Piper PA18 N2684A accident near Newman Lake, Washington

Probable cause

A partial loss of engine power for reasons that could not be determined because postaccident examination of the engine did not reveal any anomalies that would have precluded normal operation.

NTSB analysis

The private pilot performed two low passes to the snow-covered airstrip, during which the airplane's flaps were extended and carburetor heat was on. After completing the second low pass, the pilot retracted the wing flaps, turned off the carburetor heat, and applied engine power to go around. The engine subsequently experienced roughness and a partial loss of power. The pilot turned the carburetor heat back on, but engine power was not restored. Unable to maintain altitude, the pilot elected to land on the airstrip he had been overflying. During the landing, the airplane nosed over due to the depth of the accumulated snow, which resulted in substantial damage.

A postaccident examination of the carburetor revealed full control continuity to the carburetor heat/air box, the butterfly valve reached full travel, and full control continuity from the cockpit throttle and mixture controls to the carburetor was confirmed. An engine run revealed no anomalies. Although the airplane was operating in conditions that were conducive to a serious risk of carburetor ice accumulation at a descent power setting, the engine was operating at a takeoff/go-around power setting at the time of the loss of power, and it is unlikely that carburetor ice would have accumulated during this time. Therefore, the reason for the partial loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for WPR16LA045 for the full record.