Accident Sequence
While cruising at approximately 600 feet above ground level (AGL), the helicopter experienced an engine failure. The pilot executed a forced landing, during which the main rotor blades collided with trees.
Fuel System Examination
Post-accident examination of the aircraft's fuel system focused on the check valves located in the fuel lines that transfer fuel from the forward fuel cell to the aft fuel cell. These check valves were found to be worn, and one of them was stuck in the closed position.
Further inspection of the fuel manifold, which contains two additional poppet valves, revealed that one of the poppet particles was present in all of these check valves. The source notes that with both poppet valves closed, the fuel boost pumps cannot supply pressure to the single fuel line, the fuel pressure transducer, or the engine.
The findings indicate a mechanical issue within the fuel system, but no probable cause has been stated in the source material.