What happened
While descending from 8,500 feet, the pilot of the aircraft experienced vibrations and a rough engine sound. During this time, the manifold pressure dropped slightly, and the fuel flow decreased from 21 to 10 gallons per hour (gph). In response, the pilot maintained a slow descent, activated the boost pump, and switched to an alternative fuel tank. This action caused the manifold pressure to increase and the fuel flow to rise to 15 gph.
As the aircraft descended through 2,500 feet, smoke entered the cockpit, and the pilot observed flames exiting the engine cowling vents. The pilot subsequently initiated a forced landing into a grass field. During the landing roll, the left wing of the aircraft struck a tree. The aircraft then proceeded through two fences and across a road before coming to rest in a plowed field. There were no injuries reported.
The investigation
An examination of the engine determined that the fuel injector line for the #2 cylinder had broken, which caused fuel to spray onto the turbocharger. Investigators found that the separation of the fuel injector line was caused by fatigue cracking that originated from a pre-existing damaged area on the line. Records indicated that Airworthiness Directive 93-02-05, which mandated inspections of these fuel injector lines, had been complied with 39 flight hours prior to the accident.