What happened
While operating in cruise flight, the pilot of the helicopter detected a severe vibration. The pilot initially intended to return to the departure airport but subsequently elected to perform a precautionary landing. As the pilot brought the aircraft into a hover, the helicopter rotated toward the left nose. Following the landing, the pilot shut down the engine and discovered that the vertical fin and the tail rotor gearbox had separated from the aircraft.
The investigation
Investigators identified that one of the tail rotor pitch link control rods had failed. A metallurgical examination of the failed components revealed evidence of fatigue on the failed tail rotor pitch link control rod.
Findings
- The manufacturer specified an after last flight of the day (ALF) inspection, which was designed as a detailed inspection capable of being performed by either maintenance personnel or pilots.
- The operator's Director of Maintenance reported that pilots were responsible for performing all daily checks.
- The pilot had not received training to conduct the ALF inspection.
- The FAA check airman responsible for the pilot's initial FAR 135 checkride was unaware of the specific requirements of the ALF inspection.
- The checklist located inside the helicopter had not been updated to include the most recent and detailed version of the ALF inspection instructions.