What happened
The incident occurred during a maintenance test flight involving a helicopter. The pilot elected to perform a practice autorotation maneuver as part of the operational check. During this specific phase of the flight, the engine experienced a complete loss of power.
Following the power failure, the helicopter impacted the ground with significant force. The hard landing caused the main rotor blades to strike the tail boom. This impact resulted in the separation of the tail boom from the fuselage.
The investigation
Post-incident analysis included a test run performed on the engine to determine the cause of the power loss. The mechanical evaluation revealed no discrepancies in the engine's operation or condition during the test.
Findings
The sequence of events was initiated by the pilot's decision to conduct a practice autorotation. The subsequent complete loss of engine power led to the hard impact with the ground. The structural damage, specifically the separation of the tail boom, was a direct result of the main rotor blades striking the boom upon impact.