Oblique flying wing (OFW) aircraft could fly in close formation supersonically for significant fuel savings, according to a year-long study sponsored by the US Air Force Research Laboratory (AFRL).

The study was conducted by Bristol, UK based-Nangia Aero Research Associates in parallel with the US Defense Advanced Research Projects Agency's (DARPA) Switchblade OFW project.

Switchblade aims to demonstrate the feasibility of a variable-sweep, or oblique, tailess supersonic flying wing so the concept can be considered for an intelligence, surveillance and reconnaissance (ISR) aircraft or bomber in the 2020 timeframe.

The project includes plans for a sub-scale demonstrator. The attributes are that it must be tailless in supersonic cruise and subsonic loiter conditions, have air-breathing propulsion, be capable of conventional take-off and landing, have a cruise speed of at least M1.2, and be capable of varying sweep in flight from a minimum of 30° or less to a maximum of 60° or more.

"You could have, in formation or in a swarm, 10-plus oblique wing aircraft in a row [and achieve the fuel savings]," says Bristol, UK based-Nangia Aero Research Associates' consultant engineer, Raj Nangia.

He hopes DARPA will decide in the third quarter to build the demonstrator and that formation flying studies could be an option for Switchblade in future.

Nangia's AFRL sponsored work showed that in supersonic flight, lift-induced drag reductions of more than 35% for the trail aircraft could be achieved. This is comparable to the savings found in conventional transonic aircraft formation studies.

However in supersonic flight Nangia's study identified that the wing planform needs to feature "subsonic" leading edges, which means the leading edge is more highly swept than the Mach angle. Thus at M1.4 or M1.6, the leading edge needs to be swept at 60° to 65°.

Source: Flight International