Unmanned Systems Technology 028 | ecoSUB Robotics AUVs I ECUs focus I Space vehicles insight I AMZ Driverless gotthard I InterDrone 2019 report I ATI WAM 167-BB I Video systems focus I Aerdron HL4 Herculift

Aerdron studied the benefits and drawbacks of that choice. It turned out that using eight motors would have been less cost-efficient and less energy- efficient, and would have yielded a lower ratio of payload capacity to empty craft weight. “While eight motors is ideal for redundancy, using that many would have also meant needing four more motor mounts, four more sets of electronic speed controllers, propellers, more power cabling and hardware, giving more overall empty weight and less payload capacity,” Marcos Fabian says. “If we could fly more than 25 kg MTOW legally then we might end up using more motors – as many heavy-lift UAVs do – but for this particular project’s objectives, four proved to be more efficient.” The HL4 also currently uses T-Motor’s G30x10.5 propellers. During early testing, the folding propellers previously selected were found to generate problematic vibrations during start-up. While it was initially suspected that they were folding during the motor start-up phase owing to the torque, video footage showed they were unfolding when the motor accelerated, then locked again when the centrifugal force increased. The size of the propellers – 76.2 cm in diameter, 26.6 cm in pitch – combined with the fast acceleration, torque and applied power they underwent during take-off, caused the hub centre lines to ‘break’ from their hold. The propellers were therefore switched to a non-folding type, and thereafter the start-up was far smoother and the vibration levels much lower. “T-Motor were hugely helpful after we sent them videos, data and technical explanations of what was happening,” Marcos Fabian recounts. “They immediately asked us to send the props back to where we’d bought them, and shipped fixed non-folding replacement props to us that worked perfectly. If we could fly more than 25 kg MTOW legally we might use more motors, but four proved to be more efficient for this project