Incident
A Bell 206B helicopter experienced a loss of engine power during a practice hover in preparation for an external load operation. The aircraft was hovering at approximately 100 feet above ground level (AGL) with a 100-foot cable attached.
Sequence of Events
While hovering, the fuel boost pump light illuminated and the boost pump pressure dropped to zero. The pilot initiated a descent, but while still at about 100 feet AGL, the engine lost all power. The pilot executed an autorotation, but the aircraft landed hard.
Post-accident inspection revealed frost on the fuel cap that was not present during the preflight inspection. Approximately 45 minutes after the accident, a small amount of ice was observed floating in the fuel. Subsequent examination of the engine and aircraft found water in the fuel tank, airframe fuel filter, engine fuel pump filter, and high pressure fuel filter. The fuel supply line from the high pressure fuel filter to the fuel control unit was empty.
Findings
The helicopter was a Bell 206B, which was equipped with an airframe fuel filter. Anti-ice fuel additive was not required for this model due to the presence of the filter. The source of the water and ice contamination could not be determined. The ambient temperature was minus 1 degree Fahrenheit.