Cessna 140 N140XX accident near Spearfish, South Dakota

Probable cause

The partial loss of engine power due to debris lodged beneath the throttle body of the carburetor venturi.

NTSB analysis

After an uneventful cross-country flight, the solo student pilot was setting up to enter the downwind leg of the traffic pattern at his destination airport. When he applied carburetor heat, the engine rpm dropped below 1000. Unable to continue to the planned runway, the student pilot elected to land the airplane in an adjacent field. During the landing roll, the airplane struck a barbed wire fence and nosed over, coming to rest inverted. Postaccident examination of the engine revealed debris lodged in the throttle body beneath the carburetor venturi. The debris appeared to be remnants of aluminum tape or foil. Additionally, what appeared to be a small piece of exhaust insulation or asbestos wrap was found within the carburetor heat box. No other anomalies with the engine or airframe were discovered that could have contributed to the partial loss of engine power. It is unknown how long the foreign object debris was present below the carburetor venturi; however, the airplane had operated for about 3 flight hours since its most recent annual inspection, which was conducted 3 months before the accident flight. The presence of debris lodged beneath the carburetor venturi is consistent with the student pilot's statement that he experienced a loss of power and engine rpm when carburetor heat was applied.

Text from the NTSB. Open the NTSB docket for CEN12LA580 for the full record.