Primary finding
Probable cause
The pilot’s improper management of the fuel mixture, which resulted in an over-rich fuel mixture condition and a subsequent partial loss of engine power.
Investigator assessment
Analysis narrative
The pilot stated that, during taxi and takeoff, he set the engine fuel mixture control to the full-rich position. While in the crosswind turn, the engine lost partial power, and the pilot made a forced landing in a forested area. Examination of the engine revealed that the No. 1 cylinder's spark plugs were completely carbon-fouled and that the Nos. 2 through 4 cylinders' spark plugs were badly sooted. It is likely that the pilot did not properly manage the engine mixture, which led to an over-rich fuel mixture condition during the takeoff and resulted in a partial loss of engine power.
Source record
Factual narrative
On August 10, 2013, about 0927 central daylight time, a Brian Douglas BA-100 airplane, N27BD, was substantially damaged during a forced landing near Killeen, Texas. The pilot, who was the sole occupant, was not injured. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which departed without a flight plan. The local flight originated from Skylark Field Airport (KILE), near Killeen, Texas, about 0925. According to the pilot's statement, the airplane departed Runway 01 at KILE and the engine lost partial power while in the crosswind turn. The pilot considered turning back toward the runway, but elected not to because he was concerned that the airplane might enter into a spin. The pilot maneuvered the airplane and made a forced landing, during which both wings were structurally damaged during impact with trees. Following the accident, the engine and fuel system were examined by an airframe and powerplant mechanic. Both fuel tanks were about ¾ full, with no evidence of fuel contamination. The magnetos and ignition leads were operable. Both spark plugs for the #1 cylinder were completely carbon fouled and the spark plugs for #2-#4 cylinders were significantly sooted. The pilot stated that he had set the engine mixture control to the full rich position during taxi and takeoff for the accident flight.