Definition 1 of 2
Definition
An uncontrolled, rapid horizontal rotation of an aircraft about its vertical axis while on the ground, typically during takeoff roll, landing roll, or taxi. Ground loops occur most often in tailwheel aircraft, where the center of gravity is behind the main landing gear, making the aircraft directionally unstable on the ground. Once a swerve begins, the rearward center of gravity tends to amplify the turn rather than damp it out, and if not corrected promptly with rudder and brake the aircraft can pivot sharply, often damaging a wingtip, landing gear, or propeller.
Plain English
A sudden, sharp spin of the aircraft on the ground, where the tail swings around and the airplane pivots out of control before the pilot can stop it.
Context Anchor
Encountered in takeoff, landing, taxi, and tailwheel-airplane handling discussions.
Derivation
The term combines 'ground' (the surface the aircraft is rolling on) with 'loop' (a rotational, circular motion). Together they describe a loop made on the ground rather than in the air, distinguishing it from an aerobatic loop.
Why Pilots Care
A ground loop can damage landing gear, propellers, or wings and may result in a runway excursion or injury.
Grounding Statement
Picture the airplane starting to swerve on rollout, then the swerve tightening until the airplane pivots around instead of continuing straight.
Intuition Check
A ground loop is not an aerobatic loop performed near the ground. It is a loss of control while the aircraft is rolling on the ground.
Example Sentence 1
The student pilot relaxed on the rudder during rollout and the Cub began to ground loop before the instructor caught it.
Example Sentence 2
Tailwheel airplanes are more prone to ground loops if the pilot does not keep the tail firmly on the runway.