A concept proposed in the 1940s is being dusted off as the US Defense Advanced Research Projects Agency (DARPA) reveals plans for an oblique flying wing (OFW) X-plane demonstrator. The tailless supersonic demonstrator is aimed at future aircraft concepts demanding high speed and long range.
In the late 1940s and early 1950s, US aerodynamicist R T Jones demonstrated that an obliquely swept wing with elliptical load distribution minimised both wave and induced drag. In the UK, Handley Page proposed an oblique flying-wing design during the studies that led eventually to Concorde.
In the 1970s, NASA's Ames and Dryden research centres joined forces to flight test the oblique-wing concept using the AD-1, a small, subsonic research aircraft designed by Burt Rutan and built by Ames Industrial. The single-seat, twin-turbojet AD-1 was flown 79 times between 1979 and 1982, reaching speeds up to 175kt (320km/h) with the wing pivoted to sweep angles up to 60°.
An OFW aircraft would take off and land with zero or low sweep, the flying wing slewing in flight to higher sweep angles as speed increases. Previous studies indicated Mach 1.4 at 68° to be the optimum cruise condition. Studies also suggest the sonic boom of an OFW will be less than that of a conventional supersonic aircraft.
Under its OFW advanced technology demonstration programme, DARPA plans to tackle the challenges of aerodynamic control, aerostructural design and propulsion integration. The agency plans flight tests of an X-plane demonstrator as well as ground testing of operationally representative subsystem components.
Source: Flight International
