Primary finding
Probable cause
Abnormal ground contact during an autorotation demonstration, resulting in a severed tailrotor driveshaft.
Investigator assessment
Analysis narrative
The helicopter instructor was demonstrating a full down 180 degree auto rotation. He reported that everything was done normally and as he flared to slow the aircraft down, the tail skid lightly bumped the ground a couple of times. The skids eventually made contact with the ground and the helicopter slid about 20 feet to a stop. A post landing examination of the helicopter revealed that the main rotor blade had contacted the tailboom, severing the tailrotor drive shaft.
Source record
Factual narrative
The helicopter instructor was demonstrating a full down 180 degree auto rotation. He reported that everything was done normally and as he flared to slow the aircraft down, the tail skid lightly bumped the ground a couple of times. The skids eventually made contact with the ground and the helicopter slid about 20 feet to a stop. A post landing examination of the helicopter revealed that the main rotor blade had contacted the tailboom, severing the tailrotor drive shaft.