SOURCE:Flight International
PICTURES & VIDEO: British team proves flapless flight with Demon UAV

Manoeuvring without the aid of control surfaces has been demonstrated by an unmanned air vehicle designed by a British team of industry and academic specialists.

The Demon UAV, an adapted BAE Systems Eclipse, first flew on 17 September with its flight control surfaces deactivated during a portion of the flight to test a new aerodynamic circulation control system.

The Demon relied on a thrust vectoring exhaust nozzle and blown air over the trailing edge of the wing to deliver the aerodynamic forces and moments normally provided by flaps, ailerons and elevators.



 © BAE Systems



The flight was considered a success by the flapless air vehicle integrated industrial research (FLAVIIR) programme, which includes BAE, Cranfield University and nine other UK universities.

"I feel sure I have witnessed a significant moment in aviation history," says Richard Williams, BAE programme director for future capability.

Such a circulation control system could be applied to reduce the size of the wing on widebody airliners. Maintenance may be less costly by replacing the moving parts of conventional control surfaces, which also account for a significant percentage of the aircraft's noise signature.

In military applications, the technology could create a new class of stealthy aircraft with a mould line uncompromised by moving control surfaces.

Williams says such a design "will help ensure we maintain both a level of sovereign capability and a competitive edge".

The Demon's fluidic flight controls guide air from the rectangular exhaust nozzle over upper and lower Coanda surfaces to establish pitch. Roll control is achieved by blowing bleed air over a Coanda surface installed on the trailing edge of the wing. By controlling boundary layer conditions, the fluidic controls can also provide greater lift or drag on take-off and landing.

The challenge for the FLAVIIR team will be to demonstrate that such a control system can deliver sufficient force throughout the aircraft envelope and especially at high angles of attack, where air flow over the wings is minimal.

Demon is expected to complete a two-year demonstraton programme to study its performance throughout its flight envelope.

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