Piper PA-12 N7878M accident near Cumberland, Wisconsin

Probable cause

The total loss of engine power due to carburetor icing and the pilot’s delayed use carburetor heat in weather conditions conducive to carburetor icing.

NTSB analysis

The pilot was conducting a personal flight when during cruise descent the engine began to sputter and suddenly lost power. He moved the throttle to full-forward and increased the mixture to full-rich, but the engine resumed operation only 5 to 10 seconds before it lost power a second time. The pilot reported that the airplane was at low altitude that required an immediate forced landing into a nearby cornfield. The airplane sustained substantial damage to the engine mounts, fuselage structure, and right wing.

Examination of the airplane fuel system and the engine revealed no evidence of a preimpact mechanical malfunction. There was ample fuel recovered from the fuel tanks at the accident site, and there was no evidence of any water or particulate contamination of the fuel system.

The weather conditions at the time of the accident were in the range of susceptibility for the formation of serious carburetor icing at glide engine power. According to a Federal Aviation Administration Special Airworthiness Information Bulletin, pilots should use carburetor heat while in weather conditions where carburetor icing is probable. When interviewed, the pilot acknowledged that he did not review a carburetor icing chart before the flight. However, he stipulated that he applied carburetor heat after the engine began sputtering.

Based on the available information, the loss of engine power was likely due to carburetor ice accumulation. Additionally, the low altitude at which the loss of engine power occurred significantly reduced the amount of time available to the pilot to troubleshoot and restore engine power before the forced landing.

Text from the NTSB. Open the NTSB docket for CEN24LA356 for the full record.