What happened
After receiving clearance to land, the pilot notified air traffic control that the aircraft was in trouble and descending. Witnesses observed the airplane flying at a low altitude and heard the engine sputter before it stopped running entirely. During the descent, the left wing struck a tree, leading to an impact with the ground. The aircraft was completely destroyed by a fire that ignited following the crash.
The investigation
An examination of the engine revealed that the fuel injector line for cylinder #1 had failed at the outer diameter (OD) surface. This failure occurred at the manifold end near the B-nut fitting. A metallurgical analysis determined that the separation was caused by fatigue cracking which originated at the OD surface of the tube, specifically at the edge containing the brazed filler metal.
Findings
Investigators identified intergranular corrosion at the origin of the fracture. This corrosion occurred during the manufacturing process when the line became sensitized near the brazing joint. Additionally, there was no evidence that the tube had been clamped at its midpoint as required by the engineering drawing.