65 such as a two-cylinder gasoline boxer engine or a hydrogen fuel cell, to recharge the batteries powering its four electric wing-mounted nacelles (and its single electric tail motor) and thereby fly for up to 3 hours. The company estimates that each 4 kg of payload costs an hour of flight endurance or 133 km of range. It also emphasises that range extenders will be customer-specific and will therefore be engineered to their individual requirements. The powertrain options are changed via the nose cone, which has a hinged opening that also serves as the cargo bay, much like the cargo storage design of the Pterodynamics X-P4 trans-wing UAV (issue 41, December 2021/January 2022). The bay can take containers of up to 600 x 400 x 330 mm. Regardless of energy source though, the Aero2’s five e-motors give it a cruising speed of 150 kph to optimise energy consumption. Having so many motors contributes to the need for safety through redundancy: if one rotor should break, or a single motor or controller per wing should fail, some extent of continued flight or a controlled landing should be possible. The UAV is also designed with flight control redundancy, with two flaps and two ailerons per wing and redundant flight control units. Dufour’s development of the Aero2 is ongoing, although the Swiss company has announced partnerships with some key suppliers for additional prototypes and potentially serial production. These include Aerolite for the UAV’s composite structural parts, Connova for its composite airframe, and Suter Industries for the fellow Swiss company’s TOA-288 engine (detailed in issue 34, June/July 2020). “Suter offers the best solution for our hybrid-electric propulsion system,” Bendrey says. “The first version of this hybrid unit has been intensively tested with a view to further modifications that will help us put the aircraft on the market.” In Germany, aerospace company Volocopter (last discussed in issue 37, April/May 2021, regarding its VoloCity eVTOL air taxi and VoloDrone UAV) has partnered with ADAC Luftrettung. The latter is an air rescue organisation, also based in Germany, and plans to use some of the former’s eVTOL aircraft in rescue services and medical flights. At the 2023 Paris Air Show, ADAC Luftrettung announced that it had signed an order for two VoloCitys. The air rescue non-profit also signed a deal officially signifying its intention to buy another 150 of them as part of the partnership. The VoloCity is a 900 kg MTOW aircraft with 18 electric rotors distributed across its 11.3 m-diameter carbon composite airframe. Entirely battery-powered, it can fly up to 35 km between charges and at airspeeds of up to 110 kph, with a maximum payload of 200 kg. Although ADAC Luftrettung’s fleets currently consist largely of helicopters for rescue and intensive care operations, the two companies have been working together since 2018 on CAD simulations which indicate that introducing eVTOLs into life-saving medical rescue flights could provide technical, operational and sustainability advantages. It was following those test results that ADAC Luftrettung reserved two of the VoloCitys, which it has now bought. It is expected that the two UAVs | Insight The structure and systems of the Aero2 have to be safe and aerodynamically efficient, and delivering that is not easy Uncrewed Systems Technology | August/September 2023 ADAC Luftrettung has signed up for two VoloCitys to supplement its helicopter fleets in air rescue work (Courtesy of Volocopter)
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