Oblique Wing

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Oblique wing research aircraft NASA AD-1 with the wing rotated by 60 °, the maximum angle of rotation.

With Oblique wing (obliquely from frz./engl. Oblique =, oblique and English. Wing = wing / airfoil) is the concept of a rotating about the vertical axis wing for planes referred to. In older sources, the term "swivel wing" (from eng. Swivel = pivot point) is also used. A German term for this concept is "Scherenflügel". The oldest examples of this technology are the unrealized German aircraft projects Blohm & Voss P.202 and Messerschmitt Me P.1009 -01 from 1944, but it is not known which German expression was used for it at the time. The term "rotary wing" is already used for the rotors of helicopters and gyroscopes , and the term swivel wing usually refers to aircraft with non-continuous, symmetrically pivoting wings. The oblique wing concept, however, is a special variant of the swivel wing.

A special sub-variant is that of a flying wing aircraft with this concept, which is known as the Oblique Flying Wing (OFW).

definition

In aircraft with an oblique wing, a continuous wing is rotated around a central pivot point so that half of the wing moves in the direction of flight and the other half moves in the opposite direction. In this way, the air resistance can be reduced at high flight speeds, while the slow flight characteristics are maintained by turning back to the starting position. From the vertical take-off position, the wing can only be turned forward in one direction of rotation and, when returning to the landing position, turned back in the opposite direction of rotation. During the transition from take-off to fast cruise, the same side of the wing is always rotated in the direction of flight (e.g. only the right side as with the NASA AD-1). A complete rotation through 360 ° is not possible.

history

Little is known about the Blohm & Voss P.202 (with a shoulder- wing design) and Messerschmitt Me P.1009-01 ( double-decker design with two oppositely rotating wings above and below the fuselage) projects begun in 1944 known. These projects did not get beyond the drawing board stage. Information about the underlying experiments and calculations from that time are, however, in the dark.

It is known that Richard Vogt was significantly behind the development of the P.202. Numerous unusual aircraft projects were worked on under his leadership. Richard Vogt came to the USA via Operation Paperclip after the Second World War and worked there initially in a research laboratory of the United States Air Force , and later at Boeing . At the end of the Second World War, numerous documents fell to the Allies as spoils of war. So it is hardly surprising that the US began to deal with the subject from 1945.

There Robert T. Jones , an aeronautical engineer at NASA's Ames Research Center on Moffett Field , California , dealt with this concept and with the arrowhead theory of wings. Analytical studies and wind tunnel tests indicated that an oblique wing aircraft the size of a transport aircraft , which should fly at speeds of up to Mach 1.4 (1.4 times the speed of sound) , would have better aerodynamic properties than one with conventional wings.

As the only manned aircraft based on this concept, the NASA AD-1 was built to research this concept. A number of test flights have been made with it since 1979.

theory

The underlying idea is to build an aircraft whose efficiency remains as high as possible as the Mach number increases from take-off to cruising speed (M ~ 0.8, for a commercial aircraft). Since different types of air resistance are relevant for both flight conditions, it is difficult to implement this in a single aircraft.

If the Mach number is low, the induced drag , which arises when creating lift, is of greater importance. Airplanes and gliders taking off are exposed to particularly high levels of induced drag. One way to reduce this is to increase the wing aspect ratio. This is why particularly long, narrow wings are used in gliders. A wing with an infinite span would have no induced drag. At low speeds, during take-off and landing, the wing of an oblique wing aircraft would therefore be positioned perpendicular to the fuselage axis, like a conventional wing, in order to achieve maximum lift and controllability. As the speed increased, the wing would be rotated to achieve a more inclined angle, thereby reducing air resistance and fuel consumption.

With Mach numbers in the range of the speed of sound and beyond, the so-called wave resistance is of greater importance. The displacement of air creates a pressure wave. By pivoting the wings back away from the aircraft nose, you can keep them out of the pressure wave (see also arrow ). This significantly reduces air resistance. However, with increasing sweep of a wing, the wing extension is also reduced. At high speeds in the subsonic and supersonic range, you can adjust the wing up to an angle of 60 ° to achieve better high-speed performance with an oblique wing. Studies have shown that these angles reduce aerodynamic drag, resulting in higher speeds and greater range with the same fuel consumption.

In principle, it does not seem possible to design an aircraft in such a way that it is completely optimized for both flight conditions. However, the oblique wing design is a promising approach to approach this ideal. Due to the actively adjustable sweep with increasing Mach number, great efficiency can be achieved for a large range of different speeds.

In theory, one can thus achieve significantly better conditions for commercial transport flights by saving fuel and also being able to reduce aircraft noise in the vicinity of airports. For the military, among other things, there would be the possibility of a fighter with a very long range and flight duration.

OFW airliner research project by NASA

NASA has already undertaken investigations for an oblique flying wing aircraft (OFW) as a commercial aircraft . In 1991 a preliminary design study for an SAW supersonic airliner with 500 seats was carried out. On the basis of this study, a small remote-controlled demonstration model with a 6.10 m span was built. This model flew only once, for four minutes. But during this time it was possible to carry out a stable flight while the wing was adjusted from a sweep of 35 ° to 50 °. Despite this success, the high-speed research program and other SAW studies were canceled.

OFW project of DARPA

The Defense Advanced Research Projects Agency (DARPA) has signed a US $ 10.3 million contract with Northrop Grumman for the preliminary planning and risk reduction for a test aircraft in the form of an SAW demonstration aircraft. This aircraft is also known as the Switchblade .

The program aims to build a demonstration aircraft to examine the multiple challenges of such a radical design. The intended aircraft would be a pure flying wing aircraft, the wing of which can be moved in a rotary motion so that one side points in the direction of flight and the other side in the opposite direction. This configuration promises a combination of high speed, range and flight duration. The program consists of two parts: The aim of phase 1 is to form the theoretical foundations and to produce a conceptual design. In phase 2 an aircraft is designed, built and tested in flight. The result will be a collection of data that can be used for future military aircraft designs.

Wind tunnel tests for the aircraft have now been completed. The construction was rated as "workable and robust".

Individual evidence

  1. ^ [1] Three-sided view and description of Blohm & Voss P.202 on Luft46.com
  2. ↑ [2] Three-sided view and description of the Messerschmitt Me P.1009-01 on Luft46.com
  3. ^ G. Warwick - Flight International , No. 5029, Vol 169, page 20.
  4. ↑ Information about the DARPA project ( Memento from April 21, 2006 in the Internet Archive )
  5. ↑ Detailed technical analysis of the SAW concept ( Memento from May 14, 2006 in the Internet Archive )
  6. ↑ New Angles: Wind tunnel results point way forward for tailles oblique flying wing study, Aviation Week and Space Technology, October 8, 2007, pp. 34-35.

Web links

See also