E7-19927. Airworthiness Directives; Pratt & Whitney PW4090 and PW4090-3 Turbofan Engines

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for Pratt & Whitney (PW) PW4090 and PW4090-3 turbofan engines with front turbine hub, part number (P/N) 53L601, installed. This proposed AD would reduce the published life limit of those front turbine hubs from 12,000 cycles-since-new (CSN) to 9,370 CSN. This proposed AD would also remove from service those front turbine hubs using a drawdown schedule. This proposed AD results from PW updating the low-cycle-fatigue (LCF) life analysis for front turbine hubs, P/N 53L601. We are proposing this AD to prevent an uncontained failure of the front turbine hub, resulting in an in-flight engine shutdown and possible damage to the airplane.

DATES:

We must receive any comments on this proposed AD by December 10, 2007.

ADDRESSES:

Use one of the following addresses to comment on this proposed AD.

• Federal eRulemaking Portal: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility: U.S. Department of Transportation, 1200 New Jersey Avenue, SE., West Building Ground Floor, Room W12-140, Washington, DC 20590-0001.
• Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
• Fax: [phone].

FOR FURTHER INFORMATION CONTACT:

Mark Riley, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; e-mail: [e-mail], telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send us any written relevant data, views, or arguments regarding this proposal. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2007-29110; Directorate Identifier 2007-NE-35-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of the Web site, anyone can find and read the comments in any of our dockets, including, if provided, the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78).

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Operations office (telephone [phone]) is the same as the Mail address provided in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

Discussion

PW Engineering updated their life analysis for the front turbine hub, P/N 53L601, to incorporate new temperature data in the hub aft cavity area. The revised cavity temperatures cause higher than anticipated stress levels in the anti-rotation slots of the front turbine hub. This results in a reduced published LCF life limit from 12,000 CSN to 9,370 CSN. This condition, if not corrected, could result in uncontained engine failure resulting in an in-flight engine shutdown and possible damage to the airplane.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other products of this same type design. We are proposing this AD, which would:

• Reduce the published life limit of front turbine hub, P/N 53L601, from 12,000 CSN to 9,370 CSN; and
• Remove from service those front turbine hubs using a drawdown schedule.

Costs of Compliance

We estimate that this proposed AD would affect 94 engines installed on airplanes of U.S. registry. We also estimate that it would take about 101 work-hours per engine to perform the proposed actions, and that the average labor rate is $80 per work-hour. The prorated cost due to a life reduction from 12,000 CSN to 9,370 CSN for the front turbine hub is about $66,460 per engine. Based on these figures, we estimate the cost of the proposed AD on U.S. operators to be $6,247,240.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.

For the reasons discussed above, I certify that the proposed AD:

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. Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD. You may get a copy of this summary at the address listed under ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Under the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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. The FAA amends § 39.13 by adding the following new airworthiness directive:

Pratt & Whitney: Docket No. FAA-2007-29110; Directorate Identifier 2007-NE-35-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by December 10, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Pratt & Whitney (PW) PW4090 and PW4090-3 turbofan engines with front turbine hub part number (P/N) 53L601, installed. These engines are installed on, but not limited to, Boeing 777-200 series and 777-300 series airplanes.

Unsafe Condition

(d) This AD results from PW updating the low-cycle-fatigue (LCF) life analysis for front turbine hubs, P/N 53L601. We are proposing this AD to prevent an uncontained failure of the front turbine hub, resulting in an in-flight engine shutdown and possible damage to the airplane.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified unless the actions have already been done.

(f) Remove front turbine hubs, P/N 53L601, from service and install a serviceable front turbine hub, as follows:

(1) For front turbine hubs that have accumulated fewer than 3,370 cycles-since-new (CSN) on the effective date of this AD, remove from service before the hub accumulates 9,370 CSN.

(2) For front turbine hubs that have accumulated 3,370 or more CSN, but fewer than 9,370 CSN on the effective date of this AD, do the following:

(i) For engines that have an engine shop visit (ESV) before the front turbine hub accumulates 9,370 CSN, remove the front turbine hub from service before the hub accumulates 9,370 CSN.

(ii) For engines that do not have an ESV before the front turbine hub accumulates 9,370 CSN, remove the front turbine hub from service at the next ESV, or before the hub accumulates an additional 6,000 cycles-since-last high pressure turbine overhaul, whichever occurs first, but not to exceed 12,000 CSN.

(3) For front turbine hubs that have accumulated 9,370 or more CSN on the effective date of this AD, remove the front turbine hub from service at the next ESV, or before the hub accumulates 12,000 CSN, whichever occurs first.

(g) This AD establishes a new reduced published life limit for the PW4090 turbine front hub, P/N 53L601, of 9,370 CSN, which is published in Chapter 05, Time Limits Section 05-10-01, of the PW4000 Series Engine Shop Manual, P/N 51A751. The following conditions also apply:

(1) Except as provided in paragraphs (f)(2)(ii) and (f)(3) of this AD, no alternative retirement lives may be approved for the PW4090 front turbine hub, P/N 53L601.

(2) After the effective date of this AD, PW4090 front turbine hub, P/N 53L601, may not be installed or reinstalled on an engine if the hub has accumulated more than 9,370 CSN.

(h) For the purposes of this AD, an “engine shop visit” is:

(1) The induction of an engine into the shop for maintenance involving the separation of any major mating engine flange, except that for the separation of engine flanges solely for the purposes of transportation without subsequent engine maintenance does not constitute an engine shop visit; or

(2) The removal of a disk or spool.

Alternative Methods of Compliance

(i) The Manager, Engine Certification Office, has the authority to approve alternative methods of compliance for this AD if requested using the procedures found in 14 CFR 39.19.

Related Information

(j) Information on an approved front turbine hub rework procedure for increased life is available from the manufacturer. See Pratt & Whitney Service Bulletin PW4G-112-72-290, dated July 2, 2007. The reworked front turbine hub, P/N 53L601-001, is not affected by this AD.

(k) Contact Mark Riley, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; e-mail: [e-mail], telephone [phone]; fax [phone], for more information about this AD.

Issued in Burlington, Massachusetts, on October 2, 2007.

Peter A. White,

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