AD 97-19-12

This amendment adopts a new airworthiness directive (AD), applicable to Pratt & Whitney JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A,-11, -15, -17, and -17R series turbofan engines, that requires initial and repetitive fluorescent penetrant and eddy current inspections of 4th stage low pressure turbine (LPT) hubs for cracks, and, if necessary, replacement with serviceable parts. This amendment is prompted by a report of an uncontained 4th stage LPT blade release. The actions specified by this AD are intended to prevent a 4th stage LPT blade release due to hub cracking, which can result in an uncontained engine failure and damage to the aircraft.

Final rule.

97-19-12 Pratt & Whitney: Amendment 39-10133. Docket 96-ANE-32.
Applicability: Pratt & Whitney (PW) Models JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17, and -17R turbofan engines, with 4th stage low pressure turbine (LPT) hubs identified by serial number (S/N) in Table A of PW Alert Service Bulletin (ASB) No. A6274, Revision 1, dated December 9, 1996. These engines are installed on but not limited to Boeing 727 and 737 series, and McDonnell Douglas DC-9 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 (b) 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 4th stage LPT blade failure due to hub cracking, which can result in an uncontained engine failure and damage to the aircraft, accomplish the following:
(a) Perform fluorescent penetrant inspection (FPI) and eddy current inspection (ECI) of affected 4th stage LPT hubs for cracks, in accordance with Paragraph 2A of PW ASB No. A6274, Revision 1, dated December 9, 1996, as follows:
(1) Inspect at the next time after the effective date of this AD that the hub is removed from the module and has been debladed.
(2) Thereafter, inspect each time the hub is removed from the module and has been debladed.
(3) Remove from service any cracked 4th stageLPT hub and replace with a serviceable part.
(b) 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 forward their requests 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.
(c) 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.
(d) The actions required by this AD shall be done in accordance with the following PW ASB:

Document No
Pages
Revision
Date
A62741-23
1
December 9, 1996
Total Pages: 23.

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, Publication Department, Supervisor Technical Publications Distribution, M/S 132-30, 400 Main St., East Hartford, CT 06108; telephone (860) 565-7700, fax (860) 565-4503. 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.
(e) This amendment becomes effective on November 18, 1997.

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 Pratt & Whitney JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17, and -17R series turbofan engines was published in the Federal Register on January 9, 1997 (62 FR 1299). That action proposed to require initial and repetitive fluorescent penetrant inspections (FPI) and eddy current inspections (ECI) of affected 4th stage low pressure turbine (LPT) hubs for cracks, and, if necessary, replacement with serviceable parts.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
Four commenters support the rule as proposed.
One commenter states that the inspection should be performed in less than 5,900 cycles in service (CIS), as that was the number of CIS between the last FPI and the uncontained eventthat prompted this AD. The FAA does not concur. The FAA has evaluated the data and risk management plan supplied by PW that includes risk analysis, crack growth analysis, and field experience for the 4th stage LPT hubs. That data supports the FAA conclusion that the unsafe condition is an uncontained release of an LPT blade. The FAA concludes the loads introduced by the cracking of the 4th stage hub are not sufficient to result in an uncontained release of the entire 4th stage hub. Further, the analyses support the risk management plan, which includes a focused, ultra high sensitivity FPI and ECI at the next piece part exposure. The FAA has also concluded that the unsafe condition resulting from an uncontained blade failure can be mitigated by a reduced compliance time for installing LPT containment hardware on engines in which certain 4th stage LPT hubs are installed. The revised compliance requirement is described in AD 97-19-14.
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.
The FAA estimates that 381 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 6 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 $137,160.
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" under Executive 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: