Accident
On January 1, 2016, at about 1530 Pacific standard time, a Piper PA-18-150, registration N2684A, was substantially damaged during a precautionary landing to a private dirt airstrip near Newman Lake, Washington. The private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed for the local flight, which was conducted under 14 CFR Part 91 without a flight plan.
Flight Sequence
The flight departed Felts Field (SFF), Spokane, Washington, around 1500, with the destination a private airstrip approximately 13 nautical miles northeast of SFF. The pilot reported his intention to make several slow, low passes over the airstrip. After departing, he climbed to 6,000 feet mean sea level and cycled the carburetor heat during descent. He made an initial low pass with full flaps and carburetor heat applied, followed by a go-around with carburetor heat off. During a second low pass in the same configuration, the pilot experienced engine roughness, a loss of power, engine backfiring, and a drop in engine rpm from 2,400 to 2,200. Carburetor heat was applied but did not increase rpm. Unable to maintain altitude, the pilot opted for a precautionary landing on the snow-covered airstrip. Upon touchdown, the airplane nosed over, resulting in substantial damage to both wing struts and the rudder.
Postaccident Examination
A postaccident examination overseen by a Federal Aviation Administration aviation safety inspector, including an engine run, revealed no preimpact malfunctions or failures that would have precluded normal operation. The carburetor heat/air box had full continuity, the butterfly valve reached full travel, and full control continuity from the cockpit throttle and mixture controls to the carburetor was confirmed.
Weather Conditions
At 1450, the weather reporting facility at Felts Field reported wind calm, visibility 10 miles, sky clear, temperature -7°C, dew point -9°C, and an altimeter setting of 30.52 inches of mercury.
Carburetor Icing Risk
The carburetor icing probability chart from FAA Special Airworthiness Information Bulletin (SAIB) CE-09-35, Carburetor Icing Prevention, indicated that the airplane was operating in an area associated with a serious risk of carburetor ice accumulation at descent power.