Uncontained Fan Blade Separation in No. 2 Engine During Climb (N133JC)

Incident Overview During a climb through 38,000 feet, the aircraft experienced an uncontained fan blade separation in the No. 2 engine. The event resulted in significant structural damage to the airframe, with fragments exiting the engine nacelle and penetrating the vertical stabilizer. ## Investigation Findings The investigation determined that one of the first-stage compressor fan blades, identified by serial number EB2506, had separated approximately 8 inches above the blade platform. Fragments from blade number 8 exited through the left fan cowl in three distinct locations and penetrated the vertical stabilizer. ## Root Cause Analysis The blade separation was traced to a 0.34-inch long fatigue crack that began in a weld adjacent to a patch. The fan blade had previously undergone a patch repair and was subjected to four non-destructive tests, including X-ray, fluorescent penetrant, ultrasonic, and eddy current inspections.