AD 99-15-01

This amendment adopts a new airworthiness directive (AD), applicable to certain Pratt & Whitney PW4000 series turbofan engines, that reduces life limits of certain 4th stage low pressure turbine (LPT) disks. It also allows the original life limits of the disks to be restored if reoperation is performed to incorporate the original slotted cooling hole configuration. This amendment is prompted by reports that a change of a cooling hole geometry, which was introduced in the design of certain 4th stage LPT disks, inadvertently caused a reduction on the cooling air flow to the disk and an increased level of stress. The actions specified by this AD are intended to prevent an uncontained disk failure and damage to the aircraft.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of September 14, 1999.

Final rule.

99-15-01 PRATT & WHITNEY: Amendment 39-11220. Docket 97-ANE-55-AD.
Applicability: Pratt & Whitney Model PW4056, PW4152, PW4156A, PW4164, PW4168, and PW4460 turbofan engines, with 4th stage low pressure turbine (LPT) disks, part number (P/N) 50N924, serial numbers (S/Ns) CLDL BX2061, CLDL BX6620, CLDL BX2054, CLDL BX2055, CLDL BX6596, CLDL BX2059, CLDL BX2060, CLDL BX6600, CLDL BX6597, CLDL BX6599, CLDL BX6601, CLDL BX6598, CLDL BX6604, CLDL BX6605, CLDL BX6602, CLDL BX6609, CLDL BX6607, CLDL BX6612, CLDL BX6611, CLDL BX6610, CLDL BX6608, CLDL BX6606, CLDL BX6615, CLDL BX6616, CLDL BX6619, CLDL BX2058, and CLDL BX6603 installed. These engines are installed on but not limited to Airbus Industrie A330, Boeing 747, and McDonnell Douglas MD-11 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 requirementsof 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 an uncontained disk failure and damage to the aircraft, accomplish the following:
(a) Except as provided in paragraph (b) of this AD, prior to accumulating 7,500 cycles in service (CIS), remove the affected 4th stage LPT disks and replace them with new or serviceable parts.
Note 2: A list of the affected 4th stage LPT disks, identified by P/N and S/N, appears in the "Applicability" paragraph for this AD.
(b) Restoration of the original life limits on the affected disks may be accomplished as follows:
(1) Reoperation performed on the LPT disks installed in PW4164 and PW4168 model engines, in accordance with Pratt & Whitney (PW) Service Bulletin (SB) No. PW4G 100-72-105, dated November 12, 1997, prior to 7,000 CIS to incorporate the slotted cooling air configuration may restore the life limit to 15,000 CIS.
(2) Reoperation performed on the LPT disks installed in PW4156A and PW4460 model engines in accordance with PW SB No. PW4ENG 72-657, dated November 25, 1997, prior to 5,500 CIS to incorporate the slotted cooling air configuration may restore the life limit to 15,000 CIS.
(3) Reoperation performed on the LPT disks installed in PW4056 and PW4152 model engines in accordance with PW SB No. PW4ENG 72-657, dated November 25, 1997, prior to 4,500 CIS to incorporate the slotted cooling air configuration may restore the life limit to 20,000 CIS.(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 3: 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 airplane 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's:

Document No
Pages
Date
PW4G 100-72-105
1-19
November 12, 1997
Total Pages:19

PW4ENG 72-657
1-22
November 25, 1997
Total Pages: 22

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, Publications Department, Supervisor Technical Publications Distribution, M/S 132-30, 400 Main St., East Hartford, CT 06108; telephone (860) 565-8770. 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 September 14, 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 Pratt & Whitney Model PW4056, PW4152, PW4156A, PW4164, PW4168, and PW4460 turbofan engines was published in the Federal Register on March 9, 1998 (63 FR 11381). That action proposed to reduce life limits of affected 4th stage low pressure turbine (LPT) disks, identified by serial number (S/N). It would also allow the original life limits to be restored, if reoperation is performed to incorporate the slotted cooling air configuration.
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 it does not own any of the disks affected by this AD, and will therefore not be affected by it. The commenter, however, states that the 4th stage LPT disk was subjected to a design change butretained the same part number. The commenter states that for tracking purposes it is desirable to change the part number. The FAA agrees with the concept; however, this issue addresses practices at the manufacturer and not this action, since both part number and serial numbers are identified for tracking purposes. The FAA will communicate this request to the manufacturer for future considerations.
One commenter states that the economic analysis should be revised to note that the labor cost is accurate when the engine is torn down to obtain access to the LPT. The FAA concurs and has added this language to the economic analysis of this final rule.
Two commenters state that they do not own any of the affected disks and that therefore would not be affected by the proposed rule.
One commenter supports the rule as proposed.
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require theadoption of the rule as proposed. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.
There are approximately 27 engines of the affected design in the worldwide fleet. The FAA estimates that there are currently no engines installed on aircraft of U.S. registry that will be affected by this AD, but if one were installed, it would take approximately 4 work hours per engine to accomplish the required actions when the engine is torn down to obtain access to the LPT, and that the average labor rate is $60 per work hour. Required parts will cost approximately $240 per engine. Based on these figures, the total cost impact per engine is estimated to be $480.
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: