Optsub Att General 17 Aeroplane Project Aero

8/8/2019 Optsub Att General 17 Aeroplane Project Aero

1/33


2/33

An aeroplane can lift itself because the wing, angled slightly downwards

towards the back, pushes air downwards as the wing is propelled forwards by

the engine. In reaction, the wing is pushed upwards, generating lift, as

predicted in the third law of motion formulated by Isaac Newton: that for

every action, there is an equal and opposite reaction. The magnitude of the liftthat is generated depends upon the shape of the aerofoil in cross-section, the

area and shape of the lifting surface, its inclination relative to the airflow, and

the airflow speed.

Lift

The lift developed on a wing or similar surface is directly proportional to the

plan area exposed to the airflow but proportional to the square of the speed ofthe airflow. It is also approximately proportional to the inclination, or angle of

attack, of the aerofoil relative to the airflow

for angles typically in the range of plus and minus 14. At greater angles the

airflow characteristics change rapidly, the


3/33

flow breaks away, and lift falls drastically. In these circumstances the

aerofoil is said to have stalled.

As an aeroplane flies on a level course, the lift contributed by the wing

and other parts of the structure counterbalances the weight of the plane.Within limits, if the angle of attack is increased while the speed remains

constant, the plane will rise. If the angle of attack is decreased, that is,

the wing is inclined downward, the plane will lose lift and start to

descend. An aeroplane will also climb from level flight if its speed is

increased, and it will dive if its speed is decreased.

During the course of a flight, a pilot frequently alters the speed and angle

of attack of the aircraft. These two factors are often balanced against

each other. For instance, if the pilot wishes to increase speed and yet

maintain level flight, the angle of attack must be decreased to offset the

extra lift that is provided by the increase in the speed of the aircraft.


4/33

In preparing to land, the pilot must ease the plane down and at the same

time reduce its speed as much as possible. To compensate for the

considerable loss of lift resulting from the decrease in speed, the pilot

provides additional lift by altering the wing area, effective curvature, and

angle of attack. This is done through the use of high-lift devices called flaps,large wing extensions located at the rear or trailing edge. Most flaps are

normally retracted into the wing during cruising flight. If extra lift is

wanted, the pilot extends the flaps outward and downward. Sometimes

high-lift devices are provided at the front, or leading, edge of a wing.

Drag

Factors that contribute to lift in flight also contribute to undesirable forces

called drag. Drag is the force that tends to retard the motion of the plane

through the air. Some drag is a result of the resistance of the air to objects

moving in it and is dependent upon the shape and smoothness of the surface. It

can be reduced by streamlining the aircraft. Some designs also incorporate

devices to reduce the drag owing to friction by maintaining the surface airflow

in so-called laminar form.


5/33

Another form of drag, however, known as induced drag, is a direct result of the lift

produced by the wing. Work has to be done to produce lift and the induced drag is

the measure of this. The expenditure of energy appears in the form of eddies, or

vortices, which form along the trailing edge and especially at the outer extremities,or tips, of the wing.

Aeroplane designers conceive aircraft with the highest possible ratio of lift to drag,

which occurs when the drag resulting from the shape is equal to the induced drag

resulting from the lift. The lift-to-drag ratio is limited by factors such as speed and

acceptable weight of the airframe. A subsonic transport aircraft may have a lift-to-

drag ratio of about 20, while that of a high-performance sailplane may be twice this.On the other hand, the extra drag that occurs when an aircraft flies at supersonic

speed reduces the achieved lift-to-drag ratio to less than 10.


6/33

Aeroplane, heavier-than-air craft that is usually propelled mechanically and

supported by the aerodynamic action of the airstream on fixed-wing surfaces.

Other types of aircraft that are heavier than air include the glider or sailplane,

which is similarly equipped with fixed-wing surfaces but is not self-propelled, and

rotary-wing aircraft, which are mechanically driven and supported by overhead

rotors, such as the Autogiro and Helicopters. Another type is the ornithopter,which is lifted and propelled by flapping wings. Toy-sized ornithopters have been

developed, but large-scale experiments have been unsuccessful. For the history of

heavier-than-air craft, see Aviation

The term aeroplane generally denotes craft operated from land bases, but it

applies also to several other categories of aircraft, including the carrier-based

plane, the seaplane, and the amphibian. The principal variation in

configuration can be found in the landing apparatus.


7/33

The carrier-based plane is a type of land plane designed for use on an

aircraft carrier, and is fitted with a tail hook that engages a cable stretched

across the deck to arrest the plane after landing. The seaplane employs floats

instead of the wheel gear of the land plane. In the variety of seaplane known

as the flying boat, the fuselage is constructed as a hull, similar to that of a

seagoing vessel, and serves to keep the plane buoyant. The amphibian isequipped with both wheel gear and hull or floats to permit operation with

equal effectiveness on land and water.

Before World War II, flying boats were used for military transports and

for intercontinental commercial service. These planes were limited to

low flying speeds and to low landing speeds in water. With the advent of

planes that fly and land much faster, to gain efficiency, large planes have

been limited to land-based operation. The amphibian, even slower

because of its double undercarriage, is less commonly employed than the

land plane. For light sports planes,


8/33

amphibious floats are available. Generally resembling conventional floats, they

have a recessed wheel located at the centre. The wheel does not extend far

enough to add much drag to the float in the water, but it protrudes far enough

to enable wheeled landings to be made on hard-surfaced runways or short-cut

grass.

Particular types of heavier-than-air craft include the VTOL (vertical take-off

and landing) and STOL (short take-off and landing) craft, and the

convertiplane. The VTOL craft is an aeroplane that can rise vertically, move off

horizontally, and then reverse the procedure for a landing. The term VTOL

is limited to describing aircraft with performance similar to that of

conventional aeroplanes but with additional vertical take-off and landing

ability. Several means are used to lift VTOL aircraft off the ground. The directdownward thrust of jet engines is used in several designs, but the power

required is high. Rotating wings and ducted fans are also


9/33

used for direct lift, but they introduce drag into the horizontal flight.

Convertiplanes, combining the rotors of helicopters with the fixed

wings of aeroplanes, show promise for short-distance commercial

VTOL operation. They compete directly with helicopters, but can fly

faster.

The STOL craft is an aeroplane that takes off and lands very steeply,

thus requiring only a short runway. For a given payload, it is more

efficient in terms of fuel consumption and power requirements than a

VTOL craft. It is also capable of higher speeds and longer-range

flights than a helicopter. In September 1999 a solar-powered aircraft

completed its first test-flight in California. The aircraft has awingspan of 75 m (247 ft) and flies without a pilot. In the future it is

thought the plane could remain in continuous flight for up to six

months at a time and would be employed for scientific tests and

telecommunications projects. For lighter-than-air craft, see Airship;

Balloon


10/33

The present-day conventional aeroplane may be divided into four

components: fuselage, wings, tail assembly, and landing gear, or

undercarriage.

A Fuselage

In the early days of aviation, the fuselage was merely an open framework to

support the other components of the plane; the bottom of the airframe served

as the landing gear. Subsequently, the need for greater strength and better

performance resulted in the development of enclosed, box-like strut-and-

wire fuselages that decreased drag, and also provided protection for pilot

and passenger, as well as space for the payload. This truss structure wasgradually superseded by the monocoque (literally, single shell) fuselage. The

loads imposed on such a structure are carried primarily by the skin, rather

than by an internal framework, as in the trussed structure. It is the most

common fuselage presently in use. The outer shell also confers the possibility

of pressurizing the internal volume for high-altitude flight.


11/33

Wings

Assembling an Aeroplane Here, at a McDonnell-Douglas assembly line,

several large passenger planes are in production. In the foreground, the

wing infrastructure is fastened to a body section. Further on in the

assembly line, the tail section and engine mounts are added.Tom

Carroll/Phototake NYC

Although the single-winged plane, known as the monoplane, made its

appearance in the first decade of powered flight, early aeroplane

construction favoured the use of two wings (the biplane), and

occasionally even three or four. Multiple-wing planes have the

advantage of superior lift and relatively stronger construction, but the

monoplane has lower drag. Once the cantilever principle of wing

construction was developed, the dominance of the monoplane was

assured, although it did not become the design of choice until the 1930s.

Cantilever wings obtain their entire strength from internal structural

elements. Cantilever construction is employed in most present-day

aircraft, and external bracing is used only for some small, light planes.


12/33

The structure of a typical wing consists of a spar-and-rib framework enclosed

by a thin covering of metal sheet. Treated fabric, or, infrequently, bonded

plywood or resin-impregnated glass fibre are used for some small aircraft and

sailplanes. The spar, or beam, extends from the fuselage to the wing-tip. One

or more spars may be used in the wing, but the two-spar design is most

common. The ribs, normally at right angles to the spars, give the wing its

external shape. If the covering is of metal sheet, it contributes its own share ofstrength to the wing. This stressed-skin type of wing is used in all large

planes, although there is an increasing use of high-strength reinforced plastic

skins and structure.

The size and shape of wings vary widely, depending on specific aerodynamic

considerations. Wings of many supersonic planes have a high degree of

sweepback (arrowhead tapering from the nose of the plane) and are as thin as

possible, with a knife-like leading edge. Such a shape helps to reduce the

shock of compression when the plane approaches the speed of sound. The

structural importance of the wing is dramatically demonstrated by the

development of the so-called flying wing, a craft in which fuselage and tail

are almost entirely eliminated.


13/33

Tail Assembly

The conventional type of tail assembly consists of two basic surfaces,

horizontal and vertical, each of which has movable sections contributing

to control of the craft and fixed sections to provide stability. The leading

section of the horizontal surface is known as the horizontal stabilizer,

and the rear movable section is known as the elevator. Sometimes thewhole surface can move and the elevator is eliminated. The stationary

section of the vertical surface is called the fin, and the movable section,

the rudder. Two vertical surfaces are used in some aircraft; in that case,

a double rudder is used. The V-shaped tail combines the rudder and

elevator functions in a single device. Tails vary in size according to the

type of aircraft. In some supersonic aircraft the horizontal tail is

replaced by a foreplane, or canard, located near the nose of the plane.

Landing Gear

Present-day landing gear is one of the most intricate of all aeronautical

mechanisms. Its components include the shock strut, a hydraulic leg

connecting the wheel with the wing or fuselage to absorb the shock of

landing; the retracting mechanism, which raises and lowers the gear; the


14/33

wheels; and the wheel brakes. There are a number of types of

undercarriage, but two are most commonly employed: the older two-

wheel gear and the nose or tricycle gear, which is now usual. The

former consists of two large wheels located forward of the centre of

gravity of the plane with a small wheel at the tail. A tricycle gear

consists of two large wheels or wheelgroups behind the centre of gravity

and a third wheel, called the nosewheel, in front of the two main

wheels. Landing is easier with the tricycle gear because braking and

manoeuvring are improved and the danger of nosing over is

diminished. Some large aircraft have more than two rear wheel groups.

Other forms of landing gear include a caterpillar tread for handling

heavy loads on poor landing fields, a swivelling gear for landing in

crosswinds, and a combination ski-wheel gear for use on ice and snow.


15/33


16/33

Components of modern aircraft necessary for flight control include devices

manipulated from the cockpit by the stick or wheel and by the rudder

pedals, and instruments that provide the pilot with essential information.

A Mechanical Controls

Basic Movements of an Aeroplane Bridgeman Art Library, London/New

York

Expand

The attitude of an aeroplane (its orientation relative to the horizon and to

the direction of motion) is conventionally determined by three control

devices, each of which provides for movement about a different axis. Thethree devices include the movable sections of the tail, which are the

elevators and rudders; and the movable sections of the trailing (aft) edge of

the wing, known as ailerons. The control surfaces are operated from the

cockpit by means of a control stick or wheel column and rudder pedals.

Stick control is used in smaller, lighter aeroplanes, and the wheel, with its

greater leverage, is generally used in larger aircraft, as well as in some

small ones


17/33

Elevators provide for pitching movement around the lateral axis. A backward

pull on the control stick or wheel column raises the elevators, thereby

depressing the tail and lifting the nose of the plane for a climb. Forward

movement of the stick or column produces the opposite effect, making the

plane dive.

Ailerons, usually placed far out on the wing, control rolling movement aroundthe longitudinal axis. Leftward movement of the stick or wheel raises the left

aileron and lowers the right, thereby banking the plane to the left. The

reverse tilt occurs when the stick or wheel is moved to the right.

Rudders provide for turning movement around the vertical axis, in

coordination with the ailerons, changing the course of the plane to the left or

right. When the right rudder pedal is pressed, the rudder turns the plane to

the right around the vertical axis. Pressing the left pedal produces a left turn.

To ensure easier and more dependable handling of all control surfaces, a

number of secondary controls have been devised. Trim tabs are used on

rudders, elevators, and ailerons as a means of adjusting the equilibrium,

or trim, of the plane. Other


18/33

secondary controls include flaps (on trailing edges) and slots (on leading

edges) to increase lift for take-off or drag for landing, or to improve various

other flight characteristics. Spoilers are surfaces that normally lie flush with

the wing but can be raised to present a flat surface to the airstream and

spoil the lift of the wing. Somewhat similar surfaces are called air brakes

and extend at right angles to the fuselage or undersurface of the wing to slowthe speed of the plane. The control surfaces may be operated directly by pilot

effort or by a hydraulic or electrical power system. In the latter case the

pilots commands may be transmitted mechanically, by electrical signals

(fly-by-wire) or by optical signals (fly-by-light).

Instruments

Flight Control Panel The cockpit of a Concorde jet shows the complexity of

flight controls. Electronic and computerized equipment in the cockpit

provides information regarding navigation, speed, altitude, landing, and

engine performance.Albert Visage/Explorer/Photo Researchers, Inc.


19/33

Information required in flight is provided by various types of equipment,

which may be divided into four general categories: power-plant

instruments, flight instruments, landing instruments, and navigation aids.

Power-plant instruments indicate whether the engines are functioning

properly and include the tachometer, which shows the revolutions per

minute of each engine, various pressure gauges, temperature indicators,

and the fuel gauges. The primary flight instruments provide indications of

speed (the air-speed indicator), direction (the magnetic compass and the

directional gyro), altitude (the altimeter), and attitude (the rate-of-climb

and turn-and-bank indicators and the artificial horizon). Several of the

flight instruments, including the automatic pilot, utilize the gyroscopic

principle.

Landing instruments needed in poor visibility are of two types, the

instrument-landing system (ILS), providing direct signals to the pilot to

ensure a safe landing, and the ground-controlled approach (GCA), a system

employing radar equipment on the ground to guide the pilot solely by radio-

telephonic advice. The ILS is widely used in civil aviation; the GCA system,

in military aviation. Both systems may also use the standard approach

lighting system (ALS), which guides the aeroplane the last few hundred

metres of the airway route to the runway.


20/33

Flying the Flyer

Orville Wright mans the controls

of the Wright Flyerin 1908, five

years after he made the worlds

first successful, sustained flight.

The Wright brothers experiments

with heavier-than-air flight had

launched Flyer Ion December 17,

1903, near Kill Devil Hill in Kitty

Hawk, North Carolina. The first

flight lasted about 12 seconds, and

the plane travelled 36.5 m (120 ft)

at an altitude of roughly 3 m (9.9ft) and an airspeed of 48 km/h (30

mi/h). Wilbur Wright made a

longer, 59-second flight later on the

same day.


21/33

Ornithopter Design Leonardo da Vinci designed

several flying machines. This one, called an

ornithopter, simulated the motion of a bird flying.

Assembling an Aeroplane Here, at a

McDonnell-Douglas assembly line, several

large passenger planes are in production. Inthe foreground, the wing infrastructure is

fastened to a body section. Further on in the

assembly line, the tail section and engine

mounts are added


22/33

Henson and Stringfellow's "Aerial Steam Carriage" One of the biggest difficulties

faced by early would-be pilots was finding an engine that was both powerful and

light. Many models, such as the Henson and Stringfellows Aerial Steam Carriage

(shown above) might have flown as early as 1845 with adequate engines.

Unfortunately, the only engines available were steam engines, which were too weak

or too heavy for successful flight. It was not until the arrival of the compact,

relatively lightweight petrol engine that planes were able to get off the ground.


23/33

Culver Pictures/Courtesy of Gordon Skene Sound Collection.

All rights reserved.

Amelia Earhart

In 1932 Amelia Earhart became the first woman to make a soloflight across the Atlantic Ocean. In 1937 she and a navigator,

Frederick Noonan, attempted a flight around the world.

Towards the end of their journey they disappeared somewhere

over the central Pacific Ocean; their fate remains a mystery.

Here, Amelia Earhart speaks of the aircrafts rapid

transformation from a novel invention to an ordinary part of

everyday life.


24/33

Precursor to the famous Sopwith Camel fighter of World War I, the

Sopwith Pup was a light, manoeuverable aeroplane. It travelled at speeds

of 185 km/h (115 mph) and was among the first planes to use the new

aileron wing design. Ailerons are hinged flaps on the tips of wings used toturn, or bank, the plane.Dick Hanley/Photo Researchers, Inc.

During the period before World War I the design of both the aeroplane

and its engine showed considerable improvement. Pusher biplanestwo-

winged aeroplanes with the engine and propeller behind the wingwere

succeeded by tractor biplanes, with the propeller in front of the wing.

Only a few types of monoplanes were used.


25/33

Throughout World War II, aircraft became increasingly crucial factors

in military strategy and battles. The need to produce high-performance

military aeroplanes as rapidly as possible during the war served as the

impetus for many advances in aircraft design and production techniques.

Here, World War II military aircraft fly in formation.


26/33

Air power played a significant role in World War II. The vintage Fairey

Swordfish, shown here, contributed to Allied naval victories in 1940 and

1941. This torpedo bomber, although not as advanced as some of the other

bombers in use at the time, crippled an Italian fleet at Taranto and

inflicted severe damage on the German battleship Bismarck.Ian A.

Griffiths/Robert Harding Picture Library

The most significant development of all was jet propulsion. It was

originally proposed by Frank Whittle in Britain. However, it was Germany

that developed and flew the first jet-propelled aircraft, the Heinkel He 178,

powered by an HeS 3B engine developed by Hans von Ohain. The aircraft

first flew in August 1939, just one week before the outbreak of war.


27/33

PROPULSION

Two basic means are used to provide the thrust for an aeroplane in flight:

propellers or jet propulsion. In a propeller-driven aeroplane either a piston-

driven internal-combustion engine or a turboprop engine is utilized to drive the

propeller, which thrusts the air backwards because it has aerofoil-shaped blade

sections cutting through the air in a screw-like fashion. In jet propulsion, theforward thrust is provided by the discharge of high-speed gases through a rear-

facing nozzle. Rocket engines, working on a similar principle, are occasionally

used.

An aircraft engine must satisfy a number of major design requirements, including

high reliability, long life, low weight, low fuel consumption, and low frontal area.

The most important factor is reliability. Long life is mainly an economicconsideration, of special interest in commercial aviation. The relative importance

of the other three requirements depends upon the type of plane that the engine is

intended to propel. Low weight and low fuel consumption are naturally

interdependent because the fuel itself is a weight factor. Low frontal area is

desirable as a means of minimizing the drag caused by the engine.


28/33

Piston Engines

The piston engine used in most propeller-driven aircraft is one of two types,

the reciprocating engine and the rotary engine. In the reciprocating engine,

heat energy is utilized to move pistons operating within cylinders. Cylinder

arrangement is generally in-line, horizontal-opposed, or radial, and either

air-cooling or liquid-cooling systems are used. Nearly all aircraft

reciprocating engines are petrol operated. In general, the advantages of thereciprocating engine are reliability and fuel economy. The rotary engine

replaces the pistons by a single rotating one and hence has fewer ports. It is

claimed to produce lower vibration. Some engines of this type are becoming

available for use in small aircraft.

The compound engine consists of a reciprocating engine combined with an

exhaustgas turbine- that drives a supercharger, an air compressor in the

intake system of the engine. The supercharger compensates for the

decreasing density of the atmosphere at higher altitudes. The chief

advantage of the compound engine over the basic reciprocating engine is its

high power at altitude. The compound engine served as the chief engine in

United States military aircraft during World War II, before the advent of jet

propulsion. British high-performance reciprocating engines of that era used

mechanically driven superchargers.


29/33


30/33

with the oxygen in the air, increasing the gas temperature and volume. The high-

pressure gases are then directed through a turbine, which drives the rotating

assembly of the engine. In the case of the turbojet the expansion is partial and

the residual gas, which is now at intermediate pressure, is accelerated by

expansion through a rear-facing nozzle, to produce a high leaving velocity and,

with it, the desired thrust.

Turboprop and turbofan engines extract most of the gas energy in the turbine,

the residual jet thrust being of secondary magnitude. Turboprop engines are

efficient for medium-sized planes at speeds up to about 480 to 640 km/h (300 to

400 mph). At higher subsonic speeds the turbofan is the preferred engine, as the

performance of a propeller drops to a low level of efficiency. Turbofan engines

use less fuel and are quieter than turbojets, but at higher, supersonic, speeds the

high exhaust velocity of the turbojet is necessary.

The ramjet engine is a jet engine in which the air compression needed for

combustion is obtained from the speed of forward motion alone. As in the

turbojet, its total power output is delivered as the jet thrust of its expelled gases.

Although the ramjet can be applied to piloted aircraft, its present rate of fuel

consumption is so prohibitively high that it is used only in guided-missile

applications.


31/33

The rocket engine carries its own oxidant as well as its fuel and, like the ramjet,

has its chief application in guided missiles. A solid-propellant rocket is used for

rocket-assisted take-off, supplementary initial power for heavily loaded

aircraft.


32/33

Bibiliography

Microsoft Encarta CDs Google Search


33/33

Documents

Optsub Att General 17 Aeroplane Project Aero