What happened
Following an uneventful preflight inspection and engine run-up, the pilot began the takeoff sequence. As the aircraft climbed through 1,000 feet, the pilot observed a puff of white smoke. The pilot elected to return to the airport to land; however, as the aircraft approached the airfield, a fire erupted. This forced the pilot to perform an emergency landing in a nearby field.
The investigation
Investigators examined the engine and found that the fuel injection line for the number 5 cylinder had become disconnected from the manifold assembly fitting. This fitting was located below the number 3 cylinder assembly. The b-nut was found off the threads of the fitting, floating along the steel fuel line. While the fuel line and b-nut showed no visual damage, and the b-nut could be reassembled and tightened to the manifold without binding, the disconnection had allowed for the fire. Records indicated that the number 5 cylinder had been replaced 5.4 hours prior to the accident. A representative from the engine manufacturer noted that there are no published torque values provided by the manufacturer for this specific b-nut.