Cessna 172 N7267A accident near Palmer, Alaska

Probable cause

The pilot's delayed application of carburetor heat in weather conditions conducive to carburetor icing, which resulted in a partial loss of engine power, a precautionary landing, and impact with terrain.

NTSB analysis

The pilot reported that, about 15 minutes after departure, the engine began to run rough and experienced a partial loss of power. He provided conflicting statements about the phase of flight when this occurred; he was either in cruise flight or was flying at a reduced power setting during a low approach to a remote site. After completing emergency engine procedures, which included applying carburetor heat, the pilot was unable to restore engine power and selected an all-terrain vehicle trail as a forced landing site. Just before touchdown, when the airplane was about 15 ft above the ground, the left wing struck a tree, and the airplane yawed left and touched down in a nose-low, off-center angle. The airplane sustained substantial damage to both wings and the fuselage.

Postaccident examination of the engine, including a test run, revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation.

Weather conditions about 15 nautical miles from the accident site were conducive for carburetor icing at cruise power and serious icing at glide power. The pilot only reported applying carburetor heat to restore engine power. Therefore, it is likely that carburetor ice accumulated before he applied the heat, which resulted in a partial loss of engine power. Further, the delayed application of carburetor heat was insufficient to melt the ice and restore power.

Text from the NTSB. Open the NTSB docket for ANC20LA002 for the full record.