Incident Sequence
The pilot had received clearance to land when they called out that they were in trouble and going down. Witnesses observed the aircraft at low altitude and heard the engine sputtering before it stopped. The left wing then struck a tree, causing the airplane to impact the ground. The subsequent post-crash fire completely destroyed the aircraft.
Engine Examination
During teardown of the engine, investigators found that the cylinder #1 fuel injector line had failed at the outer diameter (OD) surface at the manifold end near the B-nut fitting. Metallurgical examination showed that the separation resulted from fatigue cracking, which originated at the OD surface of the tube at the edge of the brazed filler metal.
Manufacturing Defect
The cracking was traced to intergranular corrosion present at the fracture origin. This corrosion occurred during manufacture, when the line was sensitized near the brazing joint. Additionally, there was no evidence of clamping of the tube at its midpoint, as required by the engineering drawing.
Conclusions
The failure of the fuel injector line led to a loss of engine power, resulting in the aircraft's descent and collision with terrain. The investigation identified two contributing factors: fatigue cracking caused by intergranular corrosion from the manufacturing process, and the absence of a required midpoint clamp on the fuel line.