What happened
While operating at 9500 feet, the pilot was engaged in approximately 20 minutes of level flight when the engine power decreased to below idle rpm. Prior to this loss of power, the fuel flow had been steady at 13 gallons per following hour (gph). Following the power loss, the fuel flow increased to 28 gph. The outside air temperature at the time was -20 degrees Celsius.
The pilot attempted several measures to restore engine power, including the application of carburetor heat, but these efforts were unsuccessful. Consequently, the pilot performed a forced landing in a field. The pilot was not injured during the event.
The investigation
Following the landing, the pilot, who is an aircraft mechanic, conducted an inspection of the engine. During this post-landing examination, no mechanical discrepancies were identified. The pilot reported that upon restarting the engine after the inspection, it functioned normally.