Building of a manned copter with a gasoline engine.

[Bill Berson]

The Curtis Wright Quadrotor crashed when a shaft broke, fortunately in hover. The outcome would be disaster at 50 feet.
From my mini drone, I notice extreme vortex interactions that occur at near ground level. Much worse than a single rotor.
The V-22 had some Vortex Ring State crashes. Almost all VTOL crashes are fatal.
The power shafting might get extreme load variation. Would need expert design of shafting to understand torsional vibration.