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82 August/September 2017 | Unmanned Systems Technology PS | UAVs for research I n February 1946, Britain’s Air Ministry threw away the nation’s lead in the technology of supersonic flight when it cancelled the Miles M52, an experimental jet aircraft designed to be capable of flying at 1000 mph at 36,000 ft – even though the first of a planned three prototypes was on schedule to make its maiden flight within months (writes Peter Donaldson). The ministry’s excuse was that the risks of flying so far into the unknown were too great to ask test pilots to take, and so future supersonic flight research would be done with radio-controlled models. It later emerged though that a long list of top Royal Air Force and Royal Aircraft Establishment pilots who were to have flown it had in fact been compiled. However, the ministry’s mendacity inspired many eager volunteers to try to persuade it to change its mind, including a former Luftwaffe pilot who said that nobody would mind if a former enemy pilot were to break his neck! Sadly this was to no avail, and Chuck Yeager took the lead for the US when he flew the Bell X1 past Mach 1 over the Rogers Dry Lake in the Mojave Desert in California in October 1947. While a fictional plan to use unmanned systems helped kill Britain’s early work on supersonic flight, they now have a central role in manned flight research. Unmanned sub-scale research aircraft serve where computer simulations and wind tunnel tests won’t do, and where the risks are deemed too great for human test pilots or the associated costs thought too high. For example, Area 1’s Prototype- Technology Evaluation Research Aircraft (PTERA) was originally developed to meet a NASA requirement for a sub- scale test aircraft resembling a typical small airliner to test new circulation control wing (CCW) technology intended to enable shorter take-offs and landings. In a CCW, high-pressure air from the engines or separate compressors is blown over the leading and trailing edges of the wings to generate extra lift. The CCW work was carried out at NASA’s Armstrong (formerly Dryden) Flight Research Center. The agency’s requirement called for the PTERA to be able to fly with or without the CCW equipment, so Area 1 designed it to be reconfigurable and modular. Another version, known as the Generic Modular Aircraft T-Tail, was built for NASA to investigate the extremes of deep stall and recovery behaviour of such aircraft, in which the turbulent air from the stalled wings kills the lift on the tail, eliminating its ability to pitch the nose down to recover the main wing from the stall. The first PTERA is now being used in a cooperative programme carried out by NASA’s Armstrong, Langley and Glenn centres to research the spanwise adaptive wing concept, in which the outer portions of the wings fold as far as 75° up or down to reduce drag and increase lift in different areas of the flight envelope. This is an old idea being examined again now that new, more compact actuator technologies can reliably articulate thin aerofoil sections. As these UAVs cost about $250,000 each, losing one is unlikely to break the budget if you are NASA – or a former enemy’s neck. Now, here’s a thing “ ” There was a former Luftwaffe pilot who said that nobody would mind if a former enemy pilot were to break his neck!