Definition
The smallest radius an aircraft can pivot through on the ground when its nosewheel (or tailwheel) is deflected to its maximum steering angle. It defines the tightest ground turn the aircraft is physically capable of making and is used to determine whether the aircraft can negotiate taxiways, ramps, and turnarounds.
Plain English
The tightest circle the aircraft can make when taxiing with the steering turned all the way to one side.
Context Anchor
Seen in discussions of aircraft performance, steep turns, maneuvering near the ground, and obstacle avoidance.
Derivation
Radius comes from a Latin word meaning a spoke or ray from the center of a circle. That helps because a turning aircraft is moving around part of a circle, and the turning radius is the distance from the center of that circle to the aircraft.
Why Pilots Care
Determines whether an aircraft can safely complete a U-turn on a runway or maneuver within the available space on taxiways and ramps.
Grounding Statement
At the same speed, a steeper bank makes the turn tighter; at the same bank angle, a faster airplane makes a wider turn.
Intuition Check
Minimum does not mean the smallest turn you can force by pulling harder. It means the smallest turn the aircraft can safely make without exceeding its limits or getting too close to a stall.
Example Sentence 1
Before taxiing onto the narrow ramp, the pilot checked that the aircraft's minimum turning radius would allow it to clear the parked aircraft on either side.
Example Sentence 2
Knowing the minimum turning radius helped the crew decide if they could safely reverse direction on the active runway.