Cessna 180 N6414X accident near Cottonwood, California

Probable cause

A partial loss of engine power due to carburetor icing as a result of the pilot's failure to apply carburetor heat during a reduced-power approach descent.

NTSB analysis

The pilot was approaching the destination airport at an altitude of about 1,500 ft about 1.5 miles from the runway threshold, when he attempted to add power by advancing the throttle, but "nothing happened." He "cycled" the mixture and the magnetos, but there was no change, and the airplane descended below the desired glidepath. The pilot did not use carburetor heat during the approach, and he did not apply it following the engine’s failure to respond to the advanced throttle setting. The pilot chose to conduct an off-airport landing in a field, during which the airplane stalled while the pilot attempted to maneuver over power lines.

There was no evidence of any fuel or oil leaks, thermal or fire damage, or any nonimpact-related deficiencies or damage. During a test run, the engine started and functioned normally, except that the maximum rpm achieved was slightly below the design specification. The examination and testing did not reveal any mechanical reasons for the power loss reported by the pilot.

The ambient temperature and dew point in the area of the accident site about the time of the accident were conducive to the development of carburetor icing. Given the lack of mechanical anomalies and the pilot's failure to apply carburetor heat during the descent and following the engine’s lack of response to the power increase, it is likely that the engine developed carburetor ice during the approach at the reduced throttle setting, which resulted in the engine's failure to respond to the pilot's throttle change. The pilot's failure to apply carburetor heat during the reduced power descent was contrary to the airplane manufacturer's Owner's Manual guidance.

Text from the NTSB. Open the NTSB docket for WPR19LA017 for the full record.