Event Description
A helicopter was performing external load operations, during which the pilot reported a flickering fuel light while moving a heavy load. The helicopter later lost engine power while hovering out of ground effect. After moving two or three loads, the pilot felt the engine surge slightly, though all engine instruments appeared within normal ranges. The pilot elected to continue moving the external load, but the engine then cut back to ground idle, causing the helicopter to descend through trees.
Maintenance Actions
Following the initial fuel light indication, the company's mechanic drained the fuel tank, purged the fuel lines, and replaced the fuel filter. The helicopter was then filled with what was described as "clean fuel" and test flown for approximately 30 minutes with no problems noted. After the engine power loss incident, the engine was removed from the airframe and shipped to an engine overhaul facility for further investigation.
Engine Examination
An initial examination of the engine at the overhaul facility did not reveal any pre-impact anomalies. The engine was placed in a test cell for a full run-up. Two engine starts were attempted, but the engine failed to start. After the first attempt, the idling device strainer was found clogged and was replaced. Following the second failed attempt, the engine was disassembled. Examination revealed that the fuel tube was clogged, preventing fuel from reaching the fuel injection wheel. Fuel samples taken at the accident scene and during the engine examination did not contain contaminants. A lab test of the substance found in the fuel tube failed to identify the foreign substance.