Incident Summary
After takeoff, at about 1,000 ft above ground level, the crew of a Boeing 747-240 heard a 'thudding noise.' This was followed by a loss of power in the number two engine. The crew completed an engine shut down and made an uneventful landing at the departure airport.
Aircraft and Engine Details
The airplane was equipped with General Electric CF6-50E2 engines. Examination revealed that the low pressure turbine module, which included a portion of the fan mid shaft (FMS) and turbine rear frame, was missing. The airplane sustained damage to the left wing leading and trailing edge flaps, the left main wing landing gear doors, and the number one engine.
Fan Mid Shaft Examination
Examination of the number two engine revealed a fracture face on the forward end of the fan mid shaft. The fracture showed multiple fatigue origins and circumferential cracks. There were also areas on the FMS that were heat affected. The FMS had previously been installed in a CF6-50 engine that had sustained a failure of the number 3 bearing inner race. The engine had been inspected by company personnel, and records did not reflect that they inspected the FMS for heat affected material. Fatigue cracks located in the heat-affected areas were found to have Sermetel paint and debris in the cracks.
Conclusion
The investigation documented the mechanical findings but did not assign a probable cause.