Definition
A flight condition in a helicopter where the main rotor system is driven by air flowing up through the rotor disc rather than by engine power. It is used as an emergency procedure following an engine failure, allowing the pilot to make a controlled descent and landing without engine power.
Plain English
When a helicopter loses engine power, the rotor blades keep spinning on their own because air flows up through them as the helicopter descends. The pilot uses this spinning to glide down and land safely.
Context Anchor
Seen in helicopter emergency procedures, especially engine-failure training and practice landings without engine power.
Derivation
From 'auto-' (Greek, meaning 'self') and 'rotation.' Literally 'self-rotation' — the rotor turns itself, without engine drive, using only the upward flow of air through the disc.
Why Pilots Care
It is the only way to land a helicopter safely after a complete engine failure; every helicopter pilot must master the entry, glide, and flare to survive power loss.
Analogy
Think of a maple seed (samara) falling from a tree. As it falls, air spinning past its wing makes it rotate on its own, slowing the descent. A helicopter in autorotation works on the same principle.
Grounding Statement
Picture the helicopter descending while air moving up through the blades keeps them spinning fast enough for the pilot to control the landing.
Intuition Check
Autorotation does not mean the helicopter flies itself, and it does not mean the engine is still driving the rotor. It means airflow during descent is keeping the main rotor turning.
Example Sentence 1
After the engine quit, the pilot immediately entered an autorotation and set up for a landing in the field below.
Example Sentence 2
During the autorotation practice the student flared at the proper height to reduce descent rate before touching down.