Incident Overview
During the takeoff roll, the No. 4 engine experienced an uncontained failure. The flight crew rejected the takeoff, and the aircraft came to a stop on the remaining runway. Airport emergency personnel responded and extinguished a fire that broke out in the engine following the failure.
Aircraft Damage
Post-incident examination of the aircraft revealed damage to the engine, pylon, right wing, flaps, aileron, right horizontal stabilizer, and fuselage. This damage was caused by debris released during the uncontained engine failure.
Engine Examination
Detailed inspection of the failed engine showed that the low pressure turbine fifth stage hub had ruptured. Approximately 180 degrees of the hub rim had separated, along with the associated blade attachment slots and blades. The rupture originated from an area of well-oxidized, intergranular fracture that began at a tierod hole. No apparent defect was observed along the edge of the tierod hole that would account for crack initiation and propagation to critical length.
Conclusion
The investigation did not explicitly identify a probable cause for the engine failure. The findings noted the presence of an oxidized intergranular fracture originating at a tierod hole, but no manufacturing or material defect was detected in that area.