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28 Dossier | Wings For Aid MiniFreighter 8/500FW and a ballistic parachute that acts as an emergency recovery system. The 28 V side runs the FCS, computers, actuators and comms systems. The FCS, which is provided by Amazilia Aerospace, is based on avionics components already proven in other manned and unmanned FCS developments. Owing to the time frame and the verification procedures required, the initial focus has been on redundant manual remote piloting functions, but the system is ready for automatic missions without requiring hardware upgrades. The flight control laws are currently being adapted to the flight dynamics of the aircraft and will be verified during an upcoming series of flight tests. The cargo pod/fuselage is designed around the modular and automated box release mechanism, which Koperberg describes as simple and safe with inherent redundancy. It is controlled by the company’s own algorithm that times the release for accurate targeting of the drop location. The MiniFreighter has also been designed for ease of maintenance through quick exchange of avionics modules in the field. “We have made sure that everything is accessible and can be changed easily,” Koperberg says, pointing out a pair of large access panels for the avionics aft of the main cargo doors. “Moving from region to region, for instance, we might need to change the radios or upgrade the whole flight control system after a year. Everything has been built for easy access so that local operating partners can also change parts on the aircraft.” Ease of access is also critical to the aircraft’s transportability, as it has to be disassembled for packing and then reassembled when it gets to where it is needed. Design details that contribute to this include the routing of push-pull cables that run along the outside of the tail boom to the elevator. Engineers and designers worked together on the aesthetics of the aircraft, sometimes having to make compromises. The cargo bay fuselage was developed for aerodynamic efficiency together with the designers’ input for an attractive-looking product. On the other hand, the engine itself is not cowled, even though the designers would have preferred that it was. It has been a subject of discussion between both parties but because cowling would change the airflow around the engine and its heat exchangers, and significantly increase development time, it was decided to keep it out of the design. Design, prototyping and initial manufacturing of the release mechanism were carried out at facilities run by VanBerlo/Accenture. The design and manufacturing of the complete aircraft, including the new fuselage/cargo pod, was handled by Pipistrel. Development challenges In addition to the short time frame, the principal challenges the programme has had to face included producing an efficient cargo pod/fuselage structure that is strong enough without taking up too much of the maximum take-off weight. This, Koperberg notes, involved a trade-off between time and weight. “Pipistrel has indicated that, given more time and more resources, it could optimise the inner structure further – the steel frame is super-strong,” he says. “Once we know more about the behaviour of the aircraft as a whole, we can think about different combinations of fuselage shell and frame, but given that we had such a short period of time, we decided we could live with the weight. “Of course, lower weight would save some fuel and allow for slower stall speeds and so on.” Pipistrel also developed the landing gear specifically for the aircraft. The single nose wheel is mounted at the end of a substantial oleo-pneumatic leg, the fixed upper steel tube of which is attached to the fuselage frame by triangulated tubing of smaller diameter and bolted joints. The main gear uses Pipistrel’s proven composite technology. The landing gear is a heavy-duty system designed to withstand rough treatment, Koperberg says. “Drones can have a bit of a bumpy ride, especially on landing, so it caters for the absorption of much more impact than the gear fitted December/January 2021 | Unmanned Systems Technology The Rotax engine remains uncovered, as it was in the original aircraft, to avoid having to recertify it because of the resulting aerodynamic changes (Courtesy of Wings For Aid)