How auto rotation is used to help land a helicopter safely if the engine fails?

Auto rotation is not used to help land a helicopter safely if the engine fails. Auto-rotation is used to keep a helicopter in the air if the engine does fail. Autorotation is the ability of a helicopter to descend in a controlled manner without power from the engine. This is achieved by using the rotor blades to create lift, just as they do when the engine is running. However, in autorotation, the rotor blades are driven by the airflow, rather than by the engine.

To enter autorotation, the pilot reduces the collective pitch of the rotor blades, which causes them to slow down. This creates a difference in airspeed between the top and bottom of the rotor blades, which generates lift. The pilot then uses the cyclic pitch of the rotor blades to control the direction of the helicopter's descent.

Autorotation can be a very effective way to land a helicopter safely in the event of an engine failure. However, it is a difficult manoeuvre to perform, and it requires a great deal of skill on the part of the pilot.