What happened
The aircraft was operating as an aerial applicator when it experienced an unexpected loss of engine power. At the time of the incident, the pilot was executing a turn to enter a field for a swath run. Following the power failure, the pilot initiated a forced landing on a narrow road. During the landing roll, the aircraft struck a pile of rocks.
The investigation
An FAA airworthiness inspector examined the engine after the accident and found no anomalies that would explain the loss of power. Weather data indicated a temperature of 73 degrees Fahrenheit with a dew point of 53 degrees. These atmospheric conditions were identified as being within the range conducive to carburetor icing.
Findings
The investigation determined that the carburetor heat control was in the 'off' position at the time of the incident. The combination of the specific temperature and dew point, along with the use of cold air from the carburetor, likely resulted in ice formation within the carburetor, leading to the engine failure.
Safety message
Pilots operating aircraft with carbureted engines should be vigilant for conditions conducive to icing. Carburetor heat should be used as required by the manufacturer's guidelines, even when visible moisture is not present, to prevent power loss due to ice accumulation.