Cessna 170B N4380B accident near Big Lake, Alaska

Probable cause

The pilot’s failure to utilize carburetor heat while flying in conditions conducive to carburetor icing, which resulted in a total loss of engine power.

NTSB analysis

During a landing to a remote off-airport gravel bar located along a river, while at about 20 ft above ground level, the airplane’s engine lost power. The engine then surged briefly before a total loss of engine power occurred. Subsequently, the airplane landed short of the gravel bar in the river and the airplane nosed over. The airplane sustained substantial damage to the left wing and empennage.

A postaccident examination revealed no mechanical failures or malfunctions. A postaccident engine run was successfully performed. A non-aviation fuel tank was installed on the top of the fuselage to provide a fuel source. Air was applied to the fuel lines to provide pressure to ensure proper fuel flow, no contaminates were noted in the fuel lines.

The temperature and dew point were entered into a carburetor icing probability chart, which coincided with the “serious icing in glide power” category.

Text from the NTSB. Open the NTSB docket for ANC20LA099 for the full record.