Plain English Meaning

A small flap on the back edge of a flight control that automatically moves the opposite way when the pilot moves the control, helping push the main surface and making it easier to fly the aircraft.

Full Definition

A small auxiliary control surface attached to the trailing edge of a primary flight control (such as an aileron, elevator, or rudder) that is mechanically linked to move in the opposite direction to the main control. This opposing movement creates an aerodynamic force that helps move the primary surface, reducing the physical effort the pilot must apply to the controls.

Context Anchor

Seen in aircraft flight control system descriptions, , and discussions of how are reduced.