Hover to Forward Flight Transition – Longitudinal Motion Feasibility Study of a Converted Long Endurance Fixed-Wing VTOL UAV

Abstract

The flight performance limitations of fixed wing Unmanned Aerial Vehicles (UAV) and drones can be solved by merging the strength of both types of vehicles. By making a fixed wing UAV capable of vertical takeoff and land (VTOL), the flight-envelop and mission capabilities can be increased. Although some researchers have proposed designing a totally new hybrid aircraft with these capabilities, the work published here proposed incorporating a relatively simple quadrotor type system on existing successful fixed wing airframe to provide the VTOL capability, capitalizing the best from an already successful UAV. The study is focused on the converted aircraft longitudinal motion during transition from hover to forward flight. XFLR5 was used to obtain the aerodynamic coefficients and then, MATLAB and SIMULINK simulated the flight dynamic responses. The results show that the best transition performance is achieved when both the 4 rotors and the internal combustion (IC) engine are engaged together during the transition, producing no lost in altitude. The study also found that in the event the 4 rotors failed simultaneously during the transition, the aircraft can still complete the transition with only the IC engine functioning at 40N of thrust.