Variable-sweep wing

A variable-sweep wing, colloquially known as a "swing wing", is an airplane wing, or set of wings, that may be swept back and then returned to its original position during flight. It allows the aircraft's shape to be modified in flight, and is therefore an example of a variable-geometry aircraft.

Typically, a swept wing is more suitable for high speeds, while an unswept wing is suitable for lower speeds, allowing the aircraft to carry more fuel and/or payload, as well as improving field (take-off and landing) performance. A variable-sweep wing allows a pilot to select the correct wing configuration for the plane's intended speed. The variable-sweep wing is most useful for those aircraft that are expected to function at both low and high speed, and for this reason it has been used primarily in military aircraft.

A number of successful and experimental designs were introduced from the 1940s into the 1970s; however, the recent advances in flight control technology and structural materials have allowed designers to closely tailor the aerodynamics and structure of aircraft, removing the need for variable sweep angle to achieve the required performance; instead, wings are given computer-controlled flaps on both leading and trailing edges that increase or decrease the camber or chord of the wing automatically to adjust to the flight regime. This is another form of variable geometry, although it is not commonly called such.

The 1931 Westland-Hill Pterodactyl IV was a tailless design whose lightly swept wings could vary their sweep through a small angle during flight. This allowed longitudinal trim in the absence of a separate horizontal stabiliser.

Later, experimental aircraft were built to study the effects of a simple swept wing. The first of these was the Messerschmitt Me P.1101 whose sweep angle could be changed on the ground. World War II in Europe ended before the P.1101 could be completed.

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