NTSB Issues Urgent Recommendations for GE CF6-45/50 Turbofans
The NTSB issued two urgent safety recommendations to the FAA that pertain to the General Electric GE CF6-45/50 series turbofan engine, which is found on the Airbus A300B, DC-10-15/-30, Boeing 747-200 and -300 and KC-10. The first recommendation asks that the FAA require operators of aircraft equipped with this engine to immediately perform blade borescope inspections (BSI) of the high-pressure turbine rotor every 15 flight cycles until the current turbine disk can be redesigned and replaced with one that can withstand the unbalance vibration forces from the high-pressure rotor. Second, the Safety Board wants the FAA to require GE to immediately redesign the disk.
The NTSB issued an additional recommendation for a requirement that operators perform fluorescent penetrant inspections of CF6-45/50 low-pressure turbine (LPT) stage-three disks at every engine shop visit and another recommendation to require installation of the replacement disk once it is available.
All four recommendations apply to the LPT stage -three rotor disk in the GE CF6-45/50 series engines that can fail unexpectedly when excited by high-pressure rotor unbalance. This could then lead to an uncontained engine event. In fact, the NTSB is aware of four uncontained engine failures due to this problem.