28 Dossier | ACC Thunder Wasp UAV You can just cut out the bent part of the metal and put a riveted cover over it. It’s field-repairable, as a multicopter should be in serious operations.” Also critical was simplicity, which Claes notes is difficult to engineer. But he and his crew envisioned creating a UAV that could be handled by one person wearing gloves in a -20 C snowstorm, so mechanical and conceptual simplicity were taken into account with every drawing, iteration and modification. “Engineers can make vehicles with amazing capabilities if they just make them as complicated as they like, but that means extremely high costs, lengthy manufacturing times and onerous certification processes,” Claes says. “So, achieving simplicity has required testing and validating a few very good ideas, and also using COTS products. That might sound very different to using many customised components, like other uncrewed systems manufacturers do, but it greatly reduces our costs compared with using bespoke devices. “And, more importantly, it means our subsystems have largely been out in the industry for years, made mature and reliable through hundreds of thousands of operating hours, meaning they’re also extremely well-documented for traceability and certification processes.” Lastly, alongside development of the uncrewed aircraft, considerable money has been invested in developing effective patents to protect ACC Innovation’s IP, provide comprehensible technical explanations of it to interested customers or investors, and to not accidentally tread on the content of anyone else’s patents. With these guiding principles, the first Thunder Wasp prototype was built in 2019, using carbon fibre, as well as a significant amount of glass fibre, and a Hayabusa engine. Lacking the company’s desired physical robustness, the next version was built around a welded chassis composed of 0.8 mm-thick, flight-certified, square steel tubes, with carbon-composite covers forming the body over the steel skeleton. “But we couldn’t make it simple to assemble, or achieve the stiffness and strength we wanted, so we moved to using riveted aluminium sheets, as have been used in aviation since the 1940s, and are still used in most professional aircraft engineering and manufacturing today,” Claes recounts. The third rendition started with rudimentary boxes of aluminium sheet, and after highly promising initial tests, a further version was built with sheets of dual aluminium sandwiching a foam core. While this increased strength and stiffness, the added manufacturing complexity was ultimately deemed excessive, with aluminium sheets alone being sufficiently strong, very lightweight and incredibly easy to work with. “Today, we build nearly every structural part with 0.4 mm-thick aluminium sheets, which is almost as thin as kitchen foil, but when we put them together to construct a Thunder Wasp, they’re really very stiff and strong,” Claes says. “We brought in a top carbon fibre expert to judge if we would benefit from switching to carbon fibre. In less than five minutes of inspecting the Thunder Wasp GT, he told us to keep doing what we were doing: he could see no way of improving it with carbon.” H marks the spot Looking down at the Thunder Wasp GT from above, the fuselage takes the shape of a large, metallic ‘H’, with each of the four corners mounting a single rotor for propulsion, as well as rudders for attitude and yaw control, and a gas turbine engine mounted atop the middle of the central bridge portion of the fuselage that joins the two ‘rotor pylons’. The autopilot is placed inside that central portion, as close to the middle (and the CoG) as possible for accurate flight control, behind a riveted panel that can be removed for easy diagnostics or replacement of the autopilot. Two CAN buses extend from the autopilot: one for the engine, and one for the avionics and data network, both of which can be accessed by technicians anywhere along the aircraft anatomy. GNSS antennas for redundancy and heading are located atop the front and rear, equidistant between the reach of the rotor-blade tips, to keep the propellers from blocking nav-critical signals from space. “Having a distance between those antennas is key for GNSS compassing, and additional antennas for comms are placed between our landing struts at the front and back,” says Max. December/January 2025 | Uncrewed Systems Technology The engine sits over the central part of the fuselage, with the autopilot beneath it, and the fuel tanks further down below
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