Incident Overview
During descent approximately three nautical miles from the airport, the pilot observed a drop in engine rpm to about 1000. Attempts to restore engine power within 30 seconds were unsuccessful, and the engine ceased operation entirely.
Examination Findings
Post-incident examination of the aircraft revealed fuel present in the carburetor bowl and in the fuel line between the fuel pump and the gascolator. The engine was examined and test-run, showing no evidence of mechanical malfunction.
Icing Probability Analysis
Review of published induction system icing probability data for the temperature and dew point reported at the time of the incident indicated that conditions fell within the "visible icing at rated power" and "serious icing at glide power" categories. The data charts note that icing conditions within the limits of the "visible icing" curves may become "serious" after 15 minutes of continuous operation in such conditions.
Relevant Checklist Information
According to the Cessna Owner's Manual for the Model 177, the "Let-Down" checklist includes: (1) Mixture – Rich. (2) Power – As desired. (3) Carburetor Heat – As required to prevent carburetor icing.