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Proposed Rule

Airworthiness Directives; Pratt & Whitney PW4164, PW4168, and PW4168A Series Turbofan Engines

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Pratt & Whitney PW4164, PW4168, and PW4168A series turbofan engines. AD 98-04-14 currently requires initial and repetitive torque checks for loose or broken front pylon mount bolts, replacement, if necessary, with new bolts, and establishment of a new cyclic life limit. This action would add initial and repetitive torque checks of new material MP159 front pylon mount bolts. In addition, this action would add initial and repetitive visual inspections of the primary mount thrust load path. This proposal is prompted by the introduction into service of the new MP159 front pylon mount bolts and the determination through fatigue testing that the forward engine mount bearing housings have insufficient fatigue life expectancy. The actions specified by the proposed AD are intended to prevent front pylon mount bolt and primary mount thrust load path failure, which could result in engine separation from the aircraft.

DATES:

Comments must be received by April 24, 2000.

ADDRESSES:

Submit comments to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 97-ANE-44, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: “9-ane-adcomment@faa.gov”. Comments sent via the Internet must contain the docket number in the subject line. Comments may be inspected at this location between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays.

The service information referenced in the proposed rule may be obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-8860, fax (860) 565-4503. This information may be examined at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

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FOR FURTHER INFORMATION CONTACT:

Tara Goodman, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7130, fax (781) 238-7199.

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SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 97-ANE-44.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 97-ANE-44, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

On February 6, 1998, the Federal Aviation Administration (FAA) issued airworthiness directive AD 98-04-14, Amendment 39-10326 (63 FR 9730, February 26, 1998), applicable to Pratt & Whitney (PW) PW4164, PW4168, and PW4168A series turbofan engines. That AD requires initial and repetitive inspections for loose or broken front pylon mount bolts, replacement, if necessary, with new bolts, and establishment of a new cyclic life limit of 11,000 cycles in service (CIS) for INCO 718 material bolts. That action was prompted by flight testing that revealed higher than predicted loads for front pylon mount bolts, resulting in decreased service life. That condition, if not corrected, could result in front pylon mount bolt failure, which could result in engine separation from the aircraft.

Events Since the Issuance of the AD

Since the issuance of that AD, PW introduced a new material bolt to address the fatigue life shortfall of the original INCO 718 material bolts, part number (P/N) 54T670. MP159 material bolts, P/N 51U615, do not require a life limit. However, in a bolt-out configuration, fatigue testing indicated that there was insufficient margin to meet the 8,000 cycles-in-service (CIS) Start Printed Page 15879minimum inspection requirement for the aircraft. Therefore, the FAA determined a repetitive torque check interval of 1,000 CIS, plus or minus 250 CIS, to be consistent with the torque check interval required for the INCO 718 material bolts, P/N 54T670.

In addition, fatigue testing of the secondary thrust load path using the measured flight loads demonstrated that with a primary thrust load path failure, there is insufficient fatigue life expectancy of the forward engine mount bearing housing. Therefore, a repetitive visual inspection of the primary mount thrust load path at a 1,000 CIS, plus or minus 250 CIS, interval is required

Service Information

The FAA has reviewed and approved the technical contents of the following PW Service Bulletins (SBs):

  • No. PW4G-100-A71-20, dated December 9, 1999, that describes procedures for torque checking MP159 material bolts, P/N 51U615.
  • No. PW4G-100-A71-18, dated September 15, 1999, that describes procedures for visually inspecting the primary mount thrust load path.

Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would supersede AD 98-04-14 to maintain the inspections of the INCO 718 material bolts, P/N 54T670, and replacement, if necessary, with serviceable parts. This superseding AD would also maintain the life limit of 11,000 CSN for the INCO 718 material bolts, P/N 54T670. However, based on a comment received to AD 98-04-14, the initial torque check would now be required for bolts with 1,000 or fewer CSN before accumulating 1,250 CSN, or 250 CIS after the effective date of this AD, whichever occurs first.

New Actions

This AD would also require initial and repetitive torque checks of MP159 material bolts, P/N 51U615, and the primary mount thrust load path. If any of the bolts are found loose or broken, all four bolts must be replaced with serviceable bolts.

Also, this AD would require initial and repetitive visual inspections of the primary mount thrust load path. If any components of the primary mount thrust load path are found cracked, then this AD would require replacement with serviceable parts.

Economic Analysis

There are approximately 75 engines of the affected design in the worldwide fleet. The FAA estimates that 10 engines installed on aircraft of US registry would be affected by this proposed AD, that it would take approximately 3 work hours per engine to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Required parts would cost approximately $18,832 per engine. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $190,120.

Agency Findings

This proposal does not have federalism implications, as defined in Executive Order 13132, because it would not have a substantial direct effect 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this proposal.

For the reasons discussed above, I certify that this proposed regulation (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

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List of Subjects in 14 CFR Part 39

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The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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[Amended]

2. Section 39.13 is amended by removing Amendment 39-10326, (63 FR 9730, February 26, 1998), and by adding a new airworthiness directive to read as follows:

Pratt & Whitney: Docket No. 97-ANE-44. Supersedes AD 98-04-14, Amendment 39-10326.

Applicability: Pratt & Whitney (PW) PW4164, PW4168, and PW4168A series turbofan engines, with front pylon mount bolts, part numbers (P/Ns) 54T670 or 51U615, installed. These engines are installed on but not limited to Airbus Industrie A330 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 (e) 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 front pylon mount bolt and primary mount thrust load path failure, which could result in engine separation from the aircraft, accomplish the following:

INCO 718 Material Bolts Torque Checks

(a) Perform initial and repetitive torque checks of INCO 718 material front pylon mount bolts, P/N 54T670, and replace, if necessary, with new bolts, in accordance with the Accomplishment Instructions of Pratt & Whitney Service Bulletin (SB) No. PW4G-100-A71-9, Revision 1, dated November 24, 1997, as follows:

(1) For front pylon mount bolts, P/N 54T670, with 1,000 or fewer cycles-since-new (CSN) on the effective date of this AD, perform torque checks in accordance with Part (A) of the Accomplishment Instructions of the SB at the earliest of:

(i) Before accumulating 1,250 CSN, or

(ii) Within 250 cycles-in-service (CIS) after the effective date of this AD, or

(iii) The next engine removal for any cause.

(2) Thereafter, perform torque checks at intervals not less than 750 or greater than 1,250 CIS since last torque check, not to exceed 11,000 CSN, in accordance with Part (A) of the Accomplishment Instructions of the SB.

(3) For front pylon mount bolts, P/N 54T670, with more than 1,000 CSN but less than 5,750 CSN on the effective date of this AD, accomplish the following:

(i) Perform an initial torque check within 250 CIS after the effective date of this AD, or at the next engine removal for any cause, whichever occurs first, in accordance with Part (A) of the Accomplishment Instructions of the SB.

(ii) Thereafter, perform torque checks at intervals not less than 750 or greater than 1,250 CIS since last torque check, not to exceed 11,000 CSN.

(4) For front pylon mount bolts, P/N 54T670, with 5,750 or more CSN but less Start Printed Page 15880than 8,000 CSN on the effective date of this AD, accomplish the following in accordance with Part (B) of the Accomplishment Instructions of the SB:

(i) Perform an initial torque check within 250 CIS after the effective date of this AD, or prior to the next engine removal for any cause, whichever occurs first.

(ii) Thereafter, perform torque checks at intervals not less than 750 or greater than 1,250 CIS since last torque check, not to exceed 11,000 CSN.

(5) For front pylon mount bolts, P/N 54T670, with 8,000 or more CSN but less than 11,000 CSN on the effective date of this AD, perform an inspection in accordance with the schedule and procedures of the Appendix to the SB.

(6) Prior to further flight, replace all four bolts in accordance with Part (A), Paragraph 1(D) of the Accomplishment Instructions of the SB, if any are found loose or broken.

INCO 718 Material Bolts Life Limit

(b) This AD establishes a new life limit of 11,000 CSN for front pylon mount bolts, P/N 54T670. Except as provided in paragraph (e) of this AD, no front pylon mount bolts, P/N 54T670, may exceed this new life limit after the effective date of this AD.

MP159 Material Bolts Inspections

(c) Perform initial and repetitive torque checks of front pylon mount bolts, P/N 51U615, in accordance with the Accomplishment Instructions of PW SB PW4G-100-A71-20, dated December 9, 1999, as follows:

(1) Perform the initial torque check at the earliest of the following:

(i) Before accumulating 1,250 CSN, or

(ii) Within 250 CIS after the effective date of this AD, or

(iii) The next engine removal for any cause.

(2) Thereafter, perform torque inspections at intervals not less than 750 or greater than 1,250 CIS since last torque inspection.

(3) Prior to further flight, replace all four bolts, if any are found loose or broken.

Primary Mount Thrust Load Path Inspections

(d) Perform initial and repetitive visual inspections of the primary mount thrust load path, in accordance with the Accomplishment Instructions of PW4G-100-A71-18, dated September 15, 1999, as follows:

(1) Perform the initial visual inspection at the earliest of the following:

(i) Before accumulating 1,250 CSN, or

(ii) Within 250 CIS after the effective date of this AD, or

(iii) The next engine removal for any cause.

(2) Thereafter, perform visual inspections at intervals not less than 750 or greater than 1,250 CIS since last visual inspection.

(3) Prior to further flight, replace all cracked parts with serviceable parts.

Alternative Methods of Compliance

(e) 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 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.

Ferry Flights

(f) 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 inspection requirements of this AD can be accomplished.

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Issued in Burlington, Massachusetts, on March 17, 2000.

Mark C. Fulmer,

Assistant Manager, Engine and Propeller Directorate, Aircraft Certification Service.

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[FR Doc. 00-7225 Filed 3-23-00; 8:45 am]

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