Performance of Electric Vertical Take-Off and Landing (EVTOL) hovering craft

Simple analysis is used to predict the performance of a class of battery powered fan/propeller/rotor powered ultra-light craft capable of hovering with an all-up weight limit of around 2 kN. The influence of key parameters is presented, in particular their impact on flight endurance. It is shown that stationary hover endurances of around 12 minutes, without ground effect, are feasible using currently available lithium-ion cells. It is also predicted that endurances of around 24 minutes are feasible using market emerging lithium-sulphur cells with specific energy levels in excess of 400 Wh/kg. Possible hybrid electric motor plus piston engine design solutions capable of longer flight endurances are only briefly discussed.