What happened
While climbing through 38,000 feet, the aircraft experienced an uncontained fan blade separation within the No. 2 engine. The event resulted in fragments from the blade exiting the left fan cowl in three separate locations and penetrating the vertical stabilizer.
The investigation
Investigators determined that one of the first-stage compressor fan blades (S/N EB2506) had separated approximately 8 inches above the blade platform. The investigation focused on the failure of blade #8, which was found to have a 0.34-inch long fatigue crack. This crack originated in a weld located adjacent to a patch. Records indicated that the fan blade had undergone a previous patch repair and had been subjected to four different types of non-destructive testing, including X-ray, fluorescent penetrant, ultrasonic, and eddy current inspections.