Definition
The movement of a flight control surface (such as an aileron, elevator, or rudder) away from its neutral position, which alters the airflow over the wing or tail and produces a change in the aircraft's attitude or flight path.
Plain English
How far a control surface is moved from its resting position when the pilot moves the controls. The more it moves, the bigger the effect on the aircraft.
Context Anchor
Seen in aerodynamics explanations of lift, especially when the handbook discusses Newton’s Third Law and how a wing affects the air around it.
Derivation
From the Latin 'deflectere', meaning 'to bend away' or 'turn aside.' In aviation, the control surface is literally bent or turned away from its neutral position.
Why Pilots Care
Understanding deflection explains how control inputs and wings produce forces, helping pilots anticipate aircraft response during instrument flight.
Grounding Statement
Picture air flowing toward the wing in one direction, then leaving slightly downward after the wing has acted on it.
Intuition Check
Do not read deflection as just “damage,” “bending,” or a gauge needle moving. In this context, it means the air’s path is being turned by the wing.
Example Sentence 1
A small deflection of the ailerons was enough to start a gentle turn.
Example Sentence 2
Increased rudder deflection turned the airplane by pushing air to the left.