Low-Fidelity Aerodynamic Computational Simulation on a Fixed Wing-Multirotor Hybrid Unmanned Aerial Vehicle

Multirotor UAV is popular amongst rice paddy farmers in conducting crop spraying. However, the multirotor UAVs are too slow with short endurance while fixed wing VTOL UAVs are too fast and inefficient in conducting 17-m/s crop-spraying work. Therefore, a hybrid of multirotorfixed wing UAV is proposed as a solution. This hybrid is basically a fixed-tilt angle quadcopter mounted on fixed-wing airframe without separate propeller for forward thrust. The purpose of the study is to investigate aerodynamic characteristics of the hybrid UAV at different rotor speeds from 800 to 2000 rpm. Low fidelity computation such as Vortex-Lattice Method is used as computation method. The results show that the drag coefficients of 1400 to 2000 rpm are negative caused by higher amount of forward thrust compared with induced drag. The hybrid UAV is longitudinally, statically stable with positive stick-fixed static margins for all cases. Visualizations show that propeller wash does affect the longitudinal stability by reducing its horizontal tail effective area.