Piper PA-18-150 N8899Y accident near Palmer, Alaska

Probable cause

The pilot's failure to use continuous carburetor heat while operating in conditions conducive to carburetor icing, which resulted in the development of carburetor ice and a subsequent partial loss of engine power.

NTSB analysis

The pilot reported that while in level cruise flight, the engine began to run rough and lost power. Unable to restore full engine power, the pilot selected an area of snow-covered terrain as a forced landing site. During the landing, as the main wheels contacted deep snow, the airplane nosed over, sustaining substantial damage to the right wing lift strut.

The pilot reported that he applied carburetor heat after the initial loss of engine power and that the engine was only able to maintain 1,100 rpm. About the time of the accident, a weather observation station located about 25 miles northwest of the accident site reported the temperature at 45 degrees F and dew point at 41 degrees F. According to a carburetor icing probability chart, the airplane was susceptible to icing at both cruise and climb power. The pilot did not report and a postaccident examination of the wreckage did not reveal any evidence of a mechanical malfunction. It is likely that the loss of engine power was due to carburetor icing.

Text from the NTSB. Open the NTSB docket for ANC13CA044 for the full record.