What happened
While climbing through 5,000 feet above sea level, a Eurocopter Lama SA 315B helicopter, registration C-FJJW, experienced a significant drop in engine power. The pilot, accompanied by two passengers, was attempting to return to a service landing area when the rotor RPM began to decay rapidly. In an attempt to land on the shore of a frozen Downton Lake, the pilot performed a forced landing without entering autorotation. During the maneuver to arrest forward speed, the tail boom struck the ground and separated from the main fuselage. The aircraft rolled end-over-end, resulting in the engine separating from the airframe and a breach of the fuel reservoir. While no fire occurred, the passenger in the left forward seat sustained a punctured lung, while the pilot and the second passenger escaped with minor injuries.
The investigation
Investigators examined the engine and fuel systems to determine the cause of the power loss. Analysis of the engine's fuel injection tube and wheel assembly revealed significant deposits of a polymer-type substance. Laboratory testing identified these deposits as an amino composite, a material consistent with the water-absorbing media found in certain fuel filters. Further investigation into the refueling equipment revealed that the gear used at the time contained a polyacrylate-based material designed to absorb water.
Evidence suggested that because the refueling gear was near water saturation, the differential pressure caused the water-absorbing media to migrate out of the filter and into the fuel supply. This material subsequently obstructed the fuel passages to the engine's combustion section. The investigation also noted that the pilot had observed engine lagging during a previous flight, but the issue was not identified as a critical failure. Additionally, it was noted that the occupants in the forward cabin were not wearing their available shoulder harnesses, a factor that likely contributed to the severity of the injuries sustained.