Lilium Pegasus outwash in hover

Abstract

This report analyzes the outwash of the 7-seat Lilium Pegasus (L4-100/MK12) (mass 3175 kg/wingspan 14 m), an electric VTOL jet, using electric ducted propellers with thrust vectoring, see Fig. 1. The outwash was computed by Lilium with an in-house CFD code, and the wake was analyzed by DLR for maximum velocity, PAXMAN forces and overturning moments, and compared with the Airbus H145 helicopter, which is similar in mass and passenger number. The outwash from a single main rotor helicopter is approximately axisymmetric. The main rotor down wash is turned outward by the ground, forming an annular jet, reducing in strength with distance. The outwash can cause lifting, tipping or instability of persons or objects near the aircraft. Multirotor aircraft generate more outwash fore and aft of the aircraft and less outwash to the side of the aircraft. Maximum downwash velocity increases linearly with increasing aircraft mass, and decreasing rotor area. The shape of the Lilium jet outwash is qualitatively similar to that for tilt-wing aircraft.