AD 99-04-05

This amendment adopts a new airworthiness directive (AD), applicable to certain Pratt & Whitney (PW) JT9D series turbofan engines, that requires a fluorescent penetrant inspection (FPI) of the rear skirt of the diffuser case for cracks, and, if necessary, blending down to minimum wall thickness to remove cracks and subsequent FPI to determine if cracks have been removed, polishing, and shotpeening. If the cracks are shown by subsequent FPI not to have been removed, this AD requires removing the diffuser case from service and replace with a serviceable part. This amendment is prompted by a report of a diffuser case rupture during takeoff roll that resulted in damage to the aircraft. The actions specified by this AD are intended to prevent diffuser case rupture due to cracks, which can result in an uncontained engine failure and damage to the aircraft.
The incorporation by reference of certain publications listed in the regulations is approved by the Director of the FederalRegister as of April 12, 1999.

Final rule.

99-04-05 Pratt & Whitney: Amendment 39-11029 Docket 98-ANE-28-AD.
Applicability: Pratt & Whitney (PW) Model JT9D-7Q, -7Q3, -59A, and -70A turbofan engines, with diffuser cases, part numbers (P/Ns) 772173, 772173-001, 772173-002, 782222, 782222-001, and 782222-002, installed. These engines are installed on but not limited to Boeing 747 series, McDonnell Douglas DC-10 series, and Airbus A300 series aircraft.
Note 1: This airworthiness directive (AD) applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
Compliance: Required as indicated, unless accomplished previously.
To prevent diffuser case rupture due to cracks, which can result in an uncontained engine failure and damage to the aircraft, accomplish the following:
(a) At the next piece-part exposure of the diffuser case after the effective date of this AD, accomplish the following in accordance with PW Service Bulletin (SB) No. JT9D-6329, dated May 20, 1998:
(1) Perform a fluorescent penetrant inspection (FPI) for cracks in accordance with the procedures and criteria stated in the SB of the diffuser case rear skirt paying particular attention to areas around the dog bone-shaped bosses identified in the SB.
(2) If no indications of cracks are found in accordance with the procedures and criteria stated in the SB, no further action is required.
(3) If indications of cracks are found in accordance with the procedures and criteria stated in the SB, remove the diffuser case from service, replace with a serviceable part, or blend the cracks as needed down to the minimum wall thickness to remove cracks in accordance with the procedures and criteria stated in the SB.
(4) After blending down in accordance with the procedures and criteria stated in the SB, perform a subsequent etch and FPI for cracks, as follows:
(i) If no indications of cracks are found in accordance with the procedures and criteria stated in the SB, polish and shot-peen the area around each dog bone boss in accordance with the procedures and criteria stated in the SB.
(ii) If indications of cracks are found in accordance with the procedures and criteria stated in the SB, remove the diffuser case from service and replace with a serviceable part.
(b) For the purpose of this AD, piece-part exposure is defined as when the part is considered completely disassembled when done in accordance with the disassembly instructions in the engine manufacturer's manual, to give access to the dog bone-shaped bosses in the diffuser case rear skirt.
(c) 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. Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office.
Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(d) 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.
(e) The actions required by this AD shall be done in accordance with the following PW SB:

Document No
Pages
Date
JT9D 6329
1-42
May 20, 1998
Total Pages: 42.

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 St., East Hartford, CT 06108; telephone (860) 565-6600, fax (860) 565-4503. Copies may be inspected at the FAA, New England Region, Office of the Regional 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.
(f) This amendment becomes effective on April 12, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Pratt & Whitney (PW) JT9D series turbofan engines was published in the Federal Register on August 31, 1998 (63 FR 46200). That action proposed to require fluorescent penetrant inspection (FPI) of the rear skirt of the diffuser case for cracks, and, if necessary, blending down to minimum wall thickness, to remove cracks, subsequent FPI to determine if cracks have been removed, and polishing and shotpeening. If the cracks are shown by subsequent FPI not to have been removed, the proposed AD would require removing the diffuser case from service for possible weld repair or replacement with serviceable parts. The actions would be required to be accomplished in accordance with PW Service Bulletin (SB) No. JT9D-6329, dated May 20, 1998.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
One commenter states that the proposed AD only requires blending out if an indication of a crack is found. The AD should be amended to require blending out of all tooling and other surface marks at piece-part exposure, whether or not cracks are found, in order to remove the danger of them becoming crack initiation sites at a future date. The FAA does not concur. The referenced SB explains that scratches and toolmarks can lead to cracking. The criteria in the SB also state any questionable indications be marked as a crack. Although surface tooling mark conditions may exist in other locations on the diffuser case, there has been no field experience to indicate that an unsafe condition exists in other locations.
The same commenter states the proposed AD concentrates solely on the area around the dog bone bosses. With a highly stressed part such as a diffuser casing, attention should be paidto the whole component and the AD should be amended to reflect this. The FAA concurs in part. Paragraph (a) of the AD has been changed to reflect the intent of the SB to perform an FPI of the rear skirt of the diffuser case with particular attention to the area around the dogbone location because it is a high stress area. At this time, however, the FAA has determined that it is not necessary to require an FPI of the entire diffuser case. The JT9D Engine Manual (Part Number (P/N) 777210) Inspection -01 Task 72-41-03-22-000 contains a full diffuser case FPI as a prerequisite procedure for visual and dimensional inspection per SPOP 82. That inspection procedure also contains cautionary note to pay particular attention to the rear rail.
Two commenters have no objection to the proposed AD.
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.There are approximately 566 engines of the affected design in the worldwide fleet. The FAA estimates that 157 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 68 work hours per engine to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $640,560.
The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" underExecutive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air Transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: