AAIB investigation to Bell 407, N120HH
Bell 407 (N120HH), Engine failure and autorotation, Long Marston, Warwick-shire, 24 June 2020.
Summary:
The pilot and passenger were returning to Thruxton Aerodrome following a short flight over the Malvern hills when the engine failed. The pilot executed an autorotation landing in a field near Long Marston, after which they were both able to exit the helicopter without injury. However, the tail boom was severed during the landing and the helicopter was destroyed by fire.
The investigation found that the engine suffered an uncontained failure of the gas producing turbine disc due to insufficient oil reaching the bearings as a result of an oil leak. Due to the extensive damage to the helicopter it was not possible to determine the cause of the oil leak.
Two Safety Recommendations were made regarding the Failure Mode and Effects Analysis for the engine, and the fire resistance and crashworthiness of aircraft components. The helicopter manufacturer undertook two Safety Actions regarding advice to pilots, and one Safety Action regarding analysis of the airframe fuel filter.
Download report:
Safety Recommendation Document