AD 98-23-08

This amendment adopts a new airworthiness directive (AD), applicable to certain Pratt & Whitney (PW) PW4000 series turbofan engines not incorporating modifications described in certain PW service bulletins listed in the applicability section, that requires high pressure compressor (HPC) blade tip grinding of the rotor assembly, installation of aluminum oxide coated HPC blade tips in stages 9 through 12, modification of HPC 8th through 14th stage stators, incorporation of 1st stage high pressure turbine (HPT) vanes with increased airflow area which also requires additional HPT hardware modifications, and incorporation of HPC 13th-15th stage zirconium oxide blade tips. This amendment is prompted by reports of HPC surge caused by excessive HPC rear stage rotor-to-case clearance. The actions specified by this AD are intended to prevent HPC surge, which can result in engine power loss at a critical phase of flight such as takeoff or climb.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of January 12, 1999.

Final rule.

98-23-08 Pratt & Whitney: Amendment 39-10873. Docket 97-ANE-53-AD.
Applicability: Pratt & Whitney (PW) Model PW4152, PW4056, PW4156, PW4256, PW4052, PW4158, PW4060, PW4160, PW4460, PW4050, PW4060A, PW4156A, PW4062, PW4462, PW4060C, and PW4650 turbofan engines, not incorporating at least one of the modifications described in the PW service bulletins (SBs) and listed in items (1) through (6), excluding those engines having a (-3) identifier next to the engine model number on the engine data plate. These engines are installed on but not limited to Boeing 767 and 747 series aircraft, McDonnell Douglas MD-11 series aircraft, and Airbus A310 and A300-600 series aircraft.
(1) PW4ENG 72-484, Revision 3, dated July 1, 1997, or earlier revisions, PW4ENG 72-486, Revision 1, dated November 23, 1994, or original issue.
(2) PW4ENG 72-484, Revision 3, dated July 1, 1997, or earlier revisions, PW4ENG 72-575, Revision 1, dated June 30, 1997, or original issue, PW4ENG 72-486, Revision 1,dated November 23, 1994, or original issue.
(3) PW4ENG 72-514, Revision 1, dated August 2, 1996, or original issue.
(4) PW4ENG 72-490, Revision 1, dated August 2, 1994, or original issue.
(5) PW4ENG 72-504, Revision 1, dated May 9, 1995, or original issue.
(6) PW4ENG 72-572, dated June 16, 1995.
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 high pressure compressor (HPC) surge, which can result in engine power loss at a critical phase of flight such as takeoff, accomplish the following:
(a) Within 1,400 cycles in service (CIS) after the effective date of this AD, or prior to June 30, 1999, whichever occurs first, perform the following modifications:
(1) Incorporate stage 9 through 12 aluminum oxide blade tips and grind HPC blade tips at the rotor assembly in accordance with the Accomplishment Instructions of PW SB No. PW4ENG-72-484, Revision 3, dated July 1, 1997, concurrently with the requirements of paragraph (a)(4) of this AD.
(2) Modify HPC 8th-14th stage stators in accordance with the Accomplishment Instructions of PW SB No. PW4ENG-72-486, Revision 1, dated November 23, 1994.
(3) Modify the 1st stage high pressure turbine (HPT) cooling duct (TOBIDuct), install a metering plug in the Number 2 bearing thrust balance vent tube, and incorporate 1st stage HPT vanes with increased airflow area in accordance with the Accomplishment Instructions of PW SB No. PW4ENG-72-514, Revision 1, dated August 2, 1996.
(4) Incorporate HPC 13th-15th stage zirconium oxide blade tips in accordance with the Accomplishment Instructions of PW SB No. PW4ENG-72-575, Revision 1, dated June 30, 1997.
(5) If at any time prior to the compliance time of this AD incorporation of the requirements of any one of the SBs, identified in items (4), (5), and (6) in the applicability section of this AD is accomplished on any engine, then such an engine will not be subject to the requirements of this AD and no further action is required.
(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 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.
(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 SBs:

Document No
Pages
Revision
Date
PW4ENG-72-484
1-16
3
July 1, 1997

17-78
1
November 8, 1994

79
2
March 10, 1995

80,81
3
July 1, 1997
Total Pages: 81.

PW4ENG-72-486
1-31
1
November 23, 1994
Total Pages: 31.

PW4ENG-72-514
1-6
1
August 2, 1996

7Original
June 23, 1994

8-35
1
August 2, 1996
Total Pages: 35.

PW4ENG-72-575
1-43
1
June 30, 1997
Total Pages: 43.

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.
(e) This amendment becomes effective on January 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) PW4000 series turbofan engines not incorporating modifications described in certain PW service bulletins listed in the applicability section was published in the Federal Register on June 18, 1998 (63 FR 33295). That action proposed to require high pressure compressor (HPC) blade tip grinding of the rotor assembly, installation of aluminum oxide coated HPC blade tips in stages 9 through 12, modification of HPC 8th through 14th stage stators, incorporation of 1st stage high pressure turbine (HPT) vanes with increased airflow area which also requires additional HPT hardware modifications, and incorporation of HPC 13th-15th stage zirconium oxide blade tips.
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 requests a change to the Compliance Section to allow the accomplishment of either PW Service Bulletins (SBs) No. PW4ENG-72-514, or the appropriate nozzle guide vane and TOBI duct section of SB PW4ENG-72-504. The commenter wants to have a choice to incorporate the pertinent sections of SB PW4ENG-72-504 after the effective date of this AD and still comply with the AD. The FAA concurs, provided that all of the requirements of that SB are incorporated, since incorporation of only the pertinent sections will not produce a certified engine configuration. Engines that have incorporated the modifications in SB PW4ENG-72-504 already are exempted from the AD based upon the applicability. If an operator wants to exercise this choice after the effective date of this AD, instead of incorporating the modifications in SB PW4ENG-72-514, that choice will produce an airworthy engine to an equivalent level of the modifications in SB PW4ENG-72-514. Thereare two other SBs listed in the applicability section: SB PW4ENG-72-490 and PW4ENG-72-572 that accomplish equivalent actions to SB PW4ENG-72-504. Therefore, a paragraph has been added to the compliance section clarifying that if the modifications contained in certain SBs listed in the applicability paragraph are incorporated after the effective date of this AD, no further action is required.
One commenter states that it has already complied with the requirements of this AD and that those requirements are effective in preventing surges from occurring in service.
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 these changes will neither increase the economic burden on any operator nor increase the scope of the AD.
There are approximately 187 engines of the affected design in the worldwide fleet. The FAA estimates that there are currently 61 engines installed on aircraft of U.S. registry that would be affected by this AD. Required parts would cost approximately $20,000 per engine. Based on these figures, the total cost impact of the AD, including labor costs, is estimated to be $1,220,000.
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: