Flight Details
Airspur Flight 500, a domestic cargo flight, departed Kalispell, Montana, at 1903 Mountain Daylight Time (MDT) with an instrument flight rules (IFR) flight plan to Great Falls, Montana.
Emergency Situation
At 1922 MDT, the pilot notified Salt Lake Air Route Traffic Control Center (ARTCC) that he was returning to Kalispell due to a rough running engine. Shortly thereafter, the pilot reported that the engine had failed completely.
Forced Landing
The pilot executed an emergency forced landing on a mountain ridge at approximately 5,500 feet elevation in instrument meteorological conditions (IMC). The accident site was approximately 18 nautical miles east of Kalispell.
Investigation Findings
Subsequent disassembly of the engine revealed that the number four connecting rod had failed catastrophically.