Plain English Meaning

How wide a circle the airplane carves when it turns. Faster speed means a bigger circle. Steeper bank means a tighter circle.

Full Definition

The horizontal distance from the center of a turn to the aircraft's flight path during that turn. Turn radius increases with the square of true airspeed and decreases as the bank angle steepens. For a given bank angle, a faster aircraft will sweep a wider arc through the sky.

Context Anchor

Seen when planning turns in the traffic pattern, maneuvering near terrain, or understanding how speed and bank affect the space needed to turn.

Derivation

comes from a Latin word meaning a spoke of a wheel or a line from the center outward. That helps here because turn radius is measured from the center of the turn outward to the aircraft, like the distance from the of a wheel to its rim.