What happened
The pilot was conducting an approach toward a designated landing platform when the aircraft suddenly experienced a loud bang. In response to this mechanical event, the pilot initiated an emergency autorotation maneuver directly into the adjacent water. During the descent, the helicopter rolled inverted and subsequently struck the landing platform. The force of the waves battering the airframe against the structure caused extensive damage to the aircraft.
The investigation
Following the accident, investigators conducted a teardown examination of the aircraft's engine to determine the root cause of the failure. The inspection revealed that the first stage turbine wheel, identified by part number 6895801G, had failed catastrophically and exited the engine case. Metallurgical analysis indicated that the wheel failed due to low cycle thermal fatigue, with the fracture originating in the rim area of the component.
Findings
The primary factor contributing to the accident was the engine failure caused by the turbine wheel separation. This mechanical breakdown necessitated an emergency water landing, which resulted in significant structural damage to the helicopter due to the impact with the platform and subsequent wave action.