Accident Overview
On August 25, 2012, at approximately 1100 mountain daylight time, a Cessna 140, registration N140XX, sustained substantial damage during a forced landing following a partial loss of engine power. The accident occurred in the vicinity of the Black Hills Airport - Clyde Ice Field (SPF), Spearfish, South Dakota. The student pilot, who was conducting a solo cross-country flight, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was conducted under 14 Code of Federal Regulations Part 91.
Flight History
The cross-country flight originated at 1000 from the Philip Airport (PHP), Philip, South Dakota, and was the final leg of a multi-airport flight. The pilot reported that the flight was uneventful until nearing SPF. While setting up for a downwind leg, the pilot applied carburetor heat, after which the engine RPM dropped below 1000. Unable to continue to the planned runway, the pilot elected to land in an adjacent field.
Forced Landing and Damage
During the landing roll, the airplane struck a barbed wire fence and nosed over, coming to rest inverted. The accident resulted in substantial damage to the vertical stabilizer and rudder. The pilot exited the airplane uninjured.
Post-Accident Examination
A post-accident examination of the engine revealed foreign object debris (FOD) lodged in the throttle body beneath the carburetor venturi. The debris appeared to be remnants of aluminum tape or foil. Additionally, 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. It is unknown how long the FOD had been present below the carburetor venturi. The airplane and engine had operated normally for about three flight hours after its last annual inspection on May 3, 2012. The tachometer time at the time of the annual inspection was 1,473 hours, and at the time of the accident was 1,476 hours.