Editing Variable-sweep wing (section)

{{short description|Airplane wings capable of changing position to alter their geometry}}
{{redirect-distinguish|Swing wing|Swing Wing (toy)}}
{{Redirect|Variable fighter|the fictional vehicle|VF-1 Valkyrie}}
{{Use dmy dates|date=June 2021}}
{{use British English|date=October 2021}}
[[File:Dassault Mirage G8.jpg|thumb|Two [[Dassault Mirage G]] prototypes, the upper one with wings swept]]
[[File:Grumman F-14 Tomcat SDASM.jpg|thumb|A [[Grumman F-14 Tomcat]] testing an unusual asymmetric wing configuration, a possible in-flight failure case, showing one wing at minimum sweep and one at maximum sweep]]

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 [[Wing configuration#Variable geometry|variable-geometry]] aircraft.

A [[straight wing]] is most efficient for low-speed flight, but for an aircraft designed for [[transonic]] or [[Supersonic speed|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. These are simple and efficient wing designs for high speed flight, but there are performance tradeoffs. One is that the stalling speed is increased, necessitating long runways (unless complex high-lift wing devices are built in). Another is that the aircraft's fuel consumption during subsonic cruise is higher than that of an unswept wing. 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 practical mostly 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 [[Flap (aeronautics)|flaps]] on both leading and trailing edges that increase or decrease the [[Camber (aerodynamics)|camber]] or [[Chord (aeronautics)|chord]] of the wing automatically to adjust to the flight regime; this technique is another form of ''variable geometry''.