01-21895. Airworthiness Directives; Pratt & Whitney JT9D-7R4 Series Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines. This proposal would require a one-time inspection of low pressure turbine (LPT) 5th stage disks for evidence of blend repairs and mechanical damage, and replacement based on the extent of those repairs and damage. This proposal is prompted by a report of a PW JT9D-7R4G2 turbofan engine that experienced an uncontained failure of the LPT 5th stage disk. The actions specified by the proposed AD are intended to prevent uncontained failure of the LPT 5th stage disk, due to incomplete blend repairs, resulting in in-flight shutdown and damage to the airplane.

DATES:

Comments must be received by October 29, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No.2001-NE-16-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: “[e-mail]”. 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 [phone]; fax [phone]. This information may be examined at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT:

Tara Goodman, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Office Park, Burlington, MA 01803-5299; telephone [phone], fax [phone].

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 2001-NE-16-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. 2001-NE-16-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

The FAA has received a report of an uncontained LPT 5th stage disk failure on a PW JT9D-7R4G2 turbofan engine that resulted in damage to the airplane and in-flight shutdown. The investigation into the cause of that failure revealed that the disk failure resulted from an incomplete blending of damage, previously caused by an LPT stage 4-5 tiebolt fracture. High-energy damage to the disk caused by a tiebolt fracture, if not completely removed by blending, may lead to disk cracking and fracture. Also, a review of the Engine Manual and the Standard Practices Operating Procedures for blending repairs indicates that these blending procedures may not ensure complete removal of all damaged material from the disks. This condition, if not corrected, could result in uncontained failure of the LPT 5th stage disk, due to incomplete blend repairs, resulting in in-flight shutdown and damage to the airplane.

Manufacturer's Service Information

The FAA has reviewed and approved the technical contents of PW service bulletin (SB) JT9D-7R4-72-574, Revision 1, dated June 26, 2001. That SB describes procedures for a one-time visual inspection of all PW JT9D-7R4 series LPT 5th stage disks for evidence of blend repairs and damage from fractured tiebolts in the forward and aft web and bore area, and disk removal from service based on the extent of damage.

FAA's Determination of an Unsafe Condition and Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other Pratt & Whitney JT9D-7R4 series turbofan engines of the same type design, the proposed AD would require a one-time visual inspection of PW JT9D-7R4 series LPT 5th stage disks for evidence of blend repairs in the forward and aft web and bore area. If a disk has any amount of blended or unblended damage in the web and bore area that was caused by a fractured tiebolt, or if a disk has five or more blended or unblended areas of damage by any cause, the disk must be removed from service. The actions would be required to be accomplished at the next separation of the LPT module from the engine after the effective date of this AD, in accordance with the service bulletin described previously.

Economic Impact

There are approximately 647 Pratt & Whitney (PW) JT9D-7R4 series turbofan engines of the affected design in the worldwide fleet. The FAA estimates that 151 engines installed on airplanes of U.S. registry would be affected by this proposed AD. The FAA also estimates that it would take approximately one work hour per engine to accomplish the proposed actions, and that the average labor rate is $60 per work hour. A replacement disk would cost approximately $145,260 per engine. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $21,943,320.

Regulatory Impact

This proposed rule 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 proposed rule.

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.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

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:

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:

Pratt & Whitney: Docket No. 2001-NE-16-AD.

Applicability

This airworthiness directive (AD) is applicable to Pratt & Whitney (PW) JT9D-7R4D, -7R4D1, -7R4E, -7R4E1, -7R4E4, -7R4G2, and 7R4H1 series turbofan engines with LPT 5th stage disks, part numbers (P/N's) 787905, 787905-001, and 798305 installed. These engines are installed on, but not limited to Airbus Industrie A300 and A310 series, and Boeing 747 and 767 series airplanes.

Note 1:

This 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 (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

Compliance with this AD is required as indicated at the next separation of the LPT module from the engine, unless already done.

To prevent uncontained failure of the low pressure turbine (LPT) 5th stage disk due to incomplete blend repairs, resulting in in-flight shutdown and damage to the airplane, do the following:

(a) Perform a one-time visual inspection for evidence of blend repairs of LPT 5th stage disks, P/N's 787905, 787905-001, and 798305 in accordance with the Accomplishment Instructions section of PW service bulletin (SB) JT9D-7R4-72-574, Revision 1, dated June 26, 2001.

(1) Remove from service those LPT 5th stage disks that were installed in engines that experienced a tiebolt fracture and are found with blended or unblended damage in the web and bore area, and replace with a serviceable part.

(2) Remove from service disks that have five or more blended or unblended damage areas by any cause, and replace with a serviceable part.

(b) After the effective date of this AD, do not install any LPT module that contains an LPT 5th stage disk, P/N 787905, 787905-001, or 798305 unless that disk has been inspected as specified in paragraph (a) of this AD.

Alternative Methods of Compliance

(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 (ECO). Operators must 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.

Issued in Burlington, Massachusetts, on August 22, 2001.

Donald Plouffe,

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