88-24-05 PRATT & WHITNEY: Amendment 39-6018. Applies to Pratt & Whitney (PW) JT9D-3A, -7, -7A, - 7AH, -7H, -7F, -7J, and -20 turbofan engines.
Compliance is required as indicated, unless already accomplished.
To prevent sixth stage turbine inner airseal (IAS) rupture that can cause uncontained engine failure, accomplish the following:
(a) Modify sixth stage IAS Part Numbers (P/N) 751879, 660178, 661387, 667924, 677871, 704516, and 751881, in accordance with the Accomplishment Instructions contained in PW Service Bulletin 4835, Revision 5, dated September 27, 1983, as follows:
(1) Sixth stage IAS installed with either honeycomb or microfin type shrouds where engine build records indicate seal knife edge to shroud diametrical clearance less than 0.153 inches in either the front or the rear knife edge, within the next 500 cycles in service after the effective date of this AD.
(2) Sixth stage IAS installed with either honeycomb or microfin type shrouds whereengine build records indicate seal knife edge to shroud diametrical clearance equal to or more than 0.153 inches in both front and rear knife edges, at the next low pressure turbine (LPT) module shop visit after the effective date of this AD.
(b) Wet abrasive blast, visually inspect, and fluorescent penetrant inspect (FPI) at the next LPT module shop visit after the effective date of this AD, in accordance with the requirements of paragraph 4E, Inspection 01, Section 72-52-06, of the Engine Manual P/N 646028, Revision 74, sixth stage IAS assemblies P/N's 774836, 774827, 774829, 774825, 774831, 774834, and 774838, that have been modified in accordance with the requirements of PW SB 4835, Revision 3, dated June 12, 1978, or earlier revisions of the SB.
(c) Remove from service, prior to further flight, sixth stage IAS assemblies found cracked when accomplishing the requirements of paragraphs (a) or (b) above, and replace with serviceable parts.
NOTES: (1) Modification of sixth stage seals in accordance with the requirements of PW SB 4835, Revision 4, dated May 21, 1981, constitutes an equivalent means of compliance with this AD.
(2) For the purpose of this AD, an LPT module shop visit occurs when the LPT module rotor is removed from the case and vane assembly.
(d) Aircraft may be ferried in accordance with the provisions of FAR 21.197 and 21.199 to a base where the AD can be accomplished.
(e) Upon request, an equivalent means of compliance with the requirements of this AD may be approved by the Manager, Engine Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, Federal Aviation Administration, 12 New England Executive Park, Burlington, Massachusetts 01803.
(f) Upon submission of substantiating data by an owner or operator through an FAA Airworthiness Inspector, the Manager, Engine Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, may adjust the compliance times specified in this AD.
PW SB 4835, Revision 5, dated September 27, 1983, and the PW Engine Manual P/N 646028, Section 72- 52-06, Inspection 01, Paragraph 4E, Page 817, dated December 1, 1986, and Figure 810, Page 818, dated August 1, 1984, identified and described in this document, are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to Pratt & Whitney, Publication Department, P.O. Box 611, Middletown, Connecticut 06457.
These documents also may be examined at the Office of the Assistant Chief Counsel, Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, Massachusetts 01803, Room 311, Rules Docket Number 86-ANE-38, between the hours of 8:00 a.m. and 4:30 p.m., Monday through Friday, except federal holidays.
This amendment, 39-6018, becomes effective on December 15,1988.