Plain English Meaning

How far the ailerons are tilted away from their flat, resting position. When you turn the yoke, the ailerons move — one goes up, the other goes down — and that movement is the deflection.

Full Definition

The movement of an aileron up or down from its neutral position when the pilot turns the control wheel or moves the stick sideways. One aileron deflects upward while the opposite aileron deflects downward, changing the lift produced by each wing and causing the airplane to roll.

Context Anchor

Seen in stall and spin discussions, especially when explaining why pilots are usually taught not to try to pick up a dropped wing with aileron during a stall or .