Cessna 172E N3647S accident near Gettysburg, Pennsylvania

Probable cause

The total loss of engine power due to carburetor icing. Contributing to the accident was the pilot's failure to maintain a proper approach speed during the forced landing, which resulted in impact with trees.

NTSB analysis

The private pilot, who was also the airplane owner, was conducting a local personal flight. About 30 minutes after takeoff, during a descent from 3,000 to 1,500 ft mean sea level, the airplane experienced a total loss of engine power; the pilot then attempted a forced landing to a grass field. The airplane's approach speed was too fast for landing and the airplane overflew the selected field, eventually impacting trees at the edge of an adjacent field.

Subsequent examination of the airframe and engine revealed no evidence of any preimpact mechanical anomalies that would have precluded normal operation. Before the accident flight, the airplane had been stored for an extended period with automotive fuel in the tanks. Although long-term storage with automotive fuel can lead to varnish or gum deposits that may block or restrict fuel flow, the newly-replaced carburetor was found full of fuel with no foreign material or deposits present, and fuel was observed to flow freely from the fuel tanks to the carburetor during postaccident testing. The weather conditions at the time of the accident were conducive to the formation of serious carburetor icing at glide engine power settings when using aviation-grade gasoline. Given that the use of automotive gasoline is known to result in the formation of carburetor icing at higher ambient temperature and lower humidity conditions than aviation gasoline, it is likely that the loss of engine power was the result of carburetor icing.

Text from the NTSB. Open the NTSB docket for ERA15LA363 for the full record.