Incident Overview
A pilot reported that during an en route descent, carburetor heat was applied and then turned off. After continuing the descent and reducing power, the pilot turned the carburetor heat on again, at which point the engine ceased operation. Attempts to restart the engine were unsuccessful, and the airplane subsequently collided with a sewage treatment dike during the ensuing forced landing.
Sequence of Events
The pilot initiated a descent from 4,500 feet above ground level (AGL) and initially turned the carburetor heat on before turning it back off. The descent continued to 2,000 feet AGL, where the pilot reduced power and once again activated the carburetor heat. Immediately thereafter, the engine quit.
Carburetor Icing Considerations
A review of the probability carburetor icing chart indicated that, based on the weather conditions present at the time of the accident, the engine could encounter serious icing at glide power settings. This condition is known to affect engine performance.
Forced Landing and Impact
Unable to restart the engine, the pilot performed a forced landing. During this maneuver, the airplane struck a sewage treatment dike, resulting in the accident.