What happened
The pilot was conducting a low-level inspection of a herd of cattle when he noticed what appeared to be a mechanical issue with the helicopter's engine and main rotor system. Believing an emergency descent was necessary, he initiated an autorotation. However, during this maneuver, the aircraft lost directional control due to a failure in the tail rotor system. The helicopter entered an uncontrolled left spin that continued until it impacted the ground.
The investigation
Post-accident examination of the wreckage revealed that the primary cause of the loss of control was an in-flight separation of the tail rotor assembly. This separation occurred because the tail boom had shifted significantly from its normal position. Further analysis identified the root mechanical failure as a fracture and subsequent failure of the left boom support tube fitting, which compromised the structural integrity of the tail section.
Findings
The investigation determined that the sequence of events was initiated by the pilot's perception of an engine or rotor problem, leading to the autorotation. The critical factor in the accident was the structural failure of the left boom support tube fitting. This failure allowed the tail boom to shift, resulting in the loss of the tail rotor and subsequent control of the aircraft during the emergency descent.