Incident Overview
A helicopter on a training flight experienced a tail rotor and gearbox separation during shutdown following a hard landing. The helicopter was being operated by a student pilot holding a commercial rating and a certified flight instructor (CFI). The student pilot had been issued a current qualification card with a provision requiring additional training and a reevaluation check ride.
Autorotation Maneuver
The training flight involved practicing a straight-in autorotation. The student pilot executed a "very gradual" flare and allowed the helicopter to descend to approximately 10 feet above ground level (AGL) before she began rolling on the throttle. As she applied throttle, she inadvertently made an abrupt aft cyclic control movement.
Tail Rotor Strike and Recovery
The abrupt cyclic input caused the tail rotor and stinger to strike the ground before the CFI could regain control. The CFI successfully stabilized the helicopter in a hover of about 3 to 4 feet above the ground, during which he noticed a vibration. As he began to set the helicopter down, the vibration intensified.
Post-Landing Damage
During the shutdown sequence, the tail rotor and tail rotor gearbox separated from the tailboom. The extent of other damage was not specified.
Subsequent Training
Following the accident, the student pilot spent two weeks with the Army National Guard, where she received additional training in the UH-1H helicopter. According to a conversation between the CDF safety officer and the National Guard instructor pilot, the student continued to have difficulty with aircraft control.