COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES General Electric Turbine Engines - CF6 Series AD/CF6/17 Stage 1 Fan Rotor Disc 3/91 Applicability: CF6 - 6, -45, -50, -80A. Requirement: Inspect the stage 1 fan disc dovetail post for cracks in accordance with the technical requirements of the FAA AD 91-01-04 Amdt 39-6847. Note: The GE SB 72-999, 965 and 575 covering the -50/-45, -6 and -80A series respectively refer. Compliance: As specified in the Requirement Document. Background: Five stage 1 fan discs have been discovered with cracks in the dovetail post area. The defect has the potential for multiple blade release, engine power loss and uncontained engine failure.