2010-27607. Airworthiness Directives; Pratt & Whitney (PW) Models PW4074 and PW4077 Turbofan Engines

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for PW PW4074 and PW4077 turbofan engines with 15th stage high-pressure compressor (HPC) disks, part number (P/N) 55H615, installed. This proposed AD would require removing the 15th stage HPC disk within 12,000 cycles since new (CSN) or, for any disks that exceed 12,000 CSN after the effective date of this AD using a drawdown plan that includes a borescope inspection (BSI) or eddy current inspection (ECI) of the rim for cracks. This proposed AD results from multiple shop findings of cracked 15th stage HPC disks. We are proposing this AD to prevent cracks from propagating into the bolt hole, which could result in a failure of the 15th stage HPC disk, uncontained engine failure, and damage to the airplane.

DATES:

We must receive any comments on this proposed AD by January 3, 2011.

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].

Contact Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone [phone]; fax [phone], for a copy of the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

James Gray, 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-2010-1095; Directorate Identifier 2009-NE-40-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

We have received reports of multiple shop findings of cracked 15th stage HPC disks that required removing the disks from service. As of June 30, 2010, 53 disks with cracks in the front rail of the load and lock slots have been reported. Engineering investigation determined that the initiation was the result of thermal mechanical fatigue. Three of the disks had cracks that propagated radially into the bolt holes. These cracks could propagate further and lead to failure of the disk.

This condition, if not corrected, could result in a failure of the 15th stage HPC disk, uncontained engine failure, and damage to the airplane.

Relevant Service Information

We have reviewed and approved the technical contents of PW Service Bulletin (SB) PW4G-112-72-309, Revision 1, dated July 1, 2010, that describes procedures for performing a BSI or ECI for cracks in the front rail of the outer rim of the 15th stage HPC disk.

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 require removing the 15th stage HPC disk before 12,000 CSN, or for any disks that exceed 12,000 CSN after the effective date of this AD using a drawdown plan that includes a BSI or ECI of the rim for cracks. The proposed AD would require you to use the service information described previously to perform these actions.

Interim Action

These actions are interim actions and we may take further rulemaking actions in the future.

Costs of Compliance

We estimate that this proposed AD would affect 44 engines installed on airplanes of U.S. registry. Prorated parts would cost about $66,000 per 15th stage HPC disk. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $2,904,000.

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
• Incorporation by reference
• 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-2010-1095; Directorate Identifier 2009-NE-40-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by January 3, 2011.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Pratt & Whitney (PW) PW4074 and PW4077 turbofan engines with 15th stage high-pressure compressor (HPC) disks, part number (P/N) 55H615, 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 multiple shop findings of cracked 15th stage HPC disks. We are issuing this AD to prevent cracks from propagating into the bolt holes of the 15th stage HPC disk, which could result in a failure of the 15th stage HPC disk, uncontained engine failure, and 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) For 15th stage HPC disks that have 9,865 or fewer cycles since new (CSN) on the effective date of this AD, remove the disk from service before accumulating 12,000 CSN.

(g) For 15th stage HPC disks that have accumulated more than 9,865 CSN on the effective date of this AD, do the following:

(1) Remove the disk from service at the next piece-part exposure above 12,000 CSN, not to exceed 2,135 cycles-in-service (CIS) after the effective date of this AD.

(2) For 15th stage HPC disks that are installed in the engine and exceed 12,000 CSN, perform a borescope inspection (BSI) or eddy current inspection (ECI):

(i) Within 2,400 cycles-since-last fluorescent penetrant inspection or ECI, or

(ii) Within 1,200 cycles-since-last BSI, or

(iii) Within 55 cycles-in-service (CIS) after the effective date of this AD, whichever is latest.

(3) If you see a suspected crack using a BSI from paragraph (g)(2) of this AD, but can't visually confirm a crack, perform an ECI within 5 CIS after the BSI.

(4) If you find a crack using any inspection, remove the disk from service before further flight.

(h) Use paragraph 1.A. or 1.B. of the Accomplishment Instructions “For Engines Installed on the Aircraft” or 1.A. or 1.B. of the Accomplishment Instructions “For Engines Removed from the Aircraft,” of PW Service Bulletin PW4G-112-72-309, Revision 1, dated July 1, 2010 to perform the inspections.

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) Contact James Gray, 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.

(k) Pratt & Whitney Service Bulletin PW4G-112-72-309 Revision 1, dated July 1, 2010, pertains to the subject of this AD. Contact Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone [phone]; fax [phone], for a copy of this service information.

Issued in Burlington, Massachusetts, on October 26, 2010.

Karen M. Grant,

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