In aviation, a ground loop refers to the rapid circular rotation of an aircraft in the horizontal plane whilst on the ground. This situation, analogous to an automobile oversteering into a skid, causes the "inside" wing to rise, thus causing the "outside" wing to scrape the ground. In severe cases (particularly if the ground surface is soft), the outside wing can dig in, causing the aircraft to skid violently or even cartwheel.

Conventional landing gear is set up with two wheels near the front of the plane and one smaller "taildragger" wheel, which is sometimes steerable, at the rear of the plane. This configuration is commonly referred to by the slang term "taildragger". Tricycle landing gear, on the other hand, has one steerable nose wheel set near the front of the plane, and a main pair of wheels set approximately under the middle of the wing, by far the predominant modern configuration. Both can be found in either a fixed or retractable subtype.

The ground loop phenomenon is predominantly associated with aircraft that have conventional landing gear, due to the centre of gravity being positioned behind the main wheels. It can also occur with tricycle landing gear if too much force is applied to the nosewheel, relative to the speed of the aircraft while on the ground. If the aircraft heading is slightly different than the aircraft's direction of motion, a sideways force is exerted on the wheels. If this force is in front of the centre of gravity, the resulting moment rotates the aircraft's heading even further from its direction of motion. This increases the force and the process reinforces itself. To avoid a ground loop, the pilot must respond to any turning tendency quickly, while sufficient control authority is available.

When ground loop occurs, it is usually in the context of an aircraft moving under its own power - either taxiing, landing, or during takeoff. Ground loop can cause extreme damage to the undercarriage and wingtips of an aircraft. Several incidents of ground loop have resulted in fatalities.

Aviation risks