Preliminary Design of a Highly Efficient VTOL System Based on Tethered Fixed-Wing Aircraft

The need for highly efficient VTOL aircraft capable of long endurance flight motivated the Vertical Flight Society, in 2016, to form their 34th Student Design Competition around designing an aircraft capable of hovering for a duration of 24 hours with a 176 lb (80 kg) payload. This paper presents the preliminary design of the Swarm, a configuration of the Electric Powered Reconfigurable Rotor (EPR2 ) concept, drafted by the joint Universite de Sherbrooke and ´ Georgia Tech team. The Swarm, comprised of a central fuselage tethered to three electrically propelled unmanned fixed-wing aircraft flying in a circular trajectory, achieves its goal through rotor reconfiguration. Throughout the flight, the fixed-wing aircraft modify their trajectory and airspeed to optimize performance and minimize fuel burn rate. A hybrid-electric powerplant in the fuselage supplies power via conductive tethers to the fixed-wing aircraft. The design and reconfiguration were optimized using a 2-step time-marching optimization. The designed system greatly exceeds the competition requirements by accomplishing 31 hours of hover flight using readily available technologies and COTS components. The Swarm, weighing a maximum of 2,700 lb (1,224 kg), requires only between 62 and 120 hp (46-89 kW) to perform hover out of ground effect. Safety, reliability and maintenance analyses were also conducted, in addition to estimating production and operational costs of the system