CHI08CA280 · Cessna 150G

The pilot reported that as she approached the destination airport after a 1-hour cross-country flight, she reduced engine power to approximately 2,300 rpm in order to descend to traffic pattern altitude. During the downwind leg, she further reduced engine power to 2,000 rpm to slow the airplane to for the approach. As she initiated a turn to base leg, she made a final reduction of engine power and activated the carburetor heat. During the turn to base leg, the engine began to lose power. The loss of engine power was reported to be gradual, not instantaneous, occurring over a period of approximately 5 seconds. The engine did not respond to throttle and mixture control movements. The pilot stated that the loss of engine power occurred 700-800 feet above ground level while on base leg. She said that she was worried about stalling the airplane and established a descent to remain above stall speed. The airplane landed in a grassy area about 50 feet short of the runway. Shortly after touchdown the nose gear collapsed and the airplane came to an abrupt stop. The temperature and dew point in the vicinity of the accident site were 17 degrees and 12 degrees Celsius, respectively. Calculations using a carburator icing chart indicate the possibility of moderate carburetor icing at cruise power and serious icing at descent power under the indicated conditions.

Verbatim NTSB analysis and probable cause from the NTSB dataset