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26 UAV industry based on existing aircraft; it chose Pipistrel as its design and manufacturing partner. The Slovenian company reduced cost and development time by drawing on its portfolio of legacy platforms, choosing a design it describes as “an aircraft of the most stable category”. The result is a single-engine, tractor- propeller-driven monoplane measuring 6.3 m long with a 9.5 m wingspan, a total wing area of 12.6 m 2 , a single-tube tail boom, a single fixed vertical stabiliser with a large rudder and an all-moving tailplane with a trim tab. Underneath this base vehicle, Wings For Aid worked with Pipistrel and industrial design agency VanBerlo/ Accenture to replace the cockpit with a large structural cargo pod. This contains the box release mechanism and its control system, as well as the mission avionics and the attachment points for the aircraft’s diagonal wing-bracing struts and tricycle- style landing gear. The result, Koperberg says, is a combination of proven technology with what is effectively a new fuselage and flight control system (FCS) designed and built to European Aviation Safety Agency standards. The lift-to-drag ratio of the aircraft in its new configuration is estimated at 9.0, with a claimed drag coefficient of 0.05, although the actual figure will emerge from flight testing, Koperberg says. Its aerodynamics were developed and refined using CFD packages including OpenFOAM. The wings and tail surfaces are moulded from CFRP composites, while the tail boom is an aluminium alloy tube. The new cargo pod/fuselage is a tubular steel spaceframe structure covered by a shell made in left and right halves constructed from a sandwich of carbon fibre and epoxy skins around a honeycomb core. Access to the cargo space is by a pair of composite doors on each side of the cargo bay. The box drops from two-part hatches in the floor, each of which forms part of the modular release mechanism, of which there are four in the pod that deploy two boxes each. The complete air vehicle with the cargo pod integrated stands 2.9 m high, and has a maximum take-off weight of 641 kg. Koperberg says the high wing configuration adds to the UAV’s stability while providing easy access to the cargo space and keeping the propeller well clear of the ground to minimise the risk of it being hit by any debris from unprepared landing strips. The final height is determined by that of the fuselage pod and the landing gear, and was carefully chosen to optimise the ergonomics to make loading as easy as possible. The chosen powerplant is a Rotax 582 UL two-cylinder liquid-cooled two-stroke rated at 48 kW (65 hp) at 6500 rpm and 75 Nm of torque at 6000 rpm. Fuelled by a pair of Bing 54 carburettors, the 29.1 kg engine drives a four-blade fixed- pitch propeller designed and built for the application by Pipistrel, with an emphasis on noise reduction. The electrical system is divided into 13.2 V and 28 V circuits. The 13.2 V side powers the starter motor, engine electrics, cargo release mechanism December/January 2021 | Unmanned Systems Technology Dossier | Wings For Aid MiniFreighter 8/500FW A lot of development and testing went into the guide rails that keep the aid boxes straight and promote a smooth exit from the aircraft (Courtesy of Wings For Aid) The high wing configuration adds to the UAV’s stability, provides easy access to the cargo space and keeps the propeller clear of the ground