Aviation accident SEA06LA065

The pilot's failure to identify the overspeed of the helicopter's main rotors due to a turbine governor malfunction, and his failure to take the appropriate actions described in the Flight Manual's emergency procedures section. Factors include the malfunction (partial bypass) of a lubricating system filter screen, which led to the partial blockage of an oil supply orifice, resulting in the failure of the splines on the power turbine governor speed input shaft, and ultimately to the loss of the governor's ability to correctly control fuel input to the engine. Additional factors include no suitable landing terrain and tree stumps in the area the pilot elected to land in.