The pilot conducted a preflight inspection that included procedures to ensure removal of accumulated water before flight. Due to the cold temperature, the pilot requested an engine pre-heat service, which was applied for an estimated 15 minutes. There were no abnormalities during the engine start, taxi, and engine run-up before takeoff. During the takeoff climb, the engine sustained a partial loss of power; the pilot applied carburetor heat and elected to return to the departure airport. While returning to the airport, the airplane entered an aerodynamic stall, impacting the ground adjacent the runway. A postaccident examination did not reveal any discrepancies that would have prevented normal operation of the airplane or its systems.

A postaccident examination revealed a chunk of ice with debris frozen in the gascolator fuel bowl; however, the ice chunk was not large enough to block the fuel flow to the engine. Further examination revealed no water in the carburetor. The closest official weather observation station, about 14 miles west of the accident site, reported the temperature as 4 degrees Celsius (C) and the dew point as minus 1 degrees C about 35 minutes after the accident. Based on the ambient temperature and the dew point, serious carburetor icing conditions were possible at cruise power. The airplane’s Pilot Operating Handbook (POH), in the cold weather operation section, states that “appropriate use of carburetor heat is recommended; full carburetor heat may be required for temperatures below -12 Celsius whereas partial heat could be used in temperatures between 4 and -12 degrees Celsius…Use the minimum carburetor heat required for smooth operation in take-off, climb, and cruise.” The investigation determined that the pilot's application of carburetor heat, while consistent with guidance in the POH, was still inadequate to prevent carburetor icing.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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