what is autorotation in a Helicopter?

Answer 1

Autorotation in a Helicopter, means that you spin the main rotor by descending to the ground. the air that flows through the blades spin them and generate rpm that can later, in a case of engine failure, can be converted into lift to stop the decent and land safely.

Answer 2

(m)

Autorotation is a condition where the main rotor is allowed to spin faster than the engine driving it. How is that achieved? It is actually quite simple.
All helicopters are fitted with a free wheeling unit between the engine and the main rotor, usually in the transmission. This free wheeling unit can come in different forms but one of the most popular is the sprag clutch. The free wheeling unit will allow the engine to drive the rotors but not allow the rotors to turn the engine. When the engine/s fail the main rotor will still have a considerable amount of inertia and will still want to turn under its own force and through the aerodynamic force of the air through which it is flying. The free wheeling unit is designed in such a way to allow the main rotor to now rotate of its own free will regardless of engine speed. This principle is the same reason that if you are in your car and you push your clutch in, or put it into neutral while the car is still moving, the car will coast along under it's own force. This occurs regardless of what you do to the accelerator pedal.

Answer 3

It is when a helicopter is about to crash and the pilot uses the main rotor to slow up the free fall to make the landing a have a little less impact....