![]() ![]() įor supersonic flight a delta-planform lifting body is more suitable than a simple ichthyoid. Subtle movements of the wings were able to induce the small deflections which controlled the direction of flight, while trim was maintained by adjusting the angle of sweep to compensate for the varying position of the centre of lift at different speeds. He conceived of a simple ichthyoid (fish-like) fuselage with a variable wing. His previous work on the stability of airships had impressed on him the high control forces that could be exerted on the body of an aircraft, through very small deflections. The added weight of the sweep and trim mechanisms eat into the performance gains, while their complexity adds to cost and maintenance.īy moving the wing pivots outboard and only sweeping part of the wing, the trim changes are reduced, but so too is the variation in span and accompanying operational flexibility.īritish engineer Barnes Wallis developed a radical aircraft configuration for high-speed flight, which he regarded as distinct from the conventional fixed-wing aeroplane and called it the wing controlled aerodyne. Some mechanism, such as a sliding wing root or larger tail stabiliser, must be incorporated to trim out the changes and maintain level flight. ![]() As the wing sweeps its centre of lift moves with it. However it has disadvantages which must be allowed for. Varying the sweep in flight allows it to be optimised for each phase of flight, offering a smaller aircraft with higher performance. However it also reduces the overall span of a given wing, leading to poor cruise efficiency and high takeoff and landing speeds.Ī fixed wing must be a compromise between these two requirements. Sweeping the wing at an angle, whether backwards or forwards, delays their onset and reduces their overall drag. 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.Ĭharacteristics Variable sweep Ī straight, unswept wing experiences high drag as it approaches the speed of sound, due to the progressive buildup of sonic shockwaves. The configuration was also used for a few fighter/ interceptor aircraft, including the Grumman F-14 Tomcat and the Panavia Tornado ADV. 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. Its greater complexity and cost make it practical mostly for military aircraft.Ī number of aircraft, both experimental and production, were introduced between the 1940s and the 1970s. The more efficient sweep angles available offset the weight and volume penalties imposed by the wing's mechanical sweep mechanisms. A variable-sweep wing allows the pilot to use the optimum sweep angle for the aircraft's current speed, slow or fast. These tradeoffs are particularly acute for naval carrier-based aircraft. Another is that the aircraft's fuel consumption during subsonic cruise is higher than that of an unswept wing. One is that the stalling speed is increased, necessitating long runways (unless complex high-lift wing devices are built in). These are simple and efficient wing designs for high speed flight, but there are performance tradeoffs. Most aircraft that travel at those speeds usually have wings (either swept wing or delta wing) with a fixed sweep angle. It allows the aircraft's shape to be modified in flight, and is therefore an example of a variable-geometry aircraft.Ī 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. 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 sweepĪ 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 straight position during flight. ![]()
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