To make an aircraft fly and manoeuvre safely without the use of conventional control surfaces is an achievement in itself; to do that while at the same time bringing together new construction techniques and new control mechanisms could be said to be over-ambitious ?but a British team of researchers has precisely done that. An unmanned air vehicle (UAV) showcasing a wide range of new technologies has successfully demonstrated ?flapless flight? in the UK.
The UAV, called Demon, made the historic flight from an airfield at Walney Island in Cumbria recently. Developed by Cranfield University, BAE Systems, and nine other UK universities, Demon represents the first alternative to the moving flap technology used since the early days of aviation, in which moving mechanical elevators and ailerons control the aircraft?s flight. Conventional control surfaces? many moving parts require frequent, costly repairs and account for a significant percentage of an aircraft?s noise output.
BAE Systems has offered to work with Defence Research and Development Organisation (DRDO) and other agencies to help India develop its autonomous UAV technology. Responding to an request for proposal for unmanned combat aerial vehicles, BAE Systems made this offer on UAV technology and collaboration to help India develop their own cutting edge capabilities.
So, what?s the big deal with the British breakthrough? Aviation analysts aver that the British machine has no moveable control surfaces. ?That?s right, no flaps, ailerons, elevators or spoilers. Just a wing, an engine and some holes. First of all, the exhaust nozzle is moveable, so it can be vectored around to aid in directional control. Also, bleed air from an APU (auxilliary power unit, meaning a small engine) is blown through hundreds of tiny holes in the trailing edge of the wing to also help with directional control.?
The military likes this because moveable surfaces like slots and flaps have edges and gaps, which are apparently total heat-scores when you are trying to have a low radar profile. Less edges to bounce off means more stealth, and that?s generally what defence researchers are going for when they build a small UAV, most of which are used to spy on people in some way. ?The advantages to this in a civilian application would be less moving parts, a stronger wing, less maintenance requirements and a cleaner wing which results in less drag, meaning less fuel burn. You could control the boundary layer across the wing with air jets, which would also help change lift/drag characteristics for takeoff and landing. ?We?ll see if anything comes of this, but it sure does look promising,? an analyst says.
The Demon UAV is shaped in a ?blended wing body? configuration, which allows it to mimic the aerodynamic forces normally provided by flaps, elevators and ailerons by blowing jets of air from a nozzle over Coanda surfaces installed across the wing. The flapless system, based on a concept called fluidic flight control, would require less maintenance and would produce less noise, affording the aircraft a more stealthy profile for military missions. It could also allow for planes with significantly reduced wing size.
The unmanned craft uses hundreds of tiny air jets to control its movement in flight rather than using traditional flap mechanisms. This new technology would give military aircraft a more stealthy profile by reducing edges and gaps that can be picked up by radar, said its developers.
Such an approach offers several advantages over ?moving flap? technology, in that it means fewer moving parts and a more stealthy profile for the aircraft. Demon?s trial flights were the first ?flapless flights? ever to be authorised by the UK Civil Aviation Authority.
The UAV successfully demonstrated flapless flight when, for a planned portion of a test-flight, the conventional flap control system was turned off and the aircraft flew and manoeuvred using the new technology. It promoted the development of the FLAVIIR (Flapless Air Vehicle Integrated Industrial Research) programme which led to the Demon demonstrator after laying down a ?Grand Challenge? to UK universities five years ago.
Richard Williams, BAE Systems programme director for Future Capability, says, ?What the FLAVIIR team have achieved in such a short time is nothing short of remarkable. What makes it even more poignant is that this is the result of British brains collaborating to produce world-leading technology. It, and other initiatives like it, will help ensure we maintain both a level of sovereign capability and a competitive edge.?
While Demon itself is not expected to become a production aircraft, a number of the technologies it contains have and will continue to filter through to a range of other aviation platforms.