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COCKPIT DISPLAYS

Prepared for the course Displays and Imaging Sensors (ET-4258)

Submitted by Tarikul Islam

1. Introduction

From the beginning of modern era of civil and military aviation the necessity of integrated

electronic cockpit was recognized. As the mechanical gyroscopic and barometric instrument

panel had limitations to provide sufficient situational awareness and required amount of space

for different displays in cockpit, integrated glass cockpit became obvious. These new displays

exhibit and stimulate aircraft control, autopilot, communication, system monitoring functions,

and navigation. The state of the art display systems which work as Human Machine Interface

(HMI) changed the way pilots aviate their aircraft with improved operational safety margin. In

this paper, the most advanced displays and technologies employed for commercial aviation and

military applications are presented.

2. History of Cockpit Displays

In the mid 1970’s air craft cockpit was crowded by more than hundred instruments and controls.

The primary flight instruments were already congested by indicators, crossbars and symbols.

With the increasing number of elements to provide appropriate situational awareness the cockpit

space was decreasing with dramatic increase in pilot workload. Two Decades with NASA

Langley's 737 Flying Laboratory," Lane Wallace said: "Prior to the 1970s, air transport

operations were not considered sufficiently demanding to require advanced equipment like

electronic flight displays. The increasing complexity of transport aircraft, the advent of digital

systems and the growing air traffic congestion around airports began to change that, however".

Major limiting factor for manufacturing modern display were processing power and availability

of light but effective circuits. As the civil aviation industry was growing rapidly with

accumulating complexity and congestion around terminal areas the need for advanced and

integrated cockpit display became obvious. In figure-1 we see ever growing trend of

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consumption of airline travel as measured by Revenue Passenger Miles (RPM) and capacity

grew at a similar pace billion Available Seat Miles (ASM).

Figure-1: Air travel capacity and consumption in US from 1968 to 2005.

National Aeronautics and Space Administration (NASA) conducted a research for integrated but

easily understood picture of flight situation which resulted in LED (Light Emitting Diode) glass

cockpit display. NASA led glass cockpit display acquired total acceptance for electronic flight

displays and the first glass cockpit became available in 1979. As the situational awareness (level-

1 to level-2/level3) of aircraft’s state relative to its environment improved, safety and efficiency

of the flights improved greatly and the first glass cockpit was used in Boeing 767 in 1982

(figure-2).

Figure-2: Pioneering two crew flight deck of Boeing 757/767. The display screens

inspired the name ‘glass cockpit’.

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Primitive LCD panels were unusable for civil aviation due to their poor resolution with viewing

angle and response time. During late 1990s LCDs were replacing conventional cockpit displays

as their efficiency, reliability and legibility increased greatly. Now a days Modern aircraft such

as the Boeing 737 Next Generation, 777, 717, 747-400ER, 767-400ER, 747-8, and 787, Airbus

A320 family (later versions), A330 (later versions), A340-500/600, A340-300 (later versions),

A380 and A350 are fitted with glass cockpits consisting of LCD units. With the substantial

advancement in microelectronics glass cockpit has become fundamental display system for

airliners, military aircrafts, and business jets. Even state of the art avionics systems like Synthetic

Vision System (SVS), space shuttle (figure-3), integrated Conflict Detection and Resolution

relied on glass cockpits. The better automation capability and integration of controls enable this

cockpit to more accurate display of GPS navigation, Ground Proximity Warning Systems

(GPWS/EGPWS), TCAS (Traffic detection and Collision Avoidance System), weather

information, and NexGen complex conflict geometry & maneuver suggestions.

Figure-3: NASA's fourth space-rated space shuttle, OV-104 "Atlantis" glass cockpit.

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3. Conventional Cockpit

Conventional cockpits use traditional mechanical instruments for

1. Airspeed Indicator (Pitot Static)

2. Attitude (yaw) Indicator (Gyro)

3. Altimeter (Pitot Static)

4. Vertical Speed Indicator (Pitot Static)

5. Heading Indicator (Gyro)

6. Turn Coordinator (Gyro)

Figure-4 represents corresponding positions and displays of basic six.

Figure-4: Conventional cockpit display showing ‘basic six’ of air craft avionics system.

Gyroscopic instrument is used as a Turn Coordinator which works off the principle of

precession. The gyro is mounted in a gimbal with the gyros rotational axis in-line with the lateral

pitch axis of the aircraft and the gimbal with limited freedom around the longitudinal (roll) axis

of the aircraft. With the orientation of aircraft a torque force is developed around the vertical axis

of the gyro and due to precession the torque force moves ninety degrees in the direction the gyro

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is spinning. This torque force and spring will reach equilibrium and the angle that the gimbal and

gyro relax at displayed to the needle which depicts rate of turn (turn coordinator). The figure-5

depicts operating principle of gyroscope.

Figure-5: Mechanical Gyroscopic turn indicator.

Altimeter used to measure aircraft’s altitude above a fixed level. Altitude can be

expressed as a function of pressure as the pressure decreases with altitude. When a barometer is

supplied with a nonlinear calibration so as to indicate altitude, the instrument is called a pressure

altimeter or barometric altimeter. The calibration function of an altimeter is,

Where, c = constant, T = absolute temperature, P = pressure at altitude Z, P0 = Pressure at sea

level. Constant c depends on the acceleration of gravity and the molar mass of the air. The

aircraft barometer measures atmospheric pressure from a static port outside the aircraft. The

altimeter is calibrated to directly indicate altitude above mean sea level in accordance with a

model ‘International Standard Atmosphere (ISA)’.

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Figure-6: Schematic of an aircraft drum type altimeter.

The pilot Pitot tube is to measure the dynamic pressure due to the forward motion of the

airplane through the air, and Static Vents to measure the static, outside barometric pressure as the

airplane gains or losses altitude. Pitot tube feeds three basic flight instruments Airspeed Indicator

(ASI), Altimeter, and Vertical Speed Indicator.

Figure-7: Air Speed Indicator connection with pitot tube.

Speed of the aircraft (Airspeed Indicator) through the air is calculated by measuring

pressure difference between static pressure through one or multiple static ports and stagnation

pressure generated by “ram air” passing through the pitot tube which is generally placed at a

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location chosen to detect the prevailing atmospheric pressure as accurately as possible. This

pressure difference is called impact pressure then fed to ASI to display air speed which is also a

measure of speed at which air is flowing over aircraft. Formation of ice inside or top of air hole

of the pitot tube may cause serious measurement error specially when temperature is below

freezing level and visible moisture in the atmosphere. To compensate this effect electrically

heated pitot tubes are used to prevent ice formation.

Figure-8: Mechanical display of Air Speed Indicator.

The Attitude Indicator (AI) depicts artificial horizon or the gyro horizon and

corresponding position relative to the horizon. As can be seen from figure-9, when the aircraft is

aligned with the artificial horizon it is in level flight. In the same way attitude indicator can be

representative for climb and descent flight. As the airplane maneuver the pair of wings will show

pitch and bank angle. AI is a gyroscopic instrument whose working principle was discussed at

the beginning of this section.

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Figure-9: Cessna 172 attitude Indicator.

Vertical Speed Indicator (VSI) is a pitot tube (static) instrument which measures rate of

climb and rate of descent. The static air pressure system detects altitude changes with change in

barometric pressure and this change is extrapolated to measure the aircraft’s change in altitude

and rate of change. Pilot has the option to monitor both of the observations from altimeter and

VSI. The VSI is in a sealed case connected to the static line through a calibrated leak (restricted

diffuser). Inside the case, a diaphragm attached to the pointer by a system of linkages is vented to

the static line without restrictions. As the aircraft climbs, the diaphragm contracts and the

pressure drops faster than the case pressure can escape through the restrictor, resulting in climb

indications; the reverse is true during descent. If level flight is resumed, pressure equalizes in the

case and diaphragm within six to nine seconds and the pointer returns to zero rate of climb. The

vertical speed indicator has 100-ft calibrations with numbers every 500 ft. Although the vertical-

speed indicator operates from the static pressure source, it is a differential pressure instrument.

The differential pressure is established between the instantaneous static pressure in the

diaphragm and the trapped static pressure within the case (figure-10).

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Figure-10: Vertical Speed Indicator instrumentation.

Heading Indicator is a gyroscopic instrument which replaced magnetic compass because

compass only accurately works when air plane is in level flight with zero acceleration. In the

figure-11 gyroscope is rotated by flow of air mass produced by the vacuum pump, remains rigid

in space as the aircraft turns around its vertical axis. The spinning wheel will resist any change in

position. This is the advantage of HI. When airplane is turning the gyroscope will resist moving

with the turn. The power used to resist turn instead of moving the compass card which will

indicate the heading of the airplane. All the modern aircraft has this gyroscopic element because

they are not affected by magnetic disturbances or have turning errors inherent to the compass.

Figure-11: Heading Indicator operating principle and display.

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In conventional cockpit displays dedicated instruments with specific functionality directly

connected to the corresponding sensors. Separate keys and switches are used to operate to which

direct permanently defined unambiguous functions are assigned. Each display devise is

connected directly to its sensor on a point-to-point basis. As a result pilot continuously has to

process a large volume of simultaneous information displayed at six-pack. Due to human limit of

efficiently and accurately processing multiple simultaneous data sets the number of displays

needed to be reduced. Moreover, display commands needed to be adjusted in accordance with

the flight situation and conflict geometry which tell the necessity of increased automated cockpit.

An automated cockpit consists of ‘multifunction keyboards’, ‘bus systems’, and ‘glass cockpit’.

4. Glass Cockpit

In computer technology, the need for enhancement of situational awareness in more complex

environments, and the rapid growth of commercial air transportation, together with continued

military competitiveness, led to increased levels of integration in the cockpit. The

implementation of Cathode Ray Tubes (CRT) and Liquid Crystal Displays (LCD) greatly

improved the integration and representation of multiple sensor data on a single display. The

information is displayed same way as the old instruments but major difference is electronically

presented information. Glass cockpits enable to display basic-six elements along with exhibiting

other 3D surrounding environment (e.g. Enhanced Ground Proximity Warning Systems, Conflict

geometry) for increasing situational awareness. Before glass cockpits, pilots played a huge role

in the flying of the aircraft, they had to calculate his fuel consumption rate, see how much fuel

was going to last them how far, where they were on the map, when they had to turn. However,

with a glass cockpit, it is as simple as looking at the screen, touching the fuel statistics tab (the

computer responds to the touch screen) and reading off its data. The elements of modern cockpit

displays will be discussed in the following sub-sections.

4.1 Mode Control Panel

The MCP is the primary interface for the pilot for controlling the Auto Throttles (AT) and Auto

Pilot (AP) functions of the Autopilot Flight Director System (AFDS). The Mode Control Panel,

usually a long narrow panel located centrally in front of the pilot, may be used to control

Heading (HDG), Speed (SPD), Altitude (ALT), Vertical Speed (VS), Vertical Navigation

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(VNAV) and Lateral Navigation (LNAV). It is located in the center of the Glareshield for access

by both pilots. It presents the pilot with a visual representation of the AP and AT configuration

through a series of LED displays and switches. The MCP allows the pilot to input commands

that control two Flight Control Computers (FCC). Each computer is named A and B, hence the A

and B on the MCP . When the AP is engaged it sends commands to the aircraft pitch and roll

servos to operate the aircraft flight control surfaces. Also, when the FD switch is armed, the

same commands are sent to the FD display to indicate the pitch and roll profile of the aircraft to

the pilots. The AT system is also a component of the AFDS and can take it's commands from

the MCP and/or the FMC which provides the AT system with commands for N1 limits and target

airspeeds.

Figure-12: A typical example of MCP.

4.2 Primary Flight Display

Since the 1980s most airliners as well as business jets along with increasing number of

newer general aviation aircrafts have glass cockpits equipped with primary flight and multi-

function displays. The PFD provides increased situational awareness by replacing the traditional

six-pack of instruments in the pilots’ panel with an easy to scan display that provides a large

horizon, attitude, altitude, air speed, vertical speed, navigation, communication, terrain,

lightning, and traffic information. An air data computer is responsible for processing the

calibrated airspeed, attitude, altitude, and Mach number from input sensor data (i.e. pitot-static,

gyroscopes, GPS, accelerometers). Then the information is displayed to the pilot over a

LCD/CRT display device.

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Figure-13: A Cessna NavIII PFD showing default flight information.

The most advanced PFD represents integrated 3D real time terrain images with basic display

information. In figure-14, Honeywell’s Synthetic Vision Primary Flight Display (SV-PFD)

presents most advanced integrated PFD which will be offered on multiple platforms for business

jets. It uses Enhanced Ground Proximity Warning System (EGPWS) database and advanced

Head-Up-Display (HUD) symbology. Combined they provide pilots coherent and continuous

situational awareness regardless of weather or time of the day.

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Figure-14: Honeywell’s SV-PFD showing 3D terrain images.

4.3 Navigation Display The Navigation Display provides lateral situation of the aircraft. Advance ND can produce a graphical presentation of the waypoints selected as on the flight management system control display unit. Additionally the pilot may modify or create a new route by movement of a cursor on the display. Improved situational awareness can be achieved by presenting compass, map, flight plan, and terrain data on easy to read format.

Figure-15: ND with integrated terrain and compass images.

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4.4 EICAS/ECAM

Engine Indicating and Crew Alerting System (EICAS) is an integrated system used in modern

aircraft to provide aircraft crew with aircraft engines and other systems instrumentation and crew

annunciations. ECAM system (Electronic Centralised Aircraft Monitoring) was introduced by

Airbus, whereas EICAS (Engine Indicating and crew Alerting System) was originated by Boeing

though they have almost similar functional characteristics. EICAS/ECAM system monitors

aircraft functions and relays them to the pilots. Airbus developed ECAM which not only notify

pilots about the relevant failure but also corrective actions needed to overcome the failure and

system limitations after the failure. Engine operating data is displayed on its CRT units as a

result eliminates the drawbacks of conventional instruments. In the event of any kind of

malfunctioning automatic color coded messages are displayed to the flight crew appropriate to

the degree of probable fatality (i.e. red: urgent). EICAS/ECAM typically includes

instrumentation of various engine parameters, including for example RPMs, temperature values,

fuel flow and quantity, oil pressure etc. EICAS/ECAM is the major element for glass cockpit

system as it replaces all analog gages with software driven electronic displays and at least one

display is set aside for EICAS/ECAM.

Figure-16: Primary EICAS of Boeing 787.

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4.5 Flight Management System (FMS) The modern FMS was introduced on the Boeing 767 but with development and as time

progressed FMS installed even in the very smaller aircraft like Cessna 172. A Flight

Management System (FMS) consists of two major units, a computer unit and a Control Display

Unit (CDU). The basic functionality of FMS is to guide the aircraft through the desired trajectory

by using data from different position sensors (GPS, INS, VOR, DME, NDB etc.). In the cockpit

the CDU provides the primary human machine interface for data entry and information display

which incorporates a small screen and keyboard or touchscreen. In general the same FMS flight

information is displayed on Electronic Flight Instrument System (EFIS), Navigation display

(ND), or Multifunction Display (MD).

Figure-17: Honeywell’s CD-820 the latest control display unit (CDU).

4.6 Multi-Function Display (MFD)

MFD is a six inches CRT or LCD display surrounded by multiple key pads that can be used to

represent desired information in numerous configurable ways. MFDs are used to display

navigation route, moving map, weather radar, NEXRAD, GPWS, TCAS and airport information

on the same flat panel screen. Going even further, MFDs today also can serve to display engine-

operation information and Doppler weather radar images without onboard weather radar. The

high-resolution graphics processed from ground-based radar and relayed via a data-link network

terrestrial-based or satellite-based. When an MFD is integrated with an electronic primary flight

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display (PFD), a full glass panel is obtained with all the required information for pilot (figure-

18). The figure depicts PFD, ND, and GPWS are integrated over same LCD screen which is one

of the most advanced displays that can be found at current time.

Figure-18: Aspen Avionics' EFD1000 multi-function display.

5. ADVANCED DISPLAY TECHNOLOGY

The earlier generation of glass cockpits used Cathode Ray Tube (CRT) which replaced the old

fashioned steam gauges. But due to CRT’s technical and physical limitations Airlines were

searching for more advanced display technology. LCDs (Liquid Crystal Display) came up with

efficient and reliable solution when the emerging goals for airline industries were to improve

situational awareness and decrease pilot workload. The most relevant display technologies will

be briefly discussed in this section.

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5.a Cathode Ray Tube (CRT)

In the late 1960s and early 1970s, the military sought to de-clutter its cockpits by using small

cathode ray tubes (CRT) to replace the mechanical gauges and combine the functions of several

instruments onto a computer-generated screen. This was the genesis of the glass cockpit -

centering initially on the Primary Flight Display (PFD). The operating principle of CRT is

briefly discussed below.

CRTs receive their picture data from ARINC Bus system. The data set is composed of one word

and consists of either Binary(BNR), Binary Coded Decimal (BCD), or Alphanumeric data

encoded per ISO Alphabet. The transfer of graphic text and symbols are used for CRT maps and

other displays. The signal is then decoded by the display controller which processes the internal

components’ signals of the monitor.

Figure-19: A conventional CRT display monitor.

At the back of the monitor the electron gun is placed which fires electrons towards the front

through a vacuum which exists in the tube of the monitor. The gun works like a cathode, hence

the fired rays are called cathode rays. These rays correspond to red, green, and blue channels of

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the display and video card. At the neck of the monitor is an anode, which is magnetized

according to signal processing in the display controller. During propagation through anode the

electrons are pushed or pulled by the characteristic of magnetic anode which controls electrons

towards the correct part of the screen. When the electrons pass through the mesh they hit the

phosphor coating of inside glass screen and lit up. As a consequence light shines through the

front of the monitor and viewing the processed information.

Three differently colored phosphors for each pixel also known as phosphor triads, and depending

on which phosphor the electron hits, that's which color the pixel will light up.

Figure-20: Mig-29 CRT cockpit (left) and NASA’s space shuttle CRT cockpit.

Though CRT displays have greater advantage over mechanical gauges, however the amount of

light in the cockpit and viewing angle seriously diminish visibility of displays.

5.b Liquid Crystal Displays (LCD)

Due to much longer operational time and much less energy requirement, LCDs have been

replacing all other forms of displays in cockpit even CRTs. Primitive LCDs had poor brightness

and limited viewing angles, but advances in display microelectronics enabled LCDs more

sophisticated and efficient. Data processing of the system are in the control/display computer

that takes all of the sensor, condition and flight information and converts that digitally through

the symbol generator, then passes the info to the display through the data bus.

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Active Matrix Liquid Crystal Display (AMLCD) has become the preferred flight instrument

technology in avionics multifunction display application. Now a days, ARINC D 6.7 x 6.7 inch

active display area color MFDs are standard instrument in all Boeing civil air jets. Commercial

AMLCD technology has now produced monitors at 1280 x 1024 resolution (1.3 megapixels) in

sizes of 16 to 21 inches in diagonal.

Figure-21: Boeing 777 sunlight readable AMLCD display.

The latest AMLCDs have performance parameter and capabilities that exceed those of CRTs.

The main advantages are in weight, power, volume (size), and reliability. However, the AMLCD

performance exceeds that of CRTs in other areas such as:

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The CRT has an inherent wider viewing angle and wider operating temperature range than does

the AMLCD, but the AMLCD meets the needs of aviation. Though LCDs are far more expensive

than CRTs, but due to its’ longer life span they are worth of the price.

Liquid crystals are intermediate phase between crystalline solids and isotropic liquids but

exhibit properties of both. Though several types of liquid crystals (LC) exist each having their

own properties but liquid crystals in a nematic phase, in which there is no spatial ordering of the

molecules, for example, are used in LCD technology. At lower temperature LC remains in its

solid state and becomes liquid with increasing temperature while retaining some of their

crystalline properties. As a matter of fact the material is only called a LC when they are in

mesophase (figure-22). LCDs display mechanism lies on the special properties of these liquid

crystals and light.

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Figure-22: Solid, LC, and liquid crystals.

The anisotropic properties of LCs make it sensitive to varying refractive index and dielectric

constant which enable electric field to realign LCs to work as controller for polarization of light.

This procedure is called Freedericksz transition and used in LCDs. The two conventional LC

operating modes will be discussed below.

Twisted Nematic Mode: The TN mode employs the rotation of polarization axis of the linear

polarized light. The system consists of a layer of LCs enclosed between two glass plates. The

transparent electrodes at the inner surface work to patterned to form the desired visual image.

Due to these surfaces’ polished polymer coating the LCs over two surfaces lies perpendicular to

each other. Across the film of liquid crystal a ninety degree twist is formed by the molecules. In

the off state when linear polarized light is travelling through first polarizer the light rotates along

the crystals and go into second molecular layer as a result the light will twist ninety degrees as

well. When the power is on to energize the cell, LCs are influenced by the electric field, hence

light transmitted through first polarizer will be blocked by the second polarizer which forms the

dark image. Detail of the TN mode is shown in figure-23.

Figure-23: TN mode showing the OFF state (left), and an ON state with voltage applied (right).

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Super Twisted Nematic Mode: Better image quality is obtained by using this mode which

incorporate faster change in realignment of molecules. In this case the twist is greater than ninety

degrees and below 270o. The liquid crystals at the surface are placed at some angle rather than

90o. As a result, it doesn’t work on the light guiding principle as of TN but instead birefringence

principle. Color in the off state is resulted from the birefringence, cell thickness, and position of

the polarizers. Liquid Crystals in the cells are super twisted which facilitate to use a high

multiplex rate. For increasing twist the molecules in the middle try to align with the applied

electric field which gives rise to very steep transmission-voltage curve allowing 240 line

multiplexing.

Figure-24: Super TN mode showing the OFF state (left), and an ON state.

Active Matrix Liquid Crystal (AMLCD): As most of the displays of cockpits are AMLCDs,

the working principle will be discussed here. An array of thin film transistors (TFT) work as

controller for AMLCD each using a capacitor activates single pixel. TFT uses deposited layers of

materials to establish semiconductor, insulators, and electrodes. The electrodes are placed as gate

lines (row) and addressing lines (column). One row of the matrix is activated at a time. The

capacitor is charged up-to a desired value provided by the column voltage resulting in desired

transmission change through the LC element. During charging the transistors are switched off

and pixel capacitor provides a standby voltage to the LC element. Now next row can be selected

by gate line while other rows are kept isolated to reduce cross talk. When all the rows have gone

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through same procedure the entire display is reconstructed. Such refreshing prevents fading out

of the picture which would otherwise happen as charge gradually leaks from the pixel capacitors,

reducing their voltages and thus changing the light transmission states of the pixels.

Figure-25: Elements of AMLCD depicting electrodes and color filters.

6. Head Up Display (HUD)

The HUD provides guidance to the pilot displaying necessary flight information represented over

a transparent screen which does not require changing the usual view point of pilot. As a result

pilot can see information with head positioned up and looking forward. The guidance

information includes air data, navigation, flight guidance, and airspeed. A modern HUD is

shown in figure-26. HUD was introduced in military aircrafts, but when the benefit was

recognized it explored commercial aviation industry along with automobiles.

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Figure-26: Transparent HUD screen illuminated by necessary flight information.

HUD consists of three components: projector, combiner, and a computer. In the second

generation of HUD, the projector uses a solid state light source (e.g. LED) which is modulated

by an LCD screen to display an image. The combiner is a glass placed in from of the pilot which

displays holographic image generated by the projector. The special coating of combiner reflect

the monochromatic light from projector at specific wavelength when allows to pass all other

frequencies of the visible spectrum. The video generating computer processes the flight

information to be displayed and generates imagery and symbology.

Figure-27: Typical HUD architecture showing CRT projector and combiner.

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7. Military Cockpit Displays

With the emerging display technology the military cockpits followed the same trend as

commercial air jets. Instrument panels are wholly replaced by electronic Multi Function Displays

(MFD) and multi-function re-configurable control keys. Controls are incorporated onto the stick

and throttle to enable the pilot to maintain a head-up and eyes-out position – the so-called Hands

On Throttle And Stick or HOTAS concept. These controls may be then further augmented by

new control media such as head pointing with a Helmet Mounted Sighting System or Direct

Voice Input (DVI). Development in audio visual displays empowered for direct voice output of

aircraft status information and audible warnings. In figure-28, the most sophisticated fighter F-35

cockpit is shown where we can see a large LCD touch screen displaying flight information,

color-coded symbology, pictographs, and digital information. Since, military aviation employs

similar display technology and performance requirements as discussed previously for civil

application, only Head Mounted Display will be presented in this section.

Figure-28: Integrated Color AMLCD assemblies for U.S. Army's F-35 fighter.

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7.a Helmet Mounted Display (HMD): In the mid seventies very ordinary HMD was introduced

for experimental purpose to assist pointing heat seeking missiles. South African Air Force was

the pioneer to develop and to fly with helmet mounted sight. The main purpose of HMD is to

obtain better situational awareness and targeting weapon system where pilots head is pointing.

The position measuring system inside helmet must be capable of measuring the elevation,

azimuth, and tilt of the pilots head relative to the airframe which assumes that helmet boresight is

the target direction to which missiles should be aimed. Earlier HMDs utilized compact pencil

shaped CRTs embedded in the helmet and suitable lenses to focus the CRT image on the pilots

visor focused at infinity. At present time, like HUD most of the helmet displays are employing

LCDs with LED illuminators to create image in helmet. The most recent development is to

display color symbols and videos. For future fighter cockpits research is being conducted to

measure movement of eye to detect where the pilot is looking. Another future technology to

come into scene is Direct Retinal Projection which directly illuminates information on pilot’s

retina generated by a low powered laser. Figure-29 shows helmet mounted display system for

F-35 Fighter which was designed to provide pilots with binocular-wide field-of-view, give night

vision abilities and scare enemy pilots at first sight. It enabled F-35 to become first combat plane

without HUD. The helmet was developed by Vision Systems International

Figure-29: Helmet Mounted Display for F-35 Lightning II Joint Strike Fighter.

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8. Future Cockpit Displays

Though cockpit displays have very short time of history but it came through substantial

improvement from mechanical gauges to modern integrated electronic displays. Now a days 14

inches models of LCD display panels are common in commercial cockpits. In the future, cockpit

displays will be bigger, lighter, and less power hungry. As an example, Thales is trying to

produce single screen cockpit which will integrate all the necessary flight data that can be

tailored to what the crew wants to see. The area of artificial intelligence for cockpit automation is

one which requires further research. The goal is to develop techniques to monitor and assist the

operator rather than to replace him/her and to anticipate future problems rather than giving a

warning once a fault or error has occurred. Moreover, state of the art 3D displays will be able to

show realtime identical 3D images of terrain, traffic, and navigation information. By 2020 all of

the civil aviation aircrafts will have ADSB (Automatic Dependent Surveillance Broadcast)

System which will operate under “free flight” concept and displays will be capable of depicting

ADSB traffic. Properly designed expert systems will offer capabilities for safety and efficiency

unmatched by today's systems.

9. Conclusion

Modern displays simplified whole instrument panel to a few LCD screens which not only

reduced pilot workload but also increased number of operable aircrafts in the same airspace at

the same time by increasing certainty and assisting narrowing down the separation requirement

between aircrafts. As the air space is becoming more crowded day by day, more advanced

integrated cockpit becoming available like the Thales’ single screen glass cockpit. Few

drawbacks of these displays are notified, for example more expensive than conventional

instrument panel, vulnerable to electrical failures which may lead to unavailability of all the

integrated information over that display, it may occupy excessively pilot’s attention right into the

displays, and obviously training is needed for the pilots to achieve sufficient skill to operate

them. However, the advantages of modern cockpit displays are so superior that at present

aviation industry almost all the aircrafts have been taking the benefit of having LCD panels in

front of their driving seats.

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