Accident Details
On September 22, 2020, at about 1900 Alaska daylight time, a Cessna 170B (N4380B) was substantially damaged in an accident near Big Lake, Alaska. The pilot, who was the sole occupant, was not injured. The flight was conducted under 14 Code of Federal Regulations Part 91.
The pilot reported that he was landing on a remote off-airport gravel bar along a river. During short final, at approximately 20 ft above ground level, the engine began to sputter, followed by a partial loss of power. The engine then surged briefly before experiencing a total loss of power, with the propeller windmilling. The airplane touched down in the river short of the intended landing area and nosed over, coming to rest inverted in the water. Substantial damage occurred to the left wing and empennage.
Prior to the accident, the pilot had flown for about 1.5 hours and estimated that about 1.7 hours of fuel remained in the tanks. He stated that he had been using carburetor heat during previous landings on the same gravel bar and that the fuel selector was set to BOTH during the approach.
Postaccident Examination
A Federal Aviation Administration (FAA) aviation safety inspector examined the recovered airplane and did not observe any abnormalities. Fuel drained from the gascolator appeared normal, with no signs of contamination. A postaccident engine run was successfully performed using a non-aviation fuel tank mounted on top of the fuselage. Compressed air was applied to the fuel lines to ensure proper flow, and no contaminants were detected.
Weather
The nearest weather observation station, located about 25 nautical miles from the accident site, reported at the time of the accident a temperature of 55.4°F and a dew point of 37.4°F. According to the carburetor icing probability chart in FAA Special Airworthiness Information Bulletin CE-09-35, these conditions correspond to "serious icing in glide power."