What happened
Approximately one and a half minutes after takeoff, the pilot heard a loud bang followed by significant vertical and lateral vibration. The helicopter began to descend, pitch forward, and roll to the right as the vibration intensified. Recognizing the severity of the situation, the pilot elected to perform an autorotative landing on a nearby sand bar. Upon touching down on sloping terrain, the aircraft rolled over onto its right side, sustaining substantial damage.
The investigation
During the post-accident examination, the transmission and engine were disassembled for inspection. No discrepancies were found in these components. However, it was determined that one of the main rotor blade caps had separated from the blade. Unfortunately, the cap itself was not recovered during the search.
Findings
The investigation could not determine whether the blade cap separation occurred before or after the impact with the ground. The sequence of events suggests a mechanical failure in the rotor system initiated the emergency descent.