Incident Overview
During a descent for landing, a pilot detected a loss of engine power. The pilot applied carburetor heat, which appeared to correct the power loss. However, after a short period, the pilot discontinued the carburetor heat. Subsequently, on final approach at approximately 500 feet above ground level (AGL), the engine failed.
Supporting Evidence
An icing probability chart indicated that the existing atmospheric conditions were conducive to carburetor icing. Additionally, examination of the spark plugs revealed evidence of an over-rich fuel mixture. When the engine was removed and installed on another aircraft, it operated without any problems.
Operational Context
The pilot reported the sequence of events: initial power loss during descent, temporary correction with carburetor heat, discontinuation of heat, and eventual engine failure on final approach. The conditions at the time, as indicated by the icing probability chart, were favorable for the formation of carburetor ice. The spark plug condition suggested an overly rich mixture, which can be consistent with carburetor icing effects.
Conclusion
The investigation noted that the engine ran normally when tested on a different aircraft, indicating that the failure was likely related to the specific conditions during the flight rather than a mechanical defect. The pilot's actions and the environmental factors were documented, but no causal determination was made in the source material.