What happened
The incident occurred while the pilot was maneuvering the helicopter into a hover position adjacent to the designated parking area. During this phase of flight, the aircraft experienced a sudden mechanical failure involving the tail rotor drive shaft. In response to the loss of anti-torque control, the pilot initiated an attempt to perform a hovering autorotation.
However, during this critical maneuver, the pilot did not apply collective pitch. Consequently, the helicopter descended rapidly and collided with the ground while maintaining a right skid-low attitude. Upon impact, the aircraft rolled over onto its right side, coming to rest in that orientation.
The investigation
Following the accident, investigators conducted a detailed examination of the helicopter's mechanical components. The focus was placed on the tail rotor drive shaft assembly. Analysis revealed significant wear on the splines connecting to the upper universal joint. Additionally, excessive wear was observed on the splines located at the transmission output shaft.
Findings
The mechanical failure of the tail rotor drive shaft was the primary event that precipitated the accident. The subsequent loss of control was exacerbated by the pilot's failure to apply collective pitch during the attempted hovering autorotation. These factors combined to cause the ground collision and rollover.