Incident Overview
A helicopter instructor was demonstrating a full down 180-degree autorotation maneuver. The instructor reported that the procedure was executed normally. During the flare to slow the helicopter, the tail skid lightly touched the ground on two occasions. Subsequently, the skids made contact with the ground, and the helicopter slid approximately 20 feet before coming to a stop.
Post-Landing Inspection
A post-landing examination of the helicopter revealed that the main rotor blade had contacted the tailboom. This contact resulted in the severing of the tailrotor drive shaft. No other damage was reported in the inspection.
Sequence of Events
The instructor stated that all actions during the autorotation were performed as standard. The initial light contacts of the tail skid occurred during the flare. After the skids settled on the ground, the helicopter slid, and the main rotor blade struck the tailboom, cutting the tailrotor drive shaft.