrome for example with a VOR
26 Outline the working characteristics of MLSThe microwave landing system (MLS) gets rid of some of the disadvantages of the ILS system It works for angles from minus40 to 40 horizontally (with respect to the runway) and from 0 to 20 vertically Its range is 20NM up to a maximum height of 20000f t And it uses a time-reference scanning beam (TRSB)
27 How does the TRSB work TRSB is based on a rotating antenna Most of the time this antenna is pointing at the 40 direction But in regular intervals it sweeps to the minus40 line and back again An airplane in the corresponding region is thus lsquohitrsquo twice by the signal Based on the time between these two hits the azimuth angle θ can be found
28 What is VOR NavigationVOR uses VHF radio waves (108ndash11795 MHz) with 50 kHz separation between each channel This keeps atmospheric interference to a minimum but limits the VOR to line-of-sight usage To receive VOR VHF radio waves generally a V-shaped horizontally polarized bi-pole antenna is used A typical location for the V dipole is in the vertical fin Other type antennas are also certified
29 State the components of MLSThe MLS system is comprised of ground pieces of equipment that are divided into the protractor components rangefinder components and the onboard hardware The information about the angles of the approach course descent flare and the course of an unsuccessful approach are acquired through an onboard antenna or the aircraft itself by measuring the time between two passages of an oscillating lobe of a high frequency signal The distance is determined with the help of an ancillary device the DME rangefinder The ground equipment consists in the basic configuration of an Azimuth Transmitter (AZ) with an added DME rangefinder perhaps even a more precise DMEP in close distance of a course transmitter and near an elevation transmitter
30 State the Principle of operation of MLSThe MLS system operates at a frequency band of 50310 ndash 50907 MHz on two separate channels at a mutual interval of 300 kHz The protractor part of the MLS system provides continually information about an aircraftrsquos position relative to the runway both in the vertical and horizontal plane The rangefinder part enables to measure the distance between an aircraft and the reference points in the approach process The angular information for the approach course descent flare
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
and go-around is determined by measuring the interval between two passages of an oscillating plane lobe through an onboard MLS antenna
Unit III ndash Inertial and satellite Navigation Systems
1 What are the essential elements of the spatial reference system
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
The essential elements of the spatial reference system or heading reference system (AHRS) are gyros and accelerometers They largely determine the performance and accuracy of these systems and account for a major part of the system cost
2 Explain the importance of Inertial Navigation systemAn inertial navigation system (INS) is a navigation aid that uses a computer motion sensors (accelerometers)
and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position orientation and velocity (direction and speed of movement) of a moving object without the need for external references It is used on vehicles such as ships aircraft submarines guided missiles and spacecraft as well as on the Lamborghini Huracaacuten
3 How gyroscope is used for measurement of orientation Gyroscopes measure the angular velocity of the system in the inertial reference frame By using the original orientation of the system in the inertial reference frame as the initial condition and integrating the angular velocity the systems current orientation is known at all times This can be thought of as the ability of a blindfolded passenger in a car to feel the car turn left and right or tilt up and down as the car ascends or descends hills Based on this information alone the passenger knows what direction the car is facing but not how fast or slow it is moving or whether it is sliding sideways
4 Tabulate the accuracy requirements for a typical FBW flight control system
SNo Component Parameters Flight Control System
Strapdown INS
1 Gyro Scale factor 05 0001 (10 ppm)Zero offsetrate uncertainty
1 min 001 hour
2 Acctr Scale factor 05 001 (100 ppm)Zero offsetrate uncertainty
510-3 g 510-5 g (50μg)
5 What is Inertial Measurement UnitAn Inertial Measurement Unit (IMU) is an electronic device that measures and reports a crafts velocity orientation and gravitational forces using a combination of accelerometers and gyroscopes sometimes also magnetometers IMUs are typically used to maneuver aircraft including unmanned aerial vehicles (UAVs) among many others and spacecraft including satellites and landers Recent developments allow for the production of IMU-enabled GPS devices An IMU allows a GPS receiver to work when GPS-signals are unavailable such as in tunnels inside buildings or when electronic interference is present
6 State the principle of codeless Differential GPSThis technique relies on bypassing the PRN codes entirely and using only the high resolution carriers Differential carrier phase tracking consists of measuring the phase shift between the same signal received at two different locations The phase shift is a direct measure of the difference in path length from the satellite to each antenna
7 Write short notes on accelerometersAn accelerometer is a device that measures proper acceleration (g-force) Proper acceleration is not the same as coordinate acceleration (rate of change of velocity) For example an accelerometer at rest on the surface of the Earth will measure an acceleration g= 981 ms2 straight upwards By contrast accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero
8 List the major disadvantages of IMUThe major disadvantage of using IMUs for navigation is that they typically suffer from accumulated error including Abbe error Because the guidance system is continually adding detected changes to its previously-calculated positions
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
any errors in measurement however small are accumulated from point to point This leads to drift or an ever-increasing difference between where the system thinks it is located and the actual location
9 Enumerate the applications of accelerometersAccelerometers can be used to measure vibration on cars machines buildings process control systems and safety installations They can also be used to measure seismic activity inclination machine vibration dynamic distance and speed with or without the influence of gravity Applications for accelerometers that measure gravity wherein an accelerometer is specifically configured for use in gravimetry are called gravimeters
10 Infer and interpret the technique of complementary filteringInertial velocity mixing exploits the technique of complementary filtering for combining the data from two independent sources of information Other examples include
1 Combining a magnetic heading reference with a gyro heading reference2 Combining barometrically measured altitude or radar altimeter measured altitude with inertially derived
altitude
11 Summarize the importance of strapdown systemsStrapdown systems get their name from the fact that they strap the sensors directly to the vehicle chassis eliminating the platform gimbals at the cost of causing the components to suffer the dynamic rotation of the vehicle Strapdown mechanization places more stringent requirements on the sensory components used and on the computational throughput so these systems have appeared relatively recently in the history of development of inertial navigation Such systems promise to replace semi-analytic systems in most applications
12 What is direction cosine matrixThese systems are analysed mathematically in an identical manner to gimballed systems with the exception that the accelerometer readouts are first converted to a common coordinate system using a matrix transformation often called the direction cosine matrix
13 State the principle of strapdown systemsThe operating principle is to use very high speed rebalance loops which continually torque the gyros back to their null vehicle aligned positions The effort required to do this is proportional to the angular rate of the vehicle The rebalance loops report current level of effort to the computational stabilization algorithm which maintains the current vehicle orientation in inertial space
14 How will you implement inertial navigation systems by accounting its characteristicsThe implementation of a particular navigation coordinate system involves either actively controlling or passively keeping track of the orientation of the accelerometers as the vehicle moves A trade-off exists between mechanical complexity and computational complexity which over time has tended to drive system designs toward computational complexity as computer systems have improved in performance
15 Compare and contrast AHRS Doppler reference systems and Inertial navigation systems
Air Data based DR Navigation Dopplerheading reference systems Inertial navigation systemsThe basic information used comprises the true airspeed (from the air data computer) with wind speed and direction (forecast or estimated) and the aircraft heading from the attitude Heading
These use a Doppler Radar velocity sensor system to measure the aircrafts ground speed and drift angle The aircraft heading is provided by AHRS
These derive the aircrafts velocity components by integrating the horizontal components of the aircrafts acceleration with respect to time These components are computed from the outputs of very
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
Reference System high accuracy gyroscopes and accelerometers which measure the aircrafts angular and linear motion
16 Summarize the main position fixing navigation systems in current scenario1 Range and Bearing Radio Navigation aids2 Satellite Navigation Systems ndash GPS( Global Position System)3 Terrain Reference Navigation System
17 Draw the navigation information flow to user systems incorporating sensor systems data and navigation systems
18 What are the quantities required to formulate the basic principle of DR Navigation system 1 Initial Position ndash latitudelongitude2 The northerly and easterly velocity components of aircraft VN and VE
Derivation of rate of change of latitude and longitude
19 Summarize the attributes of an ideal navigation and guidance system for military applications
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
1 High accuracy2 Self-contained3 Autonomous- does not depend on other systems4 Passive ndash does not radiate5 Unjammable6 Does not require reference to the ground or outside world
20 What are gimbaled systemsA gimbal is a rigid with rotation bearings for isolating the inside of the frame from external rotations about the bearing axes At least three gimbals are required to isolate a subsystem from host vehicle rotations about three axes typically labeled roll pitch and yaw axes The gimbals in an INS are mounted inside one another Gimbals and torque servos are used to null out the rotation of stable platform on which the inertial sensors are mounted
21 How does gimbaled INS work The gyros of a type known as ldquointegrating gyrosrdquo give an output proportional to the angle
through which they have been rotated Output of each gyro connected to a servomotor driving the appropriate gimbal thus keeping the gimbal in a constant orientation in inertial space The gyros also contain electrical torque generators which can be used to create a fictitious
input rate to the gyros Applications of electrical input to the gyro torque generatorscause the gimbaltorque motorsservos to null the diff
erence between the true gyro input rate and the electrically applied bias rate This forms a convenient means of cancelling out any drift errors in the gyro
22 Draw the block diagram of Strap Down Inertial navigation system
23 What are the components of Strap Down INS building blocksThe Components of a Strapdown Navigation System are
instrument cluster instrument electronics attitude computer
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
navigation computer
These units will be mounted in a case together with the necessary electrical power supplies and interface electronics which may then be installed in a vehicle requiring an on-board navigation capability Whilst it is often assumed that the unit will be fixed rigidly in the vehicle it is usually necessary for it to be installed on anti-vibration (AV) mounts to provide isolation from vehicle motion at frequencies to which the unit is particularly sensitive
24 How will you overcome the difficulty in polar navigational capability1 A spherical coordinate system with the poles removed to some other regions2 A lsquounipolarrsquo system3 Direction Cosines
25 List the advantages of INS1 It is autonomous and does not rely on any external aids or visibility conditions It can operate in
tunnel or underwater as well as anywhere else 2 It is inherently well suited for integrated navigation guidance and control of the host vehicle Its IMU measures the derivatives of the variables to be controlled (eg position velocity and attitude)3 It is immune to jamming and inherently stealthy It neither receivers nor emits detectable radiation and requires no external antenna that might be detectable by radar
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
Unit IV
1 What is air speed indicatorThe airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the crafts airspeed typically in knots to the pilot In its simplest form an ASI measures the difference in pressure between that which is generally around the craft and the increased pressure caused by propulsion The needle tracks pressure differential but the dial is marked off as airspeed
2 Draw and label the basic air data system
3 Derive the other air data quantities from Static Pressure and Total PressureFrom the measurements of static pressure PS and the total pressure PT it is possible to drive the following quantities Pressure altitude (HP) Vertical speed (HP) Calibrated airspeed (VC) Mach Number (M)
4 What is indicated air temperatureIndicated or measured air temperature Tm is sensed by means of a temperature sensor installed in a probe in the
airstream This gives a measure of airstream temperature TS plus the kinetic rise in temperature due to the air being brought partly or wholly to rest relative to temperature sensing probe
5 Sketch the block diagram flow of air data indicating the key to avionic sub-systems
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
6 Give a short description of the measurement of air data quantitiesThe air data quantities pressure altitude vertical speed calibrated airspeed true airspeed Mach number etc are derived from three basic measurements by sensors connected to probes which measure
Total (or pilot) Pressure Static Pressure Total (or indicated) pressure
7 Differentiate Pilot Pressure and Static PressureThe pitot or total pressure is the sum of the static pressure and the pressure rise resulting from stagnation of the airflow (dynamic pressure) in the pitot tube Total pressure is generally easy to measure accurately the location is not critical as long as the tube opening is outside the aircrafts boundary layer and is oriented to the incoming flow For well-sited or aligned probes the total pressure error is usually negligible Static pressure can be measured with a pitot-static tube or a flush-mounted port on the fuselage
8 State the significance of GPS receiverA GPS receiver can determine the time position and velocity of an airplane without drift errors Position data from a GPS receiver may be degraded by selective availability when a nonmilitary receiver is used Velocities are not affected by this problem Using differential GPS greatly increases position accuracy but a reference ground receiver is needed These GPS data are typically received on the order of 1 sample per second The Euler angles of the airplane can be measured using multiple GPS antennae on the airplane and the carrier phase of the GPS signal
9 What is density altitudeDensity altitude is defined as the altitude at which the density of the International Standard Atmosphere (ISA) is the same as the density of the air being evaluated (The Standard Atmosphere is simply a mathematical model of the atmosphere which is standardized so that predictable calculations can be made)
10 What is a stall warning indicator and Minimum Safe Altitude WarningSTALL-WARNING INDICATOR is a flight instrument that warns the pilot that his airplane is approaching a stall Minimum Safe Altitude Warning (MSAW) is a ground-based safety net intended to warn the air traffic controller (ATCO) about the increased risk of controlled flight into terrain by generating in a timely manner an alert of aircraft proximity to terrain or obstacles The main purpose of MSAW is to enhance safety and not to monitor adherence to any specified minima In practice MSAW is a part of the ATC system and from this perspective it can be regarded as a ldquofunctionrdquo
11 Define autopilot What is the basic function of autopilotThe basic function of autopilot is to control the flight of the aircraft and maintain it on a pre-determined path in space without nay action being required by the pilot The autopilot can thus relieve the pilot from fatigue ad tedium of having to
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
maintain continuous control of the aircrafts flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission
12 List some of the functions of FMS Automatic Navigation and guidance including lsquo4Drsquo navigation Presentation of information Management of aircraft systems Efficient management of fuel Reduction of operating costs
13 Explain the inner and outer loops of autopilotThe pitch attitude control loop and the heading control loop with its inner loop commanding the aircraft bank angle are the fundamental inner loops in most autopilot control modes The outer autopilot loop is thus essentially a slower longer period control loop compared with the inner flight control loops which are faster shorter period loops
14 State the functionality of Heading control autopilotThe function of the heading control mode of the autopilot is to automatically steer the aircraft along a particular set direction
15 What is Mach Number and true air speedThe true airspeed (TAS also KTAS for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying The true airspeed is important information for accurate navigation of an aircraft The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects Because of the importance of this speed ratio aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach a late 19th century physicist who studied gas dynamics
16 Give the formaulas for calculating true airspeed of low and high speed flightsLow-speed flightAt low speeds and altitudes IAS and CAS are close to equivalent airspeed (EAS) TAS can be
calculated as a function of EAS and air density
where
is true airspeed
is equivalent airspeed
is the air density at sea level in the International Standard Atmosphere (15 degC and 101325
hectopascals corresponding to a density of 1225 kgm3)
is the density of the air in which the aircraft is flyingHigh-speed flight
TAS can be calculated as a function of Mach number and static air temperature
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
where
is the speed of sound at standard sea level (66147 knots (122504 kmh 34029 ms))
is Mach number
is static air temperature in kelvins
is the temperature at standard sea level (28815 K)
17 Sketch the ILS Localiser coupling loop of the autopilot
18 What are the two alternatives for effecting a safe landing A fully automatic landing system with the autopilot controlling the landing to touchdown A very high integrity
autopilot system is required with the failure survival capability provided by the redundancy such that the probability of catastrophic failure is less than 10-7hour
The use of an enhanced vision system with a HUD using a millimetric wavelength radar sensor in the aircraft to derive a synthetic runaway image
19 Draw the block diagram of ILS Glide slope coupling loop
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
20 Outline the phases in BLEU automatic Landing System1 Final Approach2 Constant Attitude3 Flare4 Kick off Drift
These phases are required for the BLEU ALS to operate from the time the outer marker radio beacon is reached about 8000m from the threshold
21 Write the mathematical formula for describing the exponential flare manoeuvre
Hrsquo = -KHWhere K is a constant and H is the aircraft height above the ground
The control law used for autoflare isH+THrsquo=HREF
Where HREF is a small negative height or bias which ensures there is still a small downwards velocity at touchdown
22 What are the tasks carried out by Flight Management System1 Flight Guidance and lateral and vertical control of the aircraft flight path
23 Justify the validation of ILS Guidance
An ILS is only valid if used within strict boundaries either side of the transmitted LOC and GS beams as documented on the corresponding AIP Instrument Approach Procedure (IAP) From a pilot perspective these limits are defined as Full Scale Deflection (FSD) of the deviation indication on the ILS displays in the flight deck since once the deviation in respect of either the LOC or GS reaches FSD it becomes impossible to know the extent of the deviation
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
Because of this pilots navigating their aircraft onto an ILS whether from below the GS or above have always been expected when acquiring an ILS GS to cross-check their range from touchdown against their indicated altitudeheight and confirm that their aircraft is on the promulgated IAP GS
UNIT V- AIRCRAFT DISPLAYS
1 What is meant by Flat Panel Display
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
Flat panel displays encompass a growing number of electronic visual display technologies They are far lighter and thinner than traditional television sets andvideo displays that use cathode ray tubes (CRTs) and are usually less than 10 centimeters (39 in) thick Flat panel displays can be divided into two general display device categories volatile and static In many applications specifically modern portable devices such as laptops mobile phones digital cameras camcorders point-and-shoot cameras and pocket video cameras any display disadvantages are made up for by portability advantages
2 Define Glass cockpit A glass cockpit is an aircraft cockpit that features electronic instrument displays Where a traditional cockpit relies on numerous mechanical gauges to display information a glass cockpit uses several displays driven by flight management systems that can be adjusted to display flight information as needed This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information They are also popular with airline companies as they usually eliminate the need for a flight engineer In recent years the technology has become widely available in small aircraft
3 Define plasma panel
A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32 inches or larger) Many tiny cells between two panels of glass hold a mixture of noble gases The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light
4 Differentiate LED amp LCD
LEDs are based on the semiconductor diode When the diode is forward biased (switched on) electrons are able to recombine with holes and energy is released in the form of light This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor LEDs present many advantages over traditional light sources including lower energy consumption longer lifetime improved robustness smaller size and faster switching
5 Explain CRT and its usage in aircraft displays
The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen with internal or external means to accelerate and deflect the electron beam used to create images in the form of light emitted from the fluorescent screen
6 What is meant by DVI
The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors It was developed by an industry consortium the Digital Display Working Group (DDWG) It is designed for carrying uncompressed digital video data to a display
7 What are MFD and its significance in Aircraft
A Multi-function display (MFD) is a small screen (CRT or LCD) in an aircraft surrounded by multiple buttons that can be used to display information to the pilot in numerous configurable ways Often an MFD will be used in concert with a Primary Flight Display MFDs are part of the digital era of modern planes or helicopter The first MFD were introduced by airforces The advantage of an MFD over analog display is that an MFD does not consume much space in the cockpit Many MFDs allow the pilot to display their navigation route moving map weather radar NEXRAD GPWS TCAS and airport information all on the same screen
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
8 What is HOTAS
HOTAS an abbreviation for Hands On Throttle-And-Stick is the name given to the concept of placing buttons and switches on the throttle stick and flight control stick in an aircrafts cockpit allowing the pilot to access vital cockpit functions and fly the aircraft without having to remove his hands from the throttle and flight controls Having all switches on the stick and throttle allows the pilot to keep his hands on throttle-and-stick thus allowing him to remain focused on more important duties than looking for controls in the cockpit
9 Explain Head Up Display
A head-up display or abbreviated as HUD is any transparent display that presents data without requiring the user to look away from his or her usual viewpoint The origin of the name stems from the user being able to view information with his head up and looking forward instead of angled down looking at lower instruments Although they were initially developed for military aviation HUDs are now used in commercial aircraft automobiles and other applications
10 What is usage of night vision goggles bull Night time flight is possible (As pilot can see the terrain like a near morning) bull Close Ground Support during night time attack is enabled in rotor and fighter planes bull Night time reconnaissance and surveillance is possible on NVG enabled cameras
11 Explain advantage of EL over Plasma display bull Less flickering bull Sustainable luminosity even during aging bull Light weight than plasma displays bull Simple light weight component bull Available in smaller size (unlike plasma displays which are available only at 32rdquo)
12 Explain the advantage of HMD over MUD bull In HMD the gimbaled sensors enables the pilot to watch critical data in the helmet in the directions through which heshe moveslooks thus facilitating himher to watch the primary data always bull HMD display formats are very similar to those of HUDs except for the addition of helmet-pointing azimuth and elevation information and vectors showing where the last target of interest was prior to looking down into the cockpit or searching for another target
13 Explain MFK and its usage bull As the cockpits of modern aircraft have more controls jammed into them the point reached where there is no more space Multifunction keyboards (MFKs) offer a very attractive solution to this space problem wherein a single panel of switches performs a variety of functions depending on the phase of the mission or the keyboard menu selected bull Multifunction keyboards can be implemented in several ways The first two ways use LEDs or LCDs in panels in a central location Designs using LEDs have arrays (typically ranging from five rows of three switches to seven rows of five switches) of standard sized push button switches with legends built into the surface of the switches
14 What is FBLFBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
15 Explain FBL over FBWbull FBW (FLY BY WIRE) Itrsquos a concept of utilizing digital data bus for the transmission of mechanical movements from pilotrsquos joystick to the Mechanical actuators near by the control surface in the form of electronic signals using
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
suitable transducers It eliminates majority of the weight in handling control rods push pull systems Because of this weight elimination the redundancy level of FBW can be raised bull FBL (FLY BY LIGHT) Itrsquos a concept of utilizing optic fiber cables for the transmission of mechanical movements from pilotrsquos joystick to the mechanical actuators near by the control surface in the form of monochromatic light signals using suitable transducers It eliminates the amplification units filter circuits modulator units etc which are at high redundant levels in the FBW FBL is more reliable and the signals passing through the fiber optic cable never degrade and hence it contributes further low weight in the aircraft
16 Give few examples of integrated avionics system used in weapon system bull Hemet Mounted Display (HMT) bull Head Level Display (HLD) bull Night Vision Goggles (NGV) bull Forward Looking Infra Red Displays (FLIR)
17 Explain Electronic warfare Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum or to attack the enemy The purpose of electronic warfare is to deny the opponent the advantage of and ensure friendly unimpeded access to the EM spectrum EW can be applied from air sea land and space by manned and unmanned systems and can target communication radar or other services EW includes three major subdivisions Electronic Attack (EA) Electronic Protection (EP) and Electronic warfare Support (ES)
18 Head up Displays are now being installed in civil aircrafts JustifyHead Up Displays have inherent advantages of head up presentation of primary flight information including depiction of the aircrafts flight path vector resulting in improved situational awareness and increased safety in circumstances such as wind shear or terrain traffic avoidance manoeuvresEnhanced vision using a raster mode HUD to project a FLIR video picture of the outside world from a FLIR sensor installed in the aircraft will enable the pilot to land the aircraft in conditions of very low or Zero visibility at airfields
19 What is the working principle of CollimatorCollimator is defined as an optical system of finite focal length with an image source at the focal plane Rays of light emanating from a particular point on the focal plane exit from the collimating system as a parallel bunch of rays as if they came from a source at infinity
20 What is meant by Holographic HUDsHolographic HuDs use reflection holograms which depend for their operation on refractive index variations produced within a thin gelatin film sandwiched between two sheets of glass This is really a diffraction grating and hence more accurate name for such HUDs is diffractive HUDs
21 What are the factors that determine the Aircrew Helmet Design accuracy - what is the angular error between the pilots line-of-sight and the derived measurement slew rate - what is the maximum angular rate at which the pilot can slew his helmet and the system still
produce an accurate measurement field of regard - what is the angular range over which the sight can still produce a suitably accurate
measurement weight and balance - how heavy is the helmet and sight assembly where is its centre of gravity how will it
affect pilot fatigue levels in high G manoeuvre and does it pose a safety problem during ejection optical characteristics - is the pilots sighting reticle focussed at infinity How accurately can the sight be
calibrated Is the symbology sharp robustness - can the design handle the wear and tear of day to day combat squadron operations safety - how easily can the helmet be disconnected from the aircrafts systems during an ejection flexibility - can the design be used for other purposes like the display of symbology and imagery cost - how expensive is the HMSHMD and its supporting electronics and the integration of these into the
aircrafts weapon system
22 List the ways in which optical tracking system worksPattern recognition using a CCD Camera
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
25
DrNGPInstitute of TechnologyCoimbatore - 48
Detection of LEDs mounted on the helmetSophisticated measurement of laser generated fringing patterns
23 Illuatrate the use of BHMD as an impact on the next generation aircraft cockpit
24 What parameters are to be considered for testing the accuracy of HUD Input Data Processing and Symbol generation Analogue deflection and video Cathode Ray Tube Installation
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