Incident Overview
A Cessna 172H, equipped with a carburetor, was flying approximately 9 nautical miles west of its first fuel stop. The pilot began a letdown through a hole in a broken cloud layer.
Weather Conditions
The surface weather observation at the intended destination, recorded several minutes after the accident, reported two broken cloud layers at 2,600 feet and 3,400 feet, with an overcast layer at 7,000 feet. The temperature was 53 degrees Fahrenheit, and the dew point was 45 degrees Fahrenheit.
Sequence of Events
The pilot reported applying carburetor heat and reducing engine RPM. Subsequently, he had to descend faster and reduce engine RPM further. He continued a gliding descent to 4,000 feet and then attempted to reapply power with no effect.
Forced Landing
A forced landing was executed to a muddy, wet agricultural field. During the landing, the nose gear collapsed, and the aircraft nosed over.
Advisory Guidance
FAA Advisory Circular 61-23B, "Pilot's Handbook of Aeronautical Knowledge," provides guidance for operations in carburetor icing conditions. It states that carburetor heat should be turned to full-on before closing the throttle and left on during closed-throttle operation. It also advises that the throttle should be opened smoothly for a few seconds periodically to keep the engine warm, as the carburetor heater may not provide enough heat to prevent icing.