AD 97-19-14

This amendment supersedes an existing airworthiness directive (AD), applicable to Pratt & Whitney JT8D series turbofan engines, that currently requires inspections of low pressure turbine (LPT) blade sets for blade shroud crossnotch wear, and removal, if necessary. In addition, the current AD requires, as a terminating action to the inspections, installation of improved LPT containment hardware, and installation of an improved No. 6 bearing scavenge pump bracket bushing. This amendment keeps the compliance actions of the current AD intact but changes the compliance time for LPT containment hardware installation from the current calendar end-date to December 31, 1998, for engines that contain suspect 4th stage hubs identified by serial number. This amendment is prompted by a report of a fourth stage hub manufacturing defect that led to the failure of the hub and subsequent release of LPT blades. The actions specified by this AD are intended to prevent damage to the aircraftresulting from engine debris following an LPT blade, shaft, or hub failure.
The incorporation by reference of PW Alert Service Bulletin No. A6131, Revision 1, dated
May 16, 1995; PW Alert Service Bulletin No. A6131, Revision 2, dated July 28, 1997; PW Alert
Service Bulletin No. A6274, Original, dated November 7, 1996; and PW Alert Service Bulletin No.
A6274, Revision 1, dated December 9, 1996, is approved by the Director of the Federal Register as of October 24, 1997.
The incorporation by reference of all other publications listed in the regulations was
previously approved as of November 14, 1994 (59 FR 51842).

Final rule.

97-19-14 Pratt & Whitney: Amendment 39-10135. Docket 97-ANE-07. Supersedes AD 94-20-08, Amendment 39-9036.
Applicability: Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17, and -17R turbofan engines, installed on but not limited to Boeing 737 and 727 series aircraft, 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 (d) 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 damage to the aircraft resulting from engine debris following a low pressure turbine (LPT) blade, shaft, or hub failure, accomplish the following:
(a) For engines that do not contain 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 of PW ASB No. 6039, and either PW honeycomb third stage outer airseal Part Number (P/N) 801931, 802097, 797594, or 798279; or Pyromet Industries, Inc., honeycomb third stage outer airseal P/N PI9336; or McClain International, Inc., honeycomb third stage outer airseal P/N M2433; or a turbine case shield assembly installed in accordance with PW ASB No. 6039, Revision 3, dated October 15, 1993, or earlier revisions of PW ASB No. 6039; ora third stage blade set that has third stage turbine blades that were installed in accordance with PW SB No. 5331, dated October 27, 1982, 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 Part 1 of the Accomplishment Instructions of PW ASB No. A5913, Revision 6, dated October 15, 1993; or PW ASB No. A5913, Revision 5, dated August 10, 1992; or PW ASB No. A5913, Revision 4, dated February 20, 1992, as follows:
(i) Initially inspect the blade shroud crossnotches of the third stage LPT blade set when specified in paragraphs (a)(1)(i)(A) or (a)(1)(i)(B) of this AD, whichever occurs later. Engines that contain a third stage blade set that have third stage turbine blades that were installed per the requirements specified in PW Service Bulletin (SB) No. 5331, dated October 27, 1982, do not require the third stage blade set inspection.
(A) Inspect within 6,000 cycles or 6,000 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 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 1,000 cycles or 1,000 hours time in service since November 14, 1994, whichever occurs first.
(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. Engines that contain fan exhaust inner front duct segment assemblies that were installed per the requirements of PW ASB No. 6039, Revision 3, dated October 15, 1993, or earlier revisions of PW ASB No. 6039, do not require the fourth stage blade set inspection.
(A) Inspect within 6,000 cycles or 6,000 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 last blade shroud crossnotch repair that was accomplished per the requirements specified in Section 72-53-13 of PW JT8D Engine Manual P/N 481672; or
(B) Inspect within 1,000 cycles or 1,000 hours time in service since November 14, 1994, whichever occurs first.
(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, install the improved inner front fan exhaust duct and associated hardware in accordance with Part A of the Accomplishment Instructions of PW ASB A6110, Revision 1, dated October 15, 1993, as follows:
(i) For engines that have a 4th stage LPT hub installed with a serial number listedin PW ASB A6274, Table A, dated November 7, 1996, or Revision 1, dated December 9, 1996, install the improved inner front fan exhaust duct before December 31, 1998, or 8,000 hours time in service since November 14, 1994, or 7,000 cycles in service since November 14, 1994, whichever occurs first.
(ii) For engines that do not have a 4th stage LPT hub installed with a serial number listed in PW ASB A6274, Table A, dated November 7, 1996, or Revision 1, dated December 9, 1996, install the improved inner front fan exhaust duct before December 31, 1999, or 8,000 hours time in service since November 14, 1994, or 7,000 cycles in service since November 14, 1994, whichever occurs latest.
(3) At the next access to the third stage turbine air sealing ring, install the improved third stage turbine air sealing ring and associated hardware in accordance with Part B of the Accomplishment Instructions of PW ASB A6110, Revision 1, dated October 15, 1993. The installation of the improved thirdstage turbine air sealing ring must occur no later than December 31, 1999, or 8,000 hours time in service since November 14, 1994, or 7,000 cycles in service since November 14, 1994, whichever occurs latest.
Note 2: 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, 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, or Revision 1, dated May 16, 1995, or Revision 2, dated July 28, 1997. The installation of the improved No. 6 bearing scavenge pump bracket bushing must be accomplished no later than December 31, 1999, or 8,000 hours time in service since November 14, 1994, or 7,000 cycles since November 14, 1994, whichever occurs latest.
(5) Accomplishment of the installations required by paragraphs (a)(2), (a)(3), and (a)(4) of this AD constitutes terminating action to the repetitive inspections required by paragraph (a)(1) of this AD.
(b) For engines that do contain 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 of PW ASB No. 6039, and either PW honeycomb third stage outer airseal P/N 801931, 802097, 797594, or 798279; or Pyromet Industries, Inc., honeycomb third stage outer airseal P/N PI9336; or McClain International, Inc., honeycomb third stage outer airseal P/N M2433; or a turbine case shield assembly installed in accordance with PW ASB No. 6039, Revision 3, dated October 15, 1993, or earlier revisions of PW ASB No. 6039; or a third stage blade set that has third stage turbine blades that were installed in accordance with PW SB No. 5331, dated October 27, 1982, perform the installations required by paragraphs (a)(2), (a)(3), and (a)(4) 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 instructions 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. 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 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may beobtained 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 actions required by this AD shall be done in accordance with the following PW service documents:

Document No.
Pages
Revision
Date
ASB No. A5913
1-12
6
October 15, 1993
Total pages: 12.

ASB No. A6110
1-59
1
October 15, 1993
Total pages: 59.

ASB No. A6131
1-13
Original
August 24, 1993
Total pages: 13.

ASB No. A6131
1-14
1
May 16, 1995
Total pages: 14.

ASB No. A6131
1-21
2
July 28, 1997
Total pages: 21.

ASB No. A6274
1,2
1
December 9, 1996

3,4
Original
November 7, 1996

5
1
December 9, 1996

6-22
Original
November 7, 1996

23
1
December 9, 1996
Total pages: 23.

ASB No. A6274
1-23Original
November 7, 1996
Attachment NDIP-889
1-39
Original
November 1, 1996
Total pages: 62.

This incorporation by reference of PW ASB No. A5913, Revision 6, dated October 15, 1993; and PW ASB No. A6110, Revision 1, dated October 15, 1993; was previously approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 as of November 14, 1994 (59 FR 51842). 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 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 October 24, 1997.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 94-20-08, Amendment 39-9036 (59 FR 51842, October 15, 1994), applicable to Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17, and -17R series turbofan engines, was published in the Federal Register on April 1, 1997 (62 FR 15437). That action proposed to require inspections of low pressure turbine (LPT) blade sets for blade shroud crossnotch wear, and removal, if necessary. In addition, the current AD requires, as a terminating action to the inspections, installation of improved LPT containment hardware, and installation of an improved No. 6 bearing scavenge pump bracket bushing. The proposal would have reduced the compliance time for LPT containment hardware installation from the current calendar end-date to December 31, 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.
Eight commenters state that the more stringent compliance times should only be applicable to those engines that have a suspect 4th stage LPT hub installed. Otherwise, the proposed AD imposes an undue burden to operators, since the proposed AD does not specifically address the threat of the 4th stage hub suspect population. The commenters offer several alternatives, such as withdrawal of the NPRM, writing a stand alone AD, changing the compliance paragraph, and adding a paragraph to NPRM Docket No. 96-ANE-32. The FAA concurs with the comments and is changing the compliance paragraph accordingly. This final rule contains a new compliance schedule, which is intended to meet the threat of an blade release due to the failure of the 4th stage LPT hub. The threat of a 4th hub failure has been isolated to a suspect population of hubs listed in PW Alert Service Bulletin No. A6274, Revision 1, dated December 9, 1996.
Two commenters state that the third stage turbine air sealing ring should not have the more stringent compliance times, as the third stage turbine air sealing ring does not affect 4th stage LPT containment, which is why the compliance end-date is being moved up. The FAA concurs. The third stage turbine air sealing ring does not contribute to the containment of 4th stage LPT blades; therefore, the FAA has removed the more stringent compliance times for the third stage turbine air sealing ring in this final rule. The FAA has also relaxed the compliance time for the improved No. 6 bearing scavenge pump bracket bushing, as this part also does not contribute to the containment of 4th stage LPT blades released due to a 4th stage hub fracture.
One commenter states that the AD cannot be complied with on schedule as the replacement hardware is not available. The FAA does not concur. The manufacturer has advised the FAA that there are no current or foreseen shortages of hardware that will slow downoperators' ability to comply with the AD.
One commenter states that the proposed rule should be withdrawn, as the risk is within acceptable limits without any further action and the actions described in NPRM Docket No. 96-ANE- 32 are adequate to prevent future occurrences of uncontained failures from this cause. The FAA does not concur. While not yet published, the actions proposed in NPRM Docket No. 96-ANE-32 would, if adopted, minimize the threat of an uncontained blade release due to a hub fracture. The FAA has also evaluated the risk and crack growth analysis data and field experience for the 4th stage LPT hub and the data supports the conclusion that the failure mechanism is the loss of a 4th stage LPT blade and that the hub field management program must address non-containment of the LPT blade as well as the inspection of the LPT hub for cracks. The FAA feels the added measure of security offered by the improved containment is warranted in this case. However, the FAA agrees the more aggressive containment schedule should only apply to those hubs at highest risk of failing and releasing a blade as outlined in the compliance section described in previous responses to comments.
One commenter states that accomplishment of the actions described in PW ASB No. A6131, Revision 1, dated May 16, 1995, should be an acceptable alternative method of compliance to the AD's reference of the Original version of the ASB. The FAA concurs and has added reference to Revision 1 to the compliance section of this final rule.
One commenter states concern that the same containment hardware will be required for engines required to accomplish the actions described in AD 94-20-09 covering "A" model engines. The FAA does not concur. The suspect hubs are not approved for installation on "A" model engines; therefore, a similar condition does not exist for the "A" models.
Three commenters support the rule as proposed.
In addition, the FAA has reviewed and approved thetechnical contents of PW ASB No. A6274, Revision 1, dated December 9, 1996, and Original, dated November 7, 1996, that describe procedures for repetitive inspections of affected LPT hubs; and PW ASB No. A6131, Revision 2, dated July 28, 1997, that describes procedures for installation of the improved No. 6 bearing scavenge pump bracket bushing.
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 with the changes described previously.
The FAA has determined that the changes to the AD would neither increase the scope of the required actions over the current AD, nor increase the economic burden on operators over the costs of complying with the current AD. While the new AD alters the compliance times, operators should still be able to perform the required actions at scheduled maintenance. Therefore, the FAA has determined that this new AD will result in no additional economic impact.
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 itmay 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 removing amendment 39-9036 (59 FR 51842, October 15, 1994) and by adding a new airworthiness directive to read as follows: