Airplanes

Airplane, also called AEROPLANE, or PLANE, any of a class of fixed-wing aircraft that is heavier than air, propelled by a screw propeller or a high-velocity jet, and supported by the dynamic reaction of the air against its wings. Two kinds of aircraft without fixed wings that are classified as airplanes are the STOL airplane and the VTOL airplane. A brief treatment of airplanes follows.

For treatment of historical aspects, see Transportation; for manufacturing technology, see Industries, Manufacturing; for military aspects, see War, The Technology of.

The essential components of an airplane are a wing system to sustain it in flight, tail surfaces to stabilize the wing, movable surfaces (ailerons, elevators, and rudders) to control the attitude of the machine in flight, and a power plant to provide the thrust to push the craft through the air.

An enclosed body (fuselage) houses the crew, passengers, and cargo, as well as the controls and instruments used by the navigator. An airplane also requires a support system (such as wheels or pontoons) when it is at rest on a surface and during takeoff and landing.

Most airplanes in use today are monoplanes (i.e., aircraft with a single pair of wings). They are termed high-wing when the wing is attached at the top of the fuselage, midwing when it extends from or near the centre of fuselage section, and low-wing when the wing structure fastens to the fuselage structure at the bottom. The multiplane with two or more horizontal wing systems, one above the other, connected by a series of struts and wires, has virtually disappeared.

The few biplanes still in service are used mainly for sport flying or for agricultural crop dusting. Monoplanes may be characterized by the planform (top view) of their wings, which may be rectangular, tapered, swept-back, or delta. A so-called variable-geometry concept incorporating adjustable sweepback is a compromise to obtain good high- and low-speed characteristics from the same wing.

For takeoff and landing, hinged wing panels are extended at right angles to the fuselage in order to utilize the advantages of long-span and high-aspect ratio. For high speed and maneuvering in flight, the panels are swung rearward to make (with the tail surfaces) a delta configuration. The normal location for stabilizers, fins, rudders, and elevators is well behind the wing, mounted on the tapered tail section of the fuselage.

The standard arrangement (until the advent of jet engines) was a cruciform assembly, with vertical fins and rudders and horizontal stabilizer and elevators forming a cross, the axis of which was approximately coincident with the fuselage axis.