Aviation glossary

Autorotation

A flight condition in which airflow through the rotor keeps it spinning without engine power. Lets a helicopter land safely after a power failure.

Autorotation is the key safety principle of every helicopter. When engine power is lost the freewheel unit disengages the rotor from the transmission and the pilot immediately lowers the collective to keep rotor RPM in the operating band — air flowing up through the descending disc drives the rotor. The helicopter descends along a defined glide angle (roughly 1:4 on the Cabri G2) and just before touchdown the pilot trades speed and RPM in a flare for a soft landing. Autorotation is trained from the first solo flight onward and is part of every helicopter pilot check.

Related terms

Helicopter
A rotorcraft whose engine-driven main rotor produces both lift and thrust. Can hover, fly in any direction and land almost anywhere.
Collective control
The lever to the left of the pilot that changes the pitch of all rotor blades simultaneously. Sets total thrust — climb or descent.

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