On December 8, 2003, a Hughes 369D (registration N8343F) was involved in an aviation accident near Moclips, WA. Investigators recorded the probable cause as: A sudden loss of engine power during hover for undetermined reasons. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter lost engine power during long-line timber operations; the pilot autorotated to a forced landing, resulting in substantial damage to the fuselage and tail boom. Post-accident examination found carbon deposits consistent with coked oil in the turbine.
Incident Summary
A helicopter experienced a loss of engine power while the pilot was conducting long-line operations in support of a timber sale. Following the power loss, the pilot performed an autorotation and completed a forced landing near the base of operations. During the landing, the helicopter sustained substantial damage to the fuselage and tail boom assembly.
Post-Accident Examination
Post-accident examination of the engine assembly revealed heavy black carbon-like deposits throughout the turbine section. Extensive thermal damage, including metal splatter, was noted on the first and second stage turbine wheels and nozzles. A number of the turbine blade ends were melted away.
Findings
Samples of the black carbon-like deposits were taken from different locations throughout the turbine assembly and analyzed using semi-quantitative X-ray energy dispersive analysis. The analysis concluded that the deposits were consistent with coked oil. No presence of jet fuel was found in the oil deposits. The origin of the oil could not be determined.