Accident Sequence
About four minutes after takeoff, while the helicopter was maneuvering at an altitude between 400 and 500 feet above ground level, the Engine Power Out (EPO) warning light and horn activated. The pilot reduced collective control and initiated an autorotation. To avoid trees, the pilot executed a downwind turn. During the descent, the engine N2 (power turbine) RPM stabilized at 88 to 90 percent, compared to the normal operating range of 102 to 103 percent. The helicopter touched down in a soft field at a forward speed of 20 to 25 MPH, slid approximately 30 feet, and rolled onto its side.
Investigation Findings
On-site investigators discovered that the adjustable governor lever control rod was disconnected from the governor control lever. According to a McDonnell Douglas investigator, this disconnection would result in a loss of automatic governing of engine RPM. The nut and washer used to secure the adjustable control rod to the governor control lever were found in the bottom of the engine compartment. However, the cotter pin specified for safetying the nut and washer was not located.
Operational Context
The engine fuel governor had been replaced since the previous flight. The aircraft operating handbook directed pilots to check the fuel control and N2 governor linkages during the preflight inspection.