Piper PA-12 N7779H accident near Quinhagak, 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 stated that he was landing his tailwheel-equipped airplane at an off-airport site. During the landing roll, he aborted the landing but was unable to clear terrain at the departure end of the site, about 400 feet from where he aborted the landing. The airplane impacted the ground, sustaining substantial damage to both wings and the fuselage. The pilot indicated that there were no preaccident mechanical anomalies with the airplane that would have precluded normal operation.

In his written statement to the NTSB, the pilot stated that the engine may not have been producing full power but, if so, he did not realize it or take any corrective action, such as applying carburetor heat. In a telephone conversation, he said that he had been flying at reduced power settings during his reconnaissance passes, with occasional use of carburetor heat to clear any possible carburetor ice. He also stated that his normal before-landing procedure is to turn off the carburetor heat on short final. According to a carburetor icing probability chart, an airplane operating in the ambient conditions at the accident site, as reported by the pilot, could expect a serious risk of carburetor icing while at cruise power.

Text from the NTSB. Open the NTSB docket for ANC12CA072 for the full record.