What happened
During the initial climb following takeoff, the number 2 engine of the aircraft caught fire. In response to the fire, the flight crew executed an emergency landing. Following the landing, an evacuation was initiated for all 369 passengers and 17 crewmembers. During the process, the slide/rafts at doors 4R and 5R failed to operate as intended. As a result, all occupants evacuated the aircraft through doors 1R, 2R, and 3R.
The investigation
Mechanical examinations focused on both the evacuation equipment and the engine failure. Investigators found that the 4R slide/raft had a fractured inflation hose near the regulator end swivel wire groove. No abnormalities were discovered during the examination of the 5R slide/raft that would have prevented normal operation.
Regarding the engine, an under cowl fire was identified in the area of the accessory gearbox. A teardown of the engine revealed that the High-Pressure Compressor (HPC) forward air seal stack had disengaged from the hub. Additionally, the key washer and retaining nut were found to be disengaged from the threads on the HPC rear shaft. Evidence of light, grooved scoring was present on the HPC shaft where the retaining nut had become loose. While dimensional measurements of the HPC rear hub were within specification, the HPC hub snap diameter for the front air seal was found to be worn out-of-limits.