Preflight Inspection and Takeoff
Before the flight, the copilot began a preflight inspection. The helicopter was subsequently moved from the hangar to the terminal, where a witness observed the engine cowling open. The pilot also conducted a walkaround visual inspection before flight. Neither crew member noted any discrepancies.
In-Flight Anomaly
Approximately 1 minute and 40 seconds after takeoff, the flight crew heard a noise, followed by a loss of directional control. Three passengers noted the odor of something overheating. The crew performed an autorotation and landed on hilly terrain. The helicopter came to rest against a tree in a ravine.
Post-Incident Examination
During an examination of the helicopter, the two left-side engine cowling latches were found open. Additionally, the left side of the aft engine cowling was open. Evidence showed that during the flight, the left side of the cowling contacted the main rotor blades. The cowling then made contact with Section II of the tail rotor driveshaft. Friction between the cowling and the driveshaft resulted in localized high temperature, and the tail rotor shaft failed at that location. One of the four tail rotor blades separated during the occurrence.