Issue 41 Unmanned Systems Technology December/January 2022 PteroDynamics X-P4 l Sense & avoid l 4Front Robotics Cricket l Autonomous transport l NWFC-1500 fuel cell l DroneX report l OceanScout I Composites I DSEI 2021 report

22 T he professional UAV industry has spawned a multitude of approaches to producing safe and robust VTOL-transitioning systems. Most have taken the route of a multi- copter hybrid, such as those from Alti Transition ( UST 8, June/July 2016) with vertically disposed electric motors on fixed booms. Other manufacturers have developed tiltrotor aircraft, such as those from Quantum Systems ( UST 14, June/ July 2017) and Wingcopter ( UST 24, February/March 2019), or tail-sitters from the likes of Martin UAV ( UST 15, August/ September 2017) and UAV Works ( UST 32, June/July 2020). And the innovations continue. Take the case of US-based PteroDynamics, which has developed a unique VTOL-transitioning solution in which transversely folding wings move a UAV’s electric drives from a forward-facing arrangement for flight to one that points upwards for hovering. The company says the system, called the Transwing, has various advantages over other VTOL systems for fixed-wing UAVs, from better aerodynamics and agility to greatly reduced mechanical and software complexity, as well as a far smaller ground footprint relative to its in- flight dimensions. It is used on its flagship aircraft, the X-P4 UAV, which is on track for delivery to the US Navy next year. There is also a smaller version, the X-P2. The X-P4 is a 4 m wingspan all-electric aircraft, with a nominal MTOW of 75 lb (34 kg) and a maximum endurance of 3 hours when cruising at 45-50 knots (52-58 mph). It offers a 6.8 kg nominal payload weight (within a 28 litre payload volume), although up to 11.8 kg can be carried if the end-user is happy to sacrifice battery packs and hence range and endurance. Company history The Transwing technology was invented by Dr Val Petrov, founder and CTO of PteroDynamics, who moved to the US from the former Soviet Union in 1990 while still a PhD student, specialising in control theory and non-linear dynamics. This UAV’s unique VTOL-transitioning technology gives it advantages over other VTOL systems. Rory Jackson explains how it was developed Transition elements December/January 2022 | Unmanned Systems Technology