What happened
The incident occurred during a flight training exercise involving a helicopter. The flight instructor was demonstrating a touchdown autorotation maneuver. During this procedure, the aircraft touched down while maintaining forward momentum. As the helicopter slid along the ground surface, it came to an abrupt stop and lifted slightly onto the tips of its skids before settling back down.
During this dynamic event, the main rotor blades made contact with the tailboom. The impact occurred in the area forward of the tailrotor assembly. The force of the collision was sufficient to sever the tailboom completely.
The investigation
The physical evidence indicated that the primary mechanical failure resulted from the interaction between the rotating main rotor system and the rear fuselage structure. The specific point of failure was located on the tailboom, just forward of where the tailrotor is mounted. There were no indications of pre-existing structural defects in the tailboom prior to this event.
Findings
The sequence of events suggests that the sliding touchdown created an unstable attitude for the aircraft. The sudden stop and subsequent lift onto the skid tips likely altered the pitch or roll angle of the fuselage relative to the main rotor disk. This geometric change allowed the main rotor blades to descend into the path of the tailboom. The lack of sufficient clearance between the rotating blades and the tail structure during this specific phase of flight led to the catastrophic structural failure.