Incident Summary
Shortly after takeoff, the pilot reported that he had "a problem" and needed to return immediately. Witnesses observed dark black smoke coming from both engines. The airplane subsequently collided with a tree located 1/2 mile northeast of the runway threshold.
Investigation Findings
Analysis of fuel samples revealed the presence of approximately 50% jet fuel. The right propeller was found feathered. Disassembly of the right engine showed a hole burned in the number 5 piston. Disassembly of the left engine revealed piston edges eroded down to the first compression ring. Fuel filler restrictors had been installed in the airplane's fuel tanks, but the fuel truck did not have the restrictive mating nozzle. The fuel truck was owned by the fuel vendor and leased to the fixed-base operator (FBO).
Probable Cause
The official probable cause was improper servicing of the airplane with jet fuel, which resulted in preignition and/or detonation and subsequent failure of pistons in both engines. A factor related to the accident was the lack of a restrictive mating nozzle on the refueling truck.