Accident Overview
During an external load operation, the helicopter's engine stopped producing power. The pilot executed an autorotation into a river bed area. During the landing, the helicopter contacted a boulder and rolled over.
Investigation and Examination
Engine examination revealed a collapsed fuel inlet screen within the fuel nozzle, which restricted fuel flow. Heavy contamination was noted on the screen. Subsequent analysis identified the contaminant as a sodium-rich silicon material.
Wash Procedure and Contamination
The helicopter was operated exclusively in a marine environment. The operator performed a daily compressor wash procedure in accordance with the engine manufacturer's service letter. The specified procedure resulted in immersion of the fuel nozzle in sodium-contaminated wash water, with subsequent infiltration of the solution into the fuel nozzle inlet screen.
Fuel Nozzle Screen Details
The fuel nozzle inlet screen has a life limit of 2,500 hours and is not subject to any routine inspection requirements.