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NTSB investigation record

ANC12CA072

Completed

Piper Pa-12· N7779H

Date
July 6, 2012
Location
Quinhagak, AK
Conditions
VMC
Record
Published September 25, 2020

Primary finding

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.

Investigator assessment

Analysis narrative

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.

Source record

Factual narrative

In a telephone conversation with the National Transportations Safety Board (NTSB) investigator-in-charge just after the accident, 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 he was unable to clear terrain at the departure end of the site, about 400 feet from where he aborted the landing. The airplane impacted terrain, 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 he did not realize it, or take any corrective action for application of carburetor heat. In a telephone conversation on August 23, he said 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, reported by the pilot, could expect serious carburetor icing while at cruise power.

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