In this section, the major parts of a fixed-wing aeroplane are described. There are many different aircraft configurations, as discussed in the next section. For our present purpose, we reference a somewhat standard aircraft configuration, with a single fuselage, a single wing attached to the fuselage, podded engines mounted underneath the wings, and horizontal and vertical tail surfaces mounted to the fuselage, aft of the wing.
This configuration is in wide use today for commercial, military, and general aviation applications. The following discussion is generally applicable to other aircraft configurations, discussed in the next section. The major components of an aeroplane are the fuselage, main wing, empennage, engines, and landing gear.
The fuselage contains the cockpit, passenger, and cargo compartments. The main wing extends from either side of the fuselage and often has integral fuel tanks within it. The empennage4 is the tail area of the aeroplane, comprising the horizontal and vertical stabilizers and the associated moving control surfaces: the elevators and rudders, respectively.
If the aeroplane is a powered aeroplane, there are one or more wing or fuselage-mounted engines. The powerplant may be a reciprocating-engine–propeller combination or a jet engine. The engines may be podded, with the engine pods or nacelles mounted above orbelowthewingsoronthesidesofthefuselage.
The engines may be buried in the fuselage, with an inlet or intake opening towards the front of the fuselage and exhaust openings at the aft end. The landing gear comprises wheels with tyres attached to struts, extending from the fuselage, wings, or engine pods.
Often, the landing gear configuration consists of two main gear assemblies under the wings and a nose gear at the front of the fuselage, although other configurations are possible. The elevators the rudder on the empennage, and the ailerons on the wings comprise the primary flight control system.
Each of these control system surfaces provides an incremental aerodynamic force that creates a moment to rotate the aircraft about its centre of gravity (CG) in the desired direction. these control surfaces enable the rotation of the aeroplane in three dimensions, where the elevator, ailerons, and rudder provide pitch, roll, and yaw rotations, respectively.
Elevators are flap-like devices located at the trailing edges of the horizontal stabilizers. Some aircraft, typically military fighter aircraft, have all-moving horizontal stabilizers, called stabilators or stabs, instead of a combination of stabilizers and elevators. The ailerons on the left and right wings deflect in opposite directions; that is, when the right aileron deflects upward, the left aileron deflects downward and vice versa.
The downward deflected aileron results in additional lift on one side of the wing, while the upward deflected aileron results in decreased lift on the other side of the wing, creating the rolling moment. The additional lift produced by the downward deflected aileron also results in additional drag.
This additional drag produces a yawing moment in a direction opposite or adverse to the desired direction of the roll and therefore is called adverse yaw. To counter this adverse yaw, the rudder is deflected to produce an opposing yawing moment, resulting in what is termed a coordinated turn. High-speed aircraft also have secondary or auxiliary flight controls, which include devices on the wings called flaps, slats, and spoilers.
Flaps are high-lift devices, located at the inboard wing trailing edge sections. When deflected or lowered, the flaps provide increased lift at lower airspeeds, enabling steeper landing approach glide paths without an increase in the approach airspeed. Slats, which are extended from the wing leading edge, are also high-lift devices that increase the wing lift at low speeds.
There are several different types of wing flaps and slats, of varying mechanical complexity and aerodynamic effectiveness, which are discussed in Chapter 3. Spoilers, which extend upward from the wing's upper surface, reduce or “spoil” the lift, to assist the aeroplane in slowing down and descending.
They are also deployed after landing, to “dump” the wing lift and transfer the aeroplane’s weight from the wings to the landing gear, which improves braking. Spoilers can also be used as a means of aeroplane roll control when deployed differentially (extending from one wing and not the other).
Airplane Configurations
Aeroplanes come in all shapes and sizes. Usually, the configuration of an aeroplane is driven, or at least strongly influenced, by its mission requirements. For example, a commercial airliner has a large fuselage cabin area due to the requirement to transport passengers. A military fighter jet may have a highly swept wing to allow it to fly a supersonic ally.
A utility aeroplane that must be able to take off and land on snow might have skis for landing gear. These are a few examples of aircraft configurations that may be driven by the mission requirements.
It may be possible to satisfy the mission requirements with a variety of design solutions, limited only by the imagination and creativity of the aeroplane designer, and influenced by advancements in technology.
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