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94-20-09
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Turbine Blade Shaft Category - Engine Applicability: Pratt & Whitney (PW) Model JT8D-15A, -17A, and -17AR turbofan engines, installed on but not limited to Boeing 737 and 727 series aircraft, and McDonnell Douglas DC-9 series aircraft. Compliance: Required as indicated, unless accomplished previously. To prevent damage to the aircraft resulting from engine debris following a low pressure turbine (LPT) blade or shaft failure, accomplish the following: (a) For engines that do not contain PW honeycomb third stage outer airseal, Part Number (P/N) 801931, 802097, 797594, or 798279, or Parts Manufacturer Approval honeycomb third stage outer airseal P/N PI9336 or P/N M2433, and fan exhaust inner front duct segment assemblies that are installed in accordance with PW Alert Service Bulletin (ASB) No. 6039, Revision 3, dated October 15, 1993, or earlier revisions, accomplish the following: (1) Conduct initial and repetitive inspections on installed third and fourth stage LPT blade sets, and remove and replace with serviceable blade sets, as necessary, in accordance with the requirements of Part 2 of the Accomplishment Instructions of PW ASB No. A5913, Revision 6, dated October 15, 1993, as follows: (i) Initially inspect the blade shroud crossnotches of the third stage LPT blade set when specified in paragraph (a)(1)(i)(A) or (a)(1)(i)(B) of this AD, whichever occurs later, as follows: (A) Inspect within 3,000 cycles or 3,000 hours time in service, whichever occurs first, since new, since the last blade shroud crossnotch inspection specified in Section 72-53-12 of PW JT8D Engine Manual P/N 481672, or since the last blade shroud crossnotch repair that was accomplished per the requirements specified in Section 72-53-12 of PW JT8D Engine Manual P/N 481672; or (B) Inspect within 500 cycles or 500 hours time in service, whichever occurs first, after the effective date of this AD. (ii) Initially inspect the blade shroud crossnotches of the fourth stage LPT blade set when specified in paragraph (a)(1)(ii)(A) or (a)(1)(ii)(B) of this AD, whichever occurs later, as follows: (A) Inspect within 3,000 cycles or 3,000 hours time in service, whichever occurs first, since new, since the last blade shroud crossnotch inspection specified in Section 72-53-13 of PW JT8D Engine Manual P/N 481672, or since the last blade shroud crossnotch repair that was accomplished per the requirements specified in Section 72-53-13 of the PW JT8D Engine Manual P/N 481672; or (B) Inspect within 500 cycles or 500 hours time in service, whichever occurs first, after the effective date of this AD. (iii) Thereafter, inspect the third and fourth stage LPT blade sets in accordance with the procedures and intervals specified in PW ASB No. A5913, Revision 6, dated October 15, 1993. (2) At the next shop visit after the effective date of this AD; but not later than December 31, 1999, 8,000 hours time in service after the effective date of this AD, or 7,000 cycles after the effective date of this AD; whichever occurs latest, install the improved inner front fan exhaust duct and associated hardware in accordance with Part A of the Accomplishment Instructions of PW ASB No. A6110, Revision 1, dated October 15, 1993. (3) At the next access to the third stage turbine air sealing ring after the effective date of this AD, but not later than December 31, 1999, 8,000 hours time in service after the effective date of this AD or 7,000 cycles after the effective date of this AD, whichever occurs latest, install the improved third stage turbine air sealing ring and associated hardware in accordance with Part B of the Accomplishment Instructions of PW ASB No. A6110, Revision 1, dated October 15, 1993. NOTE: Third stage turbine outer air seal, P/N M2533, is an acceptable alternative to PW P/N 811962 for compliance with this paragraph. (4) At the next shop visit after the effective date of this AD, but not later than December 31, 1999, 8,000 hours time in service after the effective date of this AD or 7,000 cycles after the effective date of this AD, whichever occurs latest, install the improved No. 6 bearing scavenge pump bracket bushing in accordance with the Accomplishment Instructions of PW ASB No. A6131, dated August 24, 1993. (5) For engines that do not incorporate PW SB No. 5859, Revision 3, dated January 22, 1991, or earlier revisions, accomplish the following: at the next accessibility to the third and fourth stage LPT vane cluster assemblies after the effective date of this AD, but not later than December 31, 1999, 8,000 hours time in service after the effective date of this AD or 7,000 cycles after the effective date of this AD, whichever is latest, remove material from the inner platform leading edge on third and fourth stage LPT vane and vane cluster assemblies, and reidentify these modified vanes in accordance with the Accomplishment Instructions of PW SB No. 5748, Revision 5, dated August 3, 1993. (6) Accomplishment of the installations and modification required by paragraphs (a)(2), (a)(3), (a)(4), and (a)(5) of this AD constitutes terminating action to the inspections required by paragraph (a)(1) of this AD. (b) For engines that do contain PW honeycomb third stage outer airseal, P/N 801931, 802097, 797594, or 798279, or Parts Manufacturer Approval honeycomb third stage outer airseal P/N PI9336 or P/N M2433, and fan exhaust inner front duct segment assemblies that are installed in accordance with PW ASB No. 6039, Revision 3, dated October 15, 1993, or earlier revisions, perform the installations and modifications required by paragraphs (a)(2), (a)(3), (a)(4), and (a)(5) of this AD at the times specified in those respective paragraphs. (c) For the purpose of this AD, a shop visit is defined as an engine removal where engine maintenance entails separation of pairs of major mating engine flanges or the removal of a disk, hub, or spool at a maintenance facility that is capable of compliance with the requirements of this AD, regardless of other planned maintenance, except for field maintenance type activities performed at this maintenance facility in lieu of performing them on-wing or at another peripheral facility. (d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. NOTE: Information concerning the existence of approved alternative method of compliance with this AD, if any, may be obtained from the Engine Certification Office. (e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be accomplished. (f) The inspections and modification shall be done in accordance with the following service bulletins: Document No. Pages
Revision Date PW ASB No. A5913 1 PW ASB No. A6110
1 1 October 15, 1993 PW ASB No. A6131
1-13 Original August 24, 1993 PW SB No. 5748
1 5 August 3, 1993 This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pratt & Whitney, 400 Main Street, East Hartford, CT 06108. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (g) This amendment becomes effective on November 14, 1994. FOR FURTHER INFORMATION CONTACT: Mark A. Rumizen, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (617) 238-7137, fax (617) 238-7199.
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