Oblique wing

Encyclopedia : O : OB : OBL : Oblique wing

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The Oblique wing, Ames-Dryden-1 (1979), is another example of a variable geometry aircraft. The wing of this aircraft can turn on its center pivot. Therefore the wing can change its sweep angle and hence reduce its drag. The mechanism can turn in only one direction.

An oblique wing aircraft is the white stag of modern aeronautics. The general idea is to design an aircraft that performs with high efficiency as the Mach number increases from takeoff to cruise conditions (M ~ 0.8.) Since two different types of drag dominant in each of these two flight regimes, uniting high performance designs for each regime into a single airframe is problematic.

At low Mach numbers induced drag dominates drag concerns. Airplanes during takeoff and gliders are most concerned with induced drag. One way to reduce induced drag is to increase the aspect ratio of the lifting surface. This is why gliders have such long, narrow wings. An ideal wing has infinite span and induced drag is reduced to a two dimensional property.

Alternatively, at Mach numbers increasing towards unity, wave drag dominates design concerns. As the aircraft pierces the air, a sonic wave is generated. Sweeping the wings away from the nose of the aircraft can keep the wings aft of the sonic wave, greatly reducing drag. Unfortunately, for a given wing design, increasing sweep decreases the Aspect Ratio.

Fundamentally, it appears that no design can be optimized for both flight regimes. Which brings us to the oblique wing. By actively increasing sweep as Mach number increases, high efficiency is possible for a wide range of speeds. No such aircraft has yet proven capable of realistically providing these benefits.

An oblique flying wing could drastically improve air transportation, reducing fuel costs and noise in the vicinity of airports. Military operations include the possibility of a long endurance fighter/attack vehicle.

Oblique Flying-Wing

An oblique flying wing (OFW) is a flying wing (an aircraft with no other auxiliary surfaces such as tails, canards or a fuselage) where the wing is swept with one side of the aircraft forward, and one backwards in an asymmetric fashion[link]. This aircraft configuration is believed to give it a combination of high speed, long range and long endurance.[link] The United States Defence Advanced Research Projects Agency (DARPA) has awarded Northrop Grumman a $10.3 million (USD) contract for risk reduction and preliminary planning for an X-plane OFW demonstrator.G. Warwick - Flight International, Num 5029, Vol 169, Pg 20.

Successful flight of an OFW has many challenges, including issues associated with flight control and aerodynamics caused by the aircraft's asymmetric nature. There has also been investigations into an OFW platform being developed into a transcontinental airliner.[link]

See also

• Switchblade (airplane)

Notes and References

• http://www.darpa.mil/tto/programs/ofw.htm
• http://www.mwilliams.info/archives/006093.php
• http://www.aerodyn.org/Wings/ofw.html

 

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