93-18-08 PRATT & WHITNEY CANADA: Amendment 39-8693. Docket 91-ANE-42. Supersedes AD 91- 06-01, Amendment 39-6911 which superseded AD 88-22-03, Amendment 39-6274.
Applicability: Pratt & Whitney Canada (PWC) Model JT15D-1, -1A, -1B, -4, -4B, -4C, and -4D series turbofan engines installed on but not limited to Cessna Citation I, Citation II/SII and Citation 500, Aerospatiale Corvette, Mitsubishi Diamond 1/1A and Agusta S211 aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent a high pressure turbine (HPT) assembly failure, and an inflight engine shutdown or loss of engine power, accomplish the following:
(a) For PWC JT15D-4B, -4C, and -4D series engines for which the requirements of PWC Service Bulletin (SB) JT15D 72-7297, Revision 1, dated May 25, 1991, and either PWC SB JT15D 72-7296, Revision 3, dated October 18, 1991, or PWC SB JT15D 72-7307, Revision 2, dated December 19, 1991, have not been accomplished as of the effective date of this AD, accomplish the following:
(1) Borescope inspect the HPT assembly for HPT blade shift in accordance with the inspection requirements outlined in Appendix 1 of this AD, as follows:
Appendix 1
1. Inspect high pressure turbine (HPT) blades for evidence of blade shift using a 3 or 4 mm flexible borescope. Blade forward movement in excess of 0.020 inch is reason for removal of the HPT for repair.
2. Inspection with a 5 or 6 mm borescope has proven to be extremely difficult and is not recommended.
3. Borescope access is achieved by passing the borescope probe between the blades of the low pressure turbine (LPT) assembly. With the borescope in position, rotation of the high pressure rotor via the accessory gearbox starter-generator driveshaft allows all HPT blades to be inspected. The extent of blade shift may be assessed by comparing with the HPT blade serration to serration pitch, which is 0.090 inch.
(i) Within 25 hours time in service (TIS) or 30 days after the effective date of this AD, whichever occurs first, for those engines which have accumulated on the effective date of this AD, greater than 275 hours TIS since the last inspection performed in accordance with AD 91-06-01, or since the last hot section inspection (HSI), or since new, if not previously inspected.
(ii) Prior to accumulating 300 hours TIS since the last inspection performed in accordance with AD 91-06-01, or since the last HSI, or since new if not previously inspected, for those engines which have accumulated on the effective date of this AD 275 hours or less TIS since the last inspection performed in accordance with AD 91-06-01 or since the last HSI, or since new, if not previously inspected.
(iii) Thereafter, reinspect the HPT assembly for HPT blade shift in accordance with Appendix 1 of this AD at intervals not to exceed 300 hours TIS since the last inspection.
(iv) Remove from service prior to further flight, and replace with a serviceable assemblythose HPT assemblies with evidence of forward blade movement in excess of the 0.020 inch limit as provided in Appendix 1 of this AD. Serviceable assemblies include HPT assemblies removed from engines which have completed an HSI, or that portion of the HSI requiring deblading and re-riveting the turbine assembly in accordance with the applicable JT15D Maintenance Manuals.
(2) Incorporate high turbine (HT) blade retaining rivets in accordance with PWC SB JT15D 72- 7297, Revision 1, dated May 25, 1991, at the next shop visit when the engine is disassembled sufficiently to afford access to the HPT assembly.
(3) Incorporate the new or reworked HT stator assembly in accordance with applicable PWC SB JT15D 72-7307, Revision 2, dated December 19, 1991, or PWC SB JT15D 72-7296, Revision 3, dated October 18, 1991, at the next shop visit when the engine is disassembled sufficiently to afford access to the HPT assembly.
(4) Initial and repetitive borescope inspections performed inaccordance with paragraph (a)(1) of this AD are not required once the new HPT blade retention rivets and the new or reworked HT stator assembly are incorporated in accordance with paragraph (a)(2) and (a)(3) of this AD.
(b) For PWC JT15D-1, -1A, -1B, and -4 series engines for which the requirements of PWC SB JT15D 72-7297, Revision 1, dated May 25, 1991, have not been accomplished as of the effective date of this AD, accomplish the following:
(1) Borescope inspect the HPT assembly within 300 hours TIS after the effective date of this AD for HPT blade shift in accordance with the inspection requirements outlined in Appendix 1 of this AD.
(i) Thereafter, reinspect at intervals not to exceed 300 hours TIS since last inspection.
(ii) Remove from service prior to further flight HPT assemblies that exhibit forward blade movement in accordance with paragraph (a)(1)(iv) of this AD.
(2) Incorporate HT blade retaining rivets in accordance with PWC SB JT15D 72-7297, Revision 1, dated May 25, 1991, at the next shop visit when the engine is disassembled sufficiently to afford access to the HPT assembly.
(3) Initial and repetitive borescope inspections in accordance with paragraph (b)(1) of this AD are no longer required once the new HPT blade retention rivets are incorporated in accordance with paragraph (b)(2) of this AD.
(c) For the purpose of this AD, accomplishment of the actions described in the following earlier revisions of these SB's constitutes accomplishment of actions described in the current revisions of these SB's referenced in this final rule:
(1) PWC SB JT15D 72-7297, Original, dated December 18, 1990;
(2) PWC SB JT15D 72-7296, Revision 2, dated September 5, 1991; Revision 1, dated May 15, 1991; and Original, dated February 8, 1991;
(3) PWC SB JT15D 72-7307, Revision 1, dated October 18, 1991; and Original, dated May 15, 1991.
(d) An alternative method of compliance or adjustment of the compliance time that provides anacceptable 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 methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(e) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.
(f) The inspections, replacement, and modification shall be done in accordance with the following service documents:
Document No.
Pages
Issue
Date
PWC SB JT15D 72-7297R1
1-8
Rev. 1
May 25, 1991
Total pages: 8
PWC SB JT15D 72-7307R2
1-9
Rev. 2
December 19, 1991
Total pages: 9
PWC SB JT15D 72-7296R3
1-8
Rev. 3
October 18, 1991
Total pages: 8
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 Canada, Box 10, Longueuil, Quebec, Canada J4K 4X9. 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 24, 1993.