The wind resistance of the "egretta" tail-sitter vtol uav

For Vertical Takeoff and Landing (VTOL) unmanned aerial vehicle (UAV), the wind resistance capability during takeoff and landing is the key to determine its practical application. In this paper, a tail-sitter VTOL UAV named Egretta has been introduced. To reveal its wind resistance capability, analytical equilibrium criteria in the longitudinal motion were derived. Then flight tests of the Egretta were carried out to identify the equilibrium states. It was found that the equilibrium states of the Egretta at hovering exist for wide pitch angles ranging from 10.58° to 90°. The corresponding stable flight speed is in the range of 15.02 to 0 m/s. As a result, the wind resistance capability of the Egretta during takeoff and landing is up to wind stage 7.