GROUND LOOP

GROUND LOOP - The ground loop is a uncontrolled turn during ground operations that may occur while taxiing, takeoff, but especially during after-landing roll.  It is not always caused by drift or weathervaning, but these can cause the initial swerve.  Careless use of the rudder, an uneven ground surface, or a soft spot that retards one main wheel of the airplane may also cause a swerve.  In any case the initial swerve causes the plane to ground loop.  Due to the characteristics of  a tailwheel airplane, the forces that cause a ground loop increase during a swerve.  The initial swerve causes inertia and this acting on the CG (which is located behind the main wheels), swerves the plane even more.  If allowed to continue, the force may become great enough to cause the outer wingtip to strike the ground or collapse the landing gear.

    If the plane touches down while drifting or in a crab, the pilot should apply aileron to the high wing while applying rudder to stop the swerve.  Brakes should be used only when rudder is insufficient to correct the swerve or turn.  Brakes must be used with caution because it is easy to overcorrect and aggravate the situation.  If brakes are used, sufficient pressure should be applied to the wheel on the outside of the turn to stop the swerve.  When the swerve has stopped, the new direction must be maintained until the plane has slowed to taxi speed, or stopped.