What happened
During cruise flight at approximately 300 feet above ground level, the pilot reported hearing a loud noise followed by an immediate loss of engine power. Despite the sudden mechanical failure, the pilot maintained control of the aircraft and executed a controlled autorotation. The helicopter was set down safely on the ground with no further incident or damage to the airframe beyond the engine compartment.
The investigation
A subsequent inspection of the engine revealed that the number 6 cylinder connecting rod had failed near the wrist pin. Metallurgical analysis confirmed that the failure originated from a fatigue fracture within the metal structure of the connecting rod. This internal structural failure severed the mechanical link necessary to transfer power, resulting in the total loss of engine function.
Findings
The primary factor contributing to the event was the fatigue fracture of the number 6 cylinder connecting rod. The pilot's ability to recognize the failure and execute a proper autorotation allowed for a safe landing despite the catastrophic engine failure. No other mechanical anomalies were reported that would have contributed to the loss of power.
Safety message
Regular inspection of engine components, particularly those subject to high cyclic stress such as connecting rods, is critical for preventing in-flight power loss. Pilots must remain proficient in autorotation techniques to ensure safe outcomes when unexpected engine failures occur.