Incident Overview
A pilot reported that while cruising at approximately 1,000 feet above ground level with a low power setting for about 45 minutes, the sky was clear but fog was present in the valleys. Upon adding power to climb, the engine became rough. The pilot attempted to remedy the situation by applying carburetor heat and switching fuel tanks, but these actions did not correct the roughness. Leaning the mixture smoothed the engine operation, yet it continued to lose power.
Forced Landing
Recognizing that the power loss would not allow continued flight, the pilot set up for a forced landing on a frozen reservoir. At touchdown, the main landing gear dug into the snow, causing the airplane to nose over.
Post-Accident Engine Run
After the accident, the engine was run satisfactorily, indicating no mechanical failure was found. The precise cause of the in-flight power loss was not determined.