Uncrewed Systems Technology 049 - April/May 2023

62 has found that the noise of a helicopter is not overly disruptive, in the sense that people are generally used to the sound and don’t always stop what they’re doing to look up – at least when the helicopter is at high altitude. But the same sound level from a drone is unfamiliar, so it distracts people and disrupts their behaviour, hence the propensity for accidents or at least complaints.” Additionally, and strange as it might sound, Eurolink has found through researching such reports that the spectral density of most multi-rotors’ noise output is profoundly upsetting to dogs. As such, greater noise generation from UAVs over urban areas is almost guaranteed to trigger secondary waves of noise from them, creating a nuisance. To show a potential workaround, Eurolink therefore worked with Niccolo Cusano University (Unicusano) in Rome to again draw on lessons from nature, this time to find a quieter way to fly. “It is well-known that owls are highly successful night hunters, despite that being the quieter part of each day. They are effective because their wings and feathers produce lownoise,” Lapiana explains. “Unicusano has a very good drone laboratory, and has built up a lot of experience and talent with drones over the past several years,” he adds. “They also conduct UAV experiments with primary international aerospace manufacturers. “So with the university’s help, we decided to try to duplicate this, to make a digital twin of an owl’s wing or feather so that we could simulate, calculate and extrapolate how to achieve the same low-noise qualities in the physical shape of a drone’s propeller.” Unicusano had done some virtual evaluations along these lines before, and after a fresh range of software- based studies for Eurolink, some prototypes were built and tested in the university’s wind tunnel. The results were almost identical to those predicted in simulations. Eurolink continues to work with Unicusano for laser sintering and cutting its low-noise propellers in series production, although carbon fibre propellers are still offered as standard for customers who aren’t flying near populated areas. “As a result, we achieved a reduction in noise fromthe propellers in flight at 250 ft in height, as requested by the FAA, of around 8-9dB comparedwith the oneswe had previously used,” Lapiana says. “We also tested our noise output versus that of the smaller 7.5 kgDJI Matrice 300UAV, andwe were producing one-ninth the noise of it. “It took a lot of work, but given that all our experience was in avionics, robotics and AI, and none in aerodynamics, we didn’t want to leave this critical aspect of UAV engineering to chance, or to try some exhausting trial-and-error approach.” Eurolink AI Given Eurolink’s decision to avoid hobbyist or Chinese-made components, its selection of avionics and computer systems tends to be skewed to the West. However, the Beluga has been designed to suit users worldwide, so the company emphasises that there is no one best autopilot or comms system; it opts for the most suitable for a specific market, application or airworthiness requirements or rules. After testing and approving what it saw as the most state-of-the-art autopilots on the market, and the most capable of supporting the Beluga in the long term, the George autopilot from uAvionix has become one of its most frequently used flight controllers. The George is built around a Cube (from Cubepilot). Two George models are currently available, the G2 and G3. The G2 weighs 68 g, has nine servo/ ESC interfaces (and two CAN interfaces), and incorporates uAvionix’s microLink 2 x 2 MIMO BVLOS C2 radio and pingRXpro dual-band ADS-B receiver. The G3 weighs 99 g, has one CAN port and 12 servo/ESC ports, with additional serial and ADC inputs to enable external ADS-B, GNSS, and comms options. Both systems consume power at a nominal rate of 2.5 W, and are validated to operate from -10 to +55 oC. Eurolink also says autopilots from MicroPilot and Embention have been used April/May 2023 | Uncrewed Systems Technology An optional larger cargo bay with 14 litres of storage can be installed in the undercarriage