What happened
During a demonstration of an autorotation, the helicopter experienced a hard touchdown. According to the pilot, the maneuver had progressed through a flare when he applied the maximum allowable power in an attempt to initiate a power recovery. This application of power resulted in a loss of directional control. The passenger noted that during the procedure, the pilot identified a landing spot located directly above the pedals.
The aircraft subsequently touched down firmly at an angle approximately 90 degrees from its direction of travel, resulting in a slight yaw upon impact. There were no injuries reported.
The investigation
Mechanical examination of the helicopter revealed several points of structural failure. The forward attachment fitting for the tailboom was found to be fractured. While both tail rotor blades remained attached to the hub and fork, one blade had fractured and separated at the spar root area near the end of the hub spindle; a dent was also noted on the leading edge near the tip.
Additionally, the tail rotor drive shaft was discovered to be twisted and had disengaged from the upper pulley aft drive adapter. Investigators examined the tailboom forward attachment fitting (P/N:269A2323) and its associated components, determining that the fracture surface was consistent with an overstress failure. No evidence of preexisting cracks was identified during the examination.