Incident Overview
On an unspecified date, a pilot purchased 36 gallons of avgas at 1813 hours and departed the airport approximately 1830. Around 1850, while in cruise flight, the engine sputtered, ran rough, and then quit. During the subsequent descent, severe turbulence was encountered, and the airplane possibly entered a spin. The pilot sighted a clearing and executed a forced landing in deep snow, at night.
Post-Accident Examination
Upon inspection of the accident site, there was no odor of fuel or evidence of fuel stains. When the airplane was removed, approximately two to three gallons of fuel leaked onto the floor of the transport trailer. At the salvage yard, water was used to fill both fuel tanks. Neither integral fuel tank was breached. The fuel vent lines, check valve, fuel selector valve, fuel supply lines, and auxiliary fuel pump were found to be unremarkable. The gascolator was not damaged and contained no fuel; the fuel screen was clean and free of debris. No fuel stains were present anywhere on the airframe. About two ounces of residual fuel were drained from the carburetor.
Engine and Fuel System Analysis
According to the engine manufacturer's investigator, the spark plugs and exhaust system gas path exhibited dark black coloration, consistent with engine operation at a rich fuel/air mixture. No mechanical anomalies were noted in the fuel system components examined.
Weather Conditions
Weather recorded at a remote station near the accident site indicated the following: temperature 23°F, dew point 16°F, relative humidity 74%, wind from 070° at 6 miles per hour gusting to 10 miles per hour. According to the Icing Probability Chart, these conditions were conducive for the formation of carburetor ice in glide and cruise power configurations.