Cessna 150 N22197 accident near St. Agatha, Maine

Probable cause

A partial loss of engine power due to carburetor ice as a result of the pilot’s delayed use of carburetor heat while operating in environmental conditions conducive to serious carburetor icing.

NTSB analysis

About 15 minutes into the flight, while flying at 2,500 ft mean sea level (msl), the airplane encountered environmental conditions that were favorable for the formation of serious carburetor ice at cruise engine power settings. The flight continued and the pilot noted that the engine’s output dropped from about 2,300 rpm to about 1,500 rpm. He applied carburetor heat and left it applied, cycled the fuel shutoff valve, pumped the throttle, and checked the ignition switch, but those efforts did not restore power. After descending to 2,000 ft msl, he turned to return to the departure airport but performed a forced landing in a field after recognizing the flight was unable to reach the departure airport. The nose landing gear collapsed during the landing roll after encountering a furrow, resulting in substantial damage to the engine mount and right wing. Postaccident examination of the engine and its systems revealed no evidence of preimpact failure or malfunction.

A High Resolution Rapid Refresh (HRRR) model sounding created for the approximate time and location where the pilot reported the airplane began descending consistent with the reported loss of engine power revealed that the temperature and dew point were 34.5° F and 33.8° F, respectively. The values were close to 100% relative humidity.

Thus, it is likely that during cruise flight carburetor ice formed and subsequently resulted in the reported loss of engine power. The pilot’s delayed application of carburetor heat during the cruise portion of the flight while operating in environmental conditions favorable for serious carburetor ice at cruise power allowed for the formation of carburetor ice.

Text from the NTSB. Open the NTSB docket for ERA25LA028 for the full record.