Definition
In helicopter flight, autorotations are a flight condition in which the main rotor is driven by air flowing up through the rotor disc rather than by engine power. They are used as the standard procedure for landing a helicopter safely after an engine failure or other loss of powered drive to the rotor.
Plain English
If a helicopter loses engine power, the pilot can still land safely by letting the upward flow of air through the rotor blades keep them spinning. That spinning rotor acts like a parachute and gives the pilot enough lift and control to glide down and touch down.
Context Anchor
Seen in helicopter emergency procedures, simulated engine-failure training, and discussions of power loss during instrument flight.
Derivation
From 'auto-' (Greek autos, meaning self) and 'rotation' (Latin rotatio, a turning). Literally 'self-turning' — the rotor keeps turning on its own, without the engine driving it.
Why Pilots Care
Provides the only safe way to land a helicopter after total engine failure.
Analogy
Think of a maple seed falling from a tree. As it drops, the air rushing up through its blades makes it spin, and that spinning slows its fall. A helicopter in autorotation behaves the same way.
Grounding Statement
Picture a helicopter descending with the engine no longer powering the rotor, while the air rising through the rotor keeps the blades turning.
Intuition Check
Autorotation does not mean the helicopter flies automatically. It means the rotor turns without engine power because airflow is driving it.
Example Sentence 1
During training, the instructor demonstrated autorotations by reducing power and letting the rotor maintain its speed from the upward airflow.
Example Sentence 2
In actual flight the pilot lowered collective immediately to begin autorotations after the engine failed.