Unmanned Systems Technology 021 | Robot Aviation FX450 l Imaging Sensors focus l UAVs Insight l Liquid-Piston X-Mini l Riptide l Eurosatory 2018 show report l Zipline l Electric Motors focus l ASTS show report

26 CoG remains ahead of the main wing as before, but the nose-down pitching moment is countered by the lift from the foreplane ahead of it, so there is no deliberately induced negative lift to counter. The foreplane is also the main pitch control surface. The stall resistance comes from the fact that the foreplane is set to stall before the mainplane would, dropping the nose to reduce the angle of attack, thereby preventing the mainplane from actually stalling. The one caveat here is that a violent pitch-up manoeuvre in a critical airspeed band could impart enough momentum into the foreplane to continue rotating the nose up to the point at which the mainplane stalls. As essentially an Intelligence, Surveillance and Reconnaissance (ISR) aircraft, it is not intended to perform any aggressive aerobatic manoeuvres. Guy says, “It’s nice to tell the autopilot not to do something, and as long as you put the right numbers in it behaves itself.” Although aggressive manoeuvring is out, he says, the FX450 must be able to withstand gusts that might subject it to higher g -forces. While the ISR mission shouldn’t require accelerations of any more than 3 g , he notes, “You’ve really got to assume it’s a 6 or 7 g day. A human pilot can fly it and someone’s going to ham fist it, it’s a training issue,” he says, emphasising that it must also withstand occasional rough handling by operators. Besides stabilising the UAV in yaw and contributing to directional control with the rudders, the winglets minimise drag by eliminating the vortices that would otherwise form at the tips as high- pressure air under the wing forces its August/September 2018 | Unmanned Systems Technology Canard foreplanes with split elevators provide pitch control with redundancy and inherent stall protection for the mainplane within defined manoeuvring limits (Courtesy of Robot Aviation) The FX450’s three pitot tubes are elements of the triple-redundant flight control system, each providing an input to the autopilot (Photo by the author)