What happened
The flight was proceeding at cruise power settings when the aircraft was established at 3,000 feet mean sea level. The duration of this cruise phase was approximately 1.1 hours. During this segment, the pilot experienced an unexpected loss of engine power.
In response to the power failure, the pilot immediately pushed the mixture control fully in and applied carburetor heat. These standard procedures for addressing potential fuel flow issues or icing were executed promptly. However, engine power was not restored despite these efforts.
Consequently, the pilot initiated a forced landing procedure. The aircraft landed in a field characterized by rough and uneven terrain. During the landing roll, the airplane struck fences and posts located within the field.
Findings
Meteorological conditions at the time of the incident included an air temperature of 80 degrees Fahrenheit and a dew point of 60 degrees Fahrenheit. Analysis of the icing probability chart indicates that moderate icing conditions were present at cruise power settings under these atmospheric parameters.
The sequence of events suggests that carburetor icing was the primary factor contributing to the loss of engine power. The combination of temperature, humidity, and power setting created an environment conducive to ice formation within the carburetor, which restricted fuel-air flow and could not be cleared by the application of heat.
Safety message
This incident highlights the risk of carburetor icing even at relatively high temperatures when the dew point is sufficiently close to the air temperature. Pilots operating aircraft with carburetors should remain vigilant for icing conditions during cruise flight, particularly when using cruise power settings that lower manifold pressure and increase airflow velocity through the carburetor venturi.