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

23 Although he spent much of his subsequent professional life in investment management, he took up aeronautics as a hobby, mainly through remote control (RC) planes and helicopters. “I spent more than 20 years flying RC, and I’d always wanted to combine my planes and helicopters into a single aircraft,” he recounts. “I especially wanted to combine a high-aspect ratio wing, which is ideal for highly efficient and fast forward flight, with a VTOL capability. But long, thin wings make aircraft hard to control when they’re anywhere near the ground, especially with crosswinds that can ‘catch’ and pull them around. That’s why most VTOL-transition engineers opt for relatively short wings, despite being less aerodynamically efficient for flight.” Dr Petrov ruminated on this until 2016, when he began conceiving a way to fold his aircrafts’ wings (partially influenced by the Sto-Wing technology patented by Grumman for the F4F-4 Wildcat) using a rearwards-folding element to direct its propellers upwards. After building parts for a prototype from balsa wood, he iterated many blueprints of wing-folding until arriving at one he thought would work. He constructed the mechanisms, installed them in the 3 lb aircraft (along with rudimentary RC electronics and controls), and found to his shock that it transitioned from vertical take- off into forward flight without any issues. Recognising what his technology was capable of, he hurriedly patented it and sought partners to start a company. A new prototype with a slightly improved transitioning mechanism was built and entered testing in mid-2017, which accomplished about 200 flights before crashing because of an aileron servo failure. “We’ve built prototypes of many different MTOWs and wingspans, and found that the Transwing technology scales without any difficulties,” Dr Petrov adds. “The first 4 m wingspan prototype was critical to proving that: if we were prone to any wind stall on larger wings, it would have shown up in one of its test flights. Instead, transition and flight were performed perfectly, with high controllability at all speeds and power outputs.” The company began pitching its design to potential customers in 2018, shortly after Matthew Graczyk joined as CEO. The following year, the US Navy asked to test a Transwing aircraft, awarding PteroDynamics a contract for the Blue Water ship-to-ship logistics project soon after; the X-P4 was subsequently designed around this requirement. Vice-president of engineering Tim Whitehand joined PteroDynamics in early 2020. He is a seasoned engineer and aviator experienced in the design, build and testing of numerous unmanned and optionally piloted experimental aircraft, and worked to establish a team of engineers focused on maturing the company’s technologies, processes and capabilities. PteroDynamics X-P4 | Dossier Unmanned Systems Technology | December/January 2022 PteroDynamics’ transitioning architecture is computationally simple and allows a high aspect ratio wing (Images courtesy of PteroDynamics) The Transwing uses its four electric motors in cruise, forward flight and transitions between the two