Variable-sweep wing

"Swing wing" redirects here; not to be confused with Swing Wing (toy).
"Variable fighter" redirects here. For the fictional vehicle, see VF-1 Valkyrie.

A variable-sweep wing, colloquially known as a "swing wing", is an airplane wing, or set of wings, that may be modified during flight, swept back and then returned to its previous straight position. Because it allows the aircraft's shape to be changed, it is a feature of a variable-geometry aircraft.

A straight wing is most efficient for low-speed flight, but for an aircraft designed for transonic or supersonic flight it is essential that the wing be swept. Most aircraft that travel at those speeds usually have wings (either swept wing or delta wing) with a fixed sweep angle. Whilst simple and efficient for high speed flight, these come at the cost of a higher stalling speed (necessitating long runways unless complex high-lift wing devices are built in), and higher fuel consumption during subsonic cruise. These tradeoffs are particularly acute for naval carrier-based aircraft. A variable-sweep wing allows the pilot to use the optimum sweep angle for the aircraft's speed at the moment, whether slow or fast. The more efficient sweep angles available offset the weight and volume penalties imposed by the wing's mechanical sweep mechanisms. Its greater complexity and cost make it impractical for most commercial applications and result in its use being primarily for military aircraft.

A number of aircraft, both experimental and production, were introduced between the 1940s and the 1970s. The majority of production aircraft to be furnished with variable-sweep wings have been strike-oriented aircraft, such as the Mikoyan-Gurevich MiG-27, Tupolev Tu-22M, and Panavia Tornado. The configuration was also used for a few fighter/interceptor aircraft, including the Mikoyan-Gurevich MiG-23, Grumman F-14 Tomcat, and the Panavia Tornado ADV. From the 1980s onwards, the development of such aircraft were curtailed by advances in flight control technology and structural materials which 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 technique is another form of variable geometry.

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