[mrexroad]

In case anyone else is interested in the not-at-all-obvious-answer [1], I’ll save you the google: autorotation

> Autorotation is the ability of a helicopter to in some situations have its rotors powered by the flow of air rather than the engine. In short, as the helicopter descends, the upward directed flow of air pushes through the rotors, makes them rotate faster, which in turn provides lift.

[1] https://www.highskyflying.com/can-helicopters-glide/

[mixmastamyk]

Still, isn’t it more likely for the occupants to survive when a plane lands without power, assuming a decent landing spot?

[fsckboy]

a helicopter can "glide down" just like an airplane. if your engine fails, with the aid of the rotor as you descend you can turn the potential energy of being up in the air into forward motion, and that forward motion will generate lift over your rotor blades. You practice these techniques as part of getting a license.

see the "dead man's curve" which relates to having an engine failure with insufficient height or lateral speed (helicopters shouldn't hover in place unless a good ways up) https://en.wikipedia.org/wiki/Helicopter_height%E2%80%93velo...

[mixmastamyk]

Agreed, however forward motion works for a plane landing with wheels. A helicopter with "skis" sounds less effective.