Definition
A rapid, self-sustaining oscillation of a flight control surface or other aerodynamic structure, caused by the interaction of aerodynamic forces, structural elasticity, and inertia. Once started, flutter can build in amplitude very quickly and lead to structural failure of the affected component.
Plain English
A fast, vibrating shake of a part of the aircraft — like a wing, aileron, or elevator — that can grow worse on its own and tear the part apart if not stopped.
Context Anchor
Seen in airframe maintenance, control-surface balance, aircraft speed limits, and reports of unusual vibration in flight.
Derivation
From the Old English 'floterian,' meaning to float or flap about. The everyday image of a flag flapping in the wind captures the same idea: a flexible surface oscillating in an airflow. In aviation, the oscillation is dangerous because the structure feeds energy back into itself rather than damping out.
Why Pilots Care
Uncontrolled flutter can quickly destroy control surfaces or wings, leading to loss of the aircraft.
Grounding Statement
At the wrong speed, a tiny shake in a wing or control surface can be fed by the airflow until it becomes a violent vibration.
Intuition Check
Flutter does not mean a light, harmless trembling here. In aviation, flutter means a dangerous vibration that can build quickly and damage the aircraft.
Example Sentence 1
After repainting the aileron, the technician rebalanced it carefully to prevent flutter at high airspeeds.
Example Sentence 2
Designers added mass balance weights to the elevator to raise its natural frequency and prevent flutter at cruise speeds.