Plain English Meaning

How wide a circle the airplane carves through the air when it turns. A tight turn has a small radius; a wide, sweeping turn has a large radius.

Full Definition

The horizontal distance from the center of an airplane's turn to its flight path, measured perpendicular to the direction of travel. Turning radius increases with the square of true airspeed and decreases as the angle of bank increases.

Context Anchor

Seen when practicing steep spirals and other ground-reference maneuvers, especially when trying to stay a consistent distance from a selected point on the ground.

Derivation

Radius comes from Latin and originally meant a spoke of a wheel or a ray from a center point. That helps here because turning radius is the distance from the center of the turn to the airplane’s path, like the distance from the of a wheel to its rim.