COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES General Electric Turbine Engines - CT7 Series AD/CT7/7 Amdt 1 Stage 1 and Stage 2 Gas Generator Turbine Disks 7/98 Applicability: General Electric CT7-5, -7, and -9 series engines incorporating Gas Generator Turbine (GGT) disks, P/No. 6064T06P01(Stage 1) or 6064T12P01(Stage 2). Requirement: Perform a one time eddy current inspection of affected GGT disks in accordance with General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 dated 13 February 1997. Note 1: Disks inspected per the original issue of this Directive satisfy the intent of this amendment to the Directive. Note 2: FAA AD 97-25-07 also refers. Note 3: FAA AD 97-25-07 supersedes FAA AD 97-05-12. Compliance: Unless previously accomplished: (a) For Stage 1 GGT disks identified in Table 1 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated 8,500 or more Cycles Since New (CSN) on the effective date of this Directive, inspect at the next GGT module removal or within 3 months of the effective date of this Directive whichever occurs first. (b) For Stage 1 GGT disks identified in Table 1 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated less than 8,500 CSN, inspect at the next GGT module removal but not to exceed 9,000 CSN. (c) For Stage 1 GGT disks identified in Table 2 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated 11,500 or more CSN on the effective date of this Directive, inspect at the next GGT module removal or within 3 months of the effective date of this Directive whichever occurs first. (d) For Stage 1 GGT disks identified in Table 2 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated less than 11,500 CSN, inspect at the next GGT module removal but not to exceed 12,000 CSN. (e) For Stage 2 GGT disks identified in Table 3 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated 8,500 or more (CSN) on the effective date of this Directive, inspect at the next GGT module removal or within 3 months of the effective date of this Directive whichever occurs first. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES (f) For Stage 2 GGT disks identified in Table 3 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated less than 8,500 CSN, inspect at the next GGT module removal but not to exceed 9,000 CSN. (g) For Stage 2 GGT disks identified in Table 4 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated 11,500 or more (CSN) on the effective date of this Directive, inspect at the next GGT module removal or within 3 months of the effective date of this Directive whichever occurs first. (h) For Stage 2 GGT disks identified in Table 4 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated less than 11,500 CSN, inspect at the next GGT module removal but not to exceed 12,000 CSN. (i) For Stage 1 and Stage 2 GGT disks not identified in Tables 1 through 4 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated 8,500 CSN or more on the effective date of this Directive, inspect at the next GGT module removal or within 3 months of the effective date of this Directive whichever occurs first. (j) For Stage 1 and Stage 2 GGT disks not identified in Tables 1 through 4 of General Electric Service Bulletin (CT7-TP series) A72-393 Revision 1 that have accumulated less than 8,500 CSN, inspect at the next GGT module removal but not to exceed 9,000 CSN. This amendment becomes effective on 18 June 1998. Background: This Directive is prompted by a report of an uncontained Stage 2 GGT disk failure on take-off. The most likely cause of the failure of the disk was machining damage to a cooling hole during manufacture. GGT disk rupture can result in an uncontained failure that could cause damage to the aircraft. This amendment reflects a revision to the General Electric SB that corrects the respective disk serial numbers in the various tables to avoid confusion where the same serial number appears in more than one table. In addition, the inspection thresholds have been increased and the calendar time intervals decreased to comply with GE's risk analysis model. The original issue of this Directive became effective on 17 July 1997.