How does autorotation work in helicopters?

Question

Autorotation is when a helicopter loses power to its engines and the rotors begin to spin due to air resistance. Pilots can then safely land the helicopter because of this

But I just don’t understand how it works. Surely if the helicopter is falling then the air will push the rotors in the opposite direction to how they normally spin and that won’t create lift? Can someone explain?

In: 2

Answer 1

Rotor blades don’t create lift by generating downwash alone. They create lift because their blades are shaped like wings with the top of the blade curved and the bottom flat. The mechanism that controls the pitch of the blades attaches to the front of the blade, that means when air pushes up on it like when it’s falling the trailing edge of the blade moves up which would cause the blades to rotate the correct direction when falling.