[rtkwe]

You can't pull autorotation with fixed pitch blades, at least not in any meaningful manner. Light quads can fall pretty slowly with pinwheeling motors but that's not actually autorotation. The way a helicopter is able to autorotate is to pull negative pitch, which spins the rotors using the fall energy of the copter, then shortly before crashing pulling back to positive pitch and using the still spinning blades to slow down to a controlled landing.

For motor failure ETH Zurich has some research out there about recovering to normal(ish) flight after a prop loss. The quad goes into a pretty rapid spin but it's still controllable, link below to an outside the lab test.

https://www.youtube.com/watch?v=ek0FrCaogcs