Parts of an aeroplane:-
In the early days of aviation, the fuselage was merely an open structural
mount 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-wir6" fuselages that not only increased lift and decreased drag,
but also provided protection for pilot and passenger, as well as space
for cargo. This type of structure, known as truss, was gradually superseded
by the monocoque (literally, single shell) fuselage. The loads imposed
on such a structure are carried primarily by the skin, rather than by the
internal framework, as in the trussed structure. In varying stages of advanced
design, it is the most common fuselage presently in use.
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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, but the monoplane was subject to less 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 structural elements inside the skin. In present-day aircraft, cantilever construction is employed in large aircraft, and external bracing is used only for small, light planes.
The structure of a typical wing consists of a spar-and-rib framework enclosed by a thin covering of metal sheet, of treated fabric, or, infrequently, of bonded plywood or of resin-impregnated glass fibre. The spar, or beam, extends from the fuselage to the wing tip. One or more spars may be used in the wing, but the single spar is the preferred design. The ribs, at right angles to the spar, give the wing its external shape. If the covering is of metal sheet, it contributes its own share of strength to the wing. This "stressed skin" type of wing is currently used in all large planes; fabric covering is employed for the wings of some small craft.
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 knifelike leading edge. Such streamlining helps to reduce the shock
of compressionwhen 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. For speeds beyond the sound barrier, the non-tapered
wing is often the most efficient.
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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 stabiliser,
and the rear movable section, as the elevator. 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,
but in supersonic flight the tail should be as small as possible. Its complete
elimination would be the ideal design.
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Present-day landing gear is one of the most intricate of all aeronautical
mechanisms. Its components include the oleo strut, a hydraulic arm connecting
the wheel with the wing or fuselage, absorbing the shock of landing; the
retracting mechanism, which raises and lowers the gear; the wheels; and
the wheel brakes. A number of types of undercarriage are known, but two
are most commonly employed: the conventional two-wheel gear and the tricycle
gear. 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 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 maneuvering are improved and
the danger of nosing over is diminished. 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.
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Components of modem aircraft necessary for flight control include devices
manipulated from the cockpit by the stick or wheel, and instruments which
provide the pilot with essential information.
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The attitude of an aeroplane (its orientation relative to the horizon and to the direction of motion) is determined by three control devices, each of which provides for movement about a different axis. The three 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 airlines, and the wheel, with its greater leverage, is generally used in larger airlines, as well as in some small ones.combustion engine or a turboprop engine is utilized to drive the propeller that thrusts the air backwards by having airfoil-shaped blade sections cutting through the air in a screw-like fashion. In jet propulsion, the forward thrust is provided by the discharge of high-speed gases through a rear-facing nozzle.
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 economic consideration, 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
minimising the drag caused by the engine.
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The internal-combustion engine used in most propeller-driven aircraft is one of two types, the reciprocating engine and the compound engine. In the reciprocating engine, heat energy is utilised 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 gasoline operated. In general, the advantages of the reciprocating engine are reliability and fuel economy.
The compound engine consists of a reciprocating engine combined with
an exhaust gas 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 reciprocating engine is its high-power capacity
at high altitudes. The compound engine served as the chief engine in US
military aircraft during World War 11, before the advent of jet propulsion.
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Like the ramjet, the rocket engine has its chief application in guided Missiles. A solid propellant rocket, rocket-assisted takeoff (RATO), is used for supplementary initial power in the takeoff of heavily loaded aircraft.