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Proposed Rule

Airworthiness Directives; Pratt & Whitney JT9D-7R4 Series Turbofan Engines

Document Details

Information about this document as published in the Federal Register.

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Start Preamble

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines. This proposal would require initial and repetitive fluorescent penetrant inspection (FPI) of the high pressure turbine (HPT) 1st stage disk aft lugs, and if the aft lug(s) are cracked, replacement of the HPT 1st stage disk and HPT 1st stage airseals. Also, for certain configuration HPT disk assemblies, this proposal would require replacement of the HPT 1st stage airseals with newly designed airseals at the next accessibility. This proposal is prompted by reports of cracks in HPT 1st stage disk firtrees and failure of firtree lugs. The actions specified by the proposed AD are intended to prevent 1st stage HPT disk firtree fracture, which could result in an uncontained engine failure, and damage to the airplane.

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DATES:

Comments must be received by April 30, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-NE-35-AD, 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 8:00 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) 565-6600, 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:

Peter White, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7128, 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 in triplicate 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 action 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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NE-35-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRM's

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. 2000-NE-35-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

The FAA is aware of nine occurrences of HPT 1st stage disk firtree cracking, and one in-service event involving the failure of two adjacent firtree lugs installed on Pratt & Whitney JT9D-7R4 series turbofan engines, which resulted in the liberation of three HPT blades. Investigation and analysis have traced the cause of this disk lug cracking to the pre-bowing of the HPT aft 1st stage airseals. The pre-bow can place excessive stresses on the HPT 1st stage disk lugs that retain the airseals, and result in fatigue cracking of the lugs. The manufacturer has redesigned these HPT 1st stage airseals with revised pre-bow and reduced weight, to lower the stresses on the HPT 1st stage disk lugs. Onset of this fatigue cracking is dependent upon the HPT disk material; powder disks (P/N 787521) experience cracking much sooner than Waspalloy disks (P/N 797621). Therefore, the FAA has determined that the HPT 1st stage airseals on disk assemblies with powder disks (P/N 787521) must be replaced at the next hot section shop visit. PW and the FAA have developed a fleet management plan requiring initial and repetitive fluorescent penetrant inspection of the HPT 1st stage disk aft lug fillet radius for cracking, and replacement of the HPT 1st stage airseals at next HPT shop visit for engines configured with powder HPT 1st stage disk assembly (P/N 787521). The actions specified by the proposed AD are intended to prevent 1st stage HPT disk firtree fracture, which could result in an uncontained engine failure, and damage to the airplane.

Service Information

The FAA has reviewed the technical contents of Pratt & Whitney Service Bulletin (SB's): JT9D-7R4-72-566, dated May 26, 2000; JT9D-7R4-72-567, dated May 26, 2000 and JT9D-7R4-72-568, dated May 26, 2000, that describe procedures for incorporation of new HPT 1st stage airseals, fluorescent penetrant inspection (FPI) of HPT disk rear lugs, and incorporation of new HPT disks and redesigned HPT 1st stage airseals. These documents were developed by PW and are generally consistent with the fleet management plan defined in this AD, and can be utilized for reference.

Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, this proposed AD would prevent HPT 1st stage disk firtree fracture by requiring initial and repetitive FPI of the 1st stage disk aft lug, and if cracked, replacement of the HPT 1st stage disk and HPT 1st stage airseals. In addition, the proposed AD would require replacement of HPT 1st stage airseals with redesigned HPT 1st stage airseals for certain HPT disk configurations.

Cost Analysis

There are approximately 324 engines of the affected design in the worldwide fleet. The FAA estimates that 47 engines installed on aircraft of U.S. registry would be affected by this proposed AD. Although forced engine removals are not anticipated the first year as a result of this proposed action, a maximum of two removals will be assumed. It would take approximately 86 work hours per engine to accomplish the proposed actions, and the average labor rate is $60 per work hour. Based on these figures, the total labor cost impact of the proposed AD on U.S. operators the first year is estimated to be $24,520. Hardware costs the first year for HPT 1st stage airseals replaced by SB JT9D-7R4-72-566 are estimated to be $128,000, based on replacement costs of $147,110 per disk and $45,143 for sideplates, discounted for average 1/3 life lost at removal. Total combined labor and hardware costs for the first year are therefore estimated to be $140,000

The following year, it is estimated that inspections will result in a maximum of three engines requiring forced replacement of the HPT 1st stage disk and HPT 1st stage airseals due to cracking. Due to these forced removals, approximately 1/3 of the disk life will be lost. The total combined hardware and labor cost is estimated to be approximately $210,000. The total cost impact of this proposal on U.S. operators in the first two years is expected to be approximately $350,000.

Regulatory Impact

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 Start Printed Page 12442between 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 adding the following new airworthiness directive:

Pratt & Whitney: Docket No. 2000-NE-35-AD.

Applicability: This airworthiness directive (AD) is applicable to Pratt & Whitney (PW) JT9D-7R4E1, JT9D-7R4E4, JT9D-7R4G2, JT9D-7R4H1 series turbofan engines which incorporate HPT 1st stage disk assembly P/N 787521 or HPT 1st stage disk assembly P/N 797621. These engines are installed on but not limited to Boeing 747 and 767 series and Airbus A300 and A310 series airplanes.

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: Compliance with this AD is required as indicated, unless accomplished previously.

To prevent HPT disk firtree fracture, which could result in an uncontained engine failure, and damage to the airplane, accomplish the following:

HPT 1st Stage Airseal Replacement

(a) For engines that incorporate HPT 1st stage disk assembly P/N 787521, replace HPT 1st stage airseals with P/N 820121 at the next hot section shop visit. Information on replacement of the HPT 1st stage airseal is contained in PW service bulletin (SB) JT9D-7R4-72-566, dated May 26, 2000.

Fluorescent Penetrant Inspection (FPI)

(b) Inspect the HPT 1st stage disk aft lug fillet radius for cracks in accordance with Paragraph 4 of the Accomplishment Instructions of PW SB JT9D-7R4-72-567, dated May 26, 2000, and Table 1 of this AD as follows:

Table 1

HPT 1st stage disk assemblyHPT 1st stage diskInitial inspectionRepetitive inspection interval
(1) P/N 787521P/N 825701 or P/N 827201Before the latest of 4,000 CSN or 4,000 cycles since last HPT disk lug fluorescent penetrant inspection (CSLI), or 500 CIS after the effective date of this ADWithin 4,000 CSLI.
(2) P/N 797621(i) P/N 829401 with air seals P/N's 797355, 796760, 803979, 797355-001 installedBefore the latest of 5,000 CSN or CSLI, or 500 CIS after the effective date of this ADWithin 4,000 CSLI.
(ii) 829401 with air seals P/N 820121 installedBefore the latest of 5,000 CSN or 5,000 CSLI, or 500 CIS after the effective date of this ADWithin 6,000 CSLI.

(c) Replace any disks that have crack indications. Information on replacement of the disk is contained in PW SB JT9D-7R4-72-568, dated May 26, 2000.

Terminating Action

(d) Installation of HPT disk P/N 820321 with redesigned HPT 1st stage airseal P/N 820121 is considered terminating action to the initial and repetitive inspection requirements of paragraph (b) this AD. Information on installation of the HPT disk is contained in PW SB JT9D-7R4-72-568, dated May 26, 2000.

Definition

(e) For the purpose of this AD, a hot section shop visit is defined as any time the HPT rotor is disassembled.

Alternative Methods of Compliance

(f) 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 (ECO). Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the ECO.

Special Flight Permits

(g) 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.

Start Signature

Issued in Burlington, Massachusetts, on February 19, 2001.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification Service.

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[FR Doc. 01-4764 Filed 2-26-01; 8:45 am]

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