Aircraft

Aeroplanes

A size comparison of some of the largest aircraft in the world. The Airbus A380-800 (largest airliner), the Boeing 747-8, the Antonov An-225 (aircraft with the greatest payload) and the Hughes H-4 "Spruce Goose" (aircraft with greatest wingspan).Aeroplanes or Airplanes are technically called fixed-wing aircraft.

The forerunner of the aeroplane is the kite. A kite depends upon the tension between the cord which anchors it to the ground and the force of the wind currents. Kites were the first kind of aircraft to fly, and were invented in China around 500 BC. Much aerodynamic research was done with kites before test aircraft, wind tunnels and most recently computer modelling programs became available.


A collection of NASA test aircraftAeroplanes are generally characterized by their wing configuration.

In a conventional configuration, the main wings are placed in front of a smaller stabilizer surface or tailplane. The canard reverses this, placing a small foreplane forward of the wings, near the nose of the aircraft. Canards are becoming more common as supersonic aerodynamics grows more mature and because the forward surface contributes lift during straight-and-level flight. The tandem wing type has two wings of similar size, one at the front and one at the back. In a tailless design the lift and horizontal control surfaces are combined. The ultimate expression of this is the flying wing, where there is no central fuselage, and perhaps even no separate vertical control surface (e.g., the B-2 Spirit).

Sometimes two or more wings are stacked one above the other. A biplane has two wings, and a triplane has three, quadruplanes (four) and above have never been successful. Up until the 1930's, biplanes were the most common. Triplanes were only occasionally made, especially for a brief period during the First World War due to their high manoeuvrability as fighters. Since the Second World War, most aeroplanes have been monoplanes. A sesquiplane is similar to a biplane, but with the lower wing much reduced in size. Most multi-plane designs are braced, with struts and/or wires holding the wings in place. A monoplane has only one wing. Some, especially early designs, are also braced, because this allows a much lighter weight than a clean, unbraced cantilever design. But bracing causes a large amount of drag at higher speeds, so it is no longer used for faster designs. Monoplanes are also classified as high-wing, mid-wing or low-wing, according to where on the fuselage the wing is attached.

Most low-speed aeroplanes have a straight wing, which may be constant-chord, or tapered so that it decreases in chord towards the tip. For flight near or above the speed of sound, a swept wing is usually used, where the wing angles backwards towards the tips (though forward sweep is occasionally experimented with, and M-wing designs which reverse direction half way along have been suggested). A notable variation is the delta wing, which is shaped like a triangle: the leading edge is sharply swept, but the trailing edge is straight; one common form is the cropped delta, which merges into the tapered swept category, and an especially graceful form is the double-curved ogival delta found for example on Concorde. Another variation is the crescent wing, seen for example on the Handley Page Victor, which is sharply swept inboard, with reduced sweep for the outboard section. A variable-geometry wing, or swing-wing, can change the angle of sweep in flight. It has been employed in a few examples of combat aircraft, the first production type being the General Dynamics F-111.

Seaplanes and Floatplanes differ in that a seaplane has the bottom of its fuselage shaped hydrodynamically and it sits directly on the water when at rest, while a floatplane has two or more floats attached below the rest of the aircraft so that the fuselage remains clear of the water at all times.

Some people consider wing-in-ground-effect vehicles to be aeroplanes, others do not. These craft "fly" close to the surface of the ground or water. An example is the Russian ekranoplan also nicknamed the "Caspian Sea Monster". Man-powered aircraft also rely on ground effect to remain airborne, but this is only because they are so underpowered - the airframe is theoretically capable of flying much higher. (Hovercraft are not considered to be aircraft, since they rely wholly on the pressure of air on the ground beneath, and have no aerodynamic lifting surface).