What happened
During an attempted takeoff, the engine of the aircraft lost power, causing the helicopter to experience a hard landing. Prior to this flight, the engine's adjusted valve assembly had been removed and replaced. Following that maintenance work, the pilot flew the helicopter to a hospital to pick up a flight paramedic and a nurse. As the aircraft attempted to lift off with the additional passengers, the engine power failed, leading to the impact.
The investigation
A post-accident test run and examination of the engine revealed that uncommanded engine shutdowns occurred when operating at higher power settings. Upon disassembly of the adjusted valve assembly, investigators discovered that the stop electro valve was damaged internally. Specifically, there was a deformation in the core housing that prevented the stop electro valve from opening completely during operation.
This mechanical failure caused a pressure drop, which triggered the untimely activation of the stop purge valve and a subsequent drop in fuel flow. The adjusted valve assembly had been overhauled by the engine manufacturer and sold to the operator before being installed on the engine. While the manufacturer stated that the damage occurred between the time the component was shipped from the factory and its first use, they could not determine exactly how the damage happened. Metallurgical examination confirmed that the damage occurred while the valve was in a disassembled state.