Incident Overview
During a night flight in a snowstorm, the pilot of an air ambulance reported 'a bit of a problem' with the right engine and feathered the right propeller. He attempted to divert to the nearest suitable airport but, after receiving the latest weather report, elected to return to base. While making a left turn, the airplane reentered instrument meteorological conditions (IMC) and impacted a mountainside on a magnetic heading of 092°. The heading to the airport of intended landing was 272°. All five occupants survived and were rescued the following afternoon.
Investigation Findings
Examination of the right engine fuel control revealed thick grease on the camshaft, which prevented a spring from returning the 3d cam to a lower altitude position. The cam was stuck at a position corresponding to an altitude of approximately 15,000 feet. The fuel flow schedule for flight idle was below specifications. Additionally, shroud material was found delaminated from the left engine second stage compressor housing.
Probable Cause
The official probable cause was a malfunction of the right engine fuel control that caused the engine to flame out, and delamination of the left engine compressor shroud. Contributing factors were the pilot becoming disoriented, mountainous terrain, dark night conditions, and adverse weather.