Airworthiness Directives; Pratt & Whitney (PW) PW4164, PW4168, and PW4168A 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 PW PW4164, PW4168, and PW4168A turbofan engines with certain low pressure turbine (LPT) stage 4 disks, part number (P/N) 51N404, installed. This proposed AD would require removing certain LPT stage 4 disks, listed by serial number at the next piece-part exposure or within 7,500 cycles-since-new (CSN), whichever occurs first. This proposed AD results from a report of improperly manufactured LPT stage 4 disks. We are proposing this AD to prevent an uncontained engine failure due to low-cycle fatigue (LCF), which could result in damage to the airplane.

DATES:

We must receive any comments on this proposed AD by July 20, 2007.

ADDRESSES:

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

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government -wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590-0001.
• Fax: (202) 493-2251.
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

You may examine the comments on this proposed AD in the AD docket on the Internet at http://dms.dot.gov.

FOR FURTHER INFORMATION CONTACT:

V. Rose Len, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; telephone (781) 238-7772; fax (781) 238-7199.

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-2007-27230; Directorate Identifier 2007-NE-04-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://dms.dot.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 DOT Web site, anyone can find and read the comments in any of our dockets, including 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) or you may visit http://dms.dot.gov .

Examining the AD Docket

You may examine the docket that contains the proposal, any comments received and, any final disposition in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone (800) 647-5227) is located on the plaza level of the Department of Transportation Nassif Building at the street address stated in ADDRESSES. Comments will be available in the AD docket shortly after the Docket Management Facility receives them.

Discussion

On September 29, 2006, we received a report of 16 LPT stage 4 disks, P/N 51N404, manufactured with an improper material process. The disks were not properly heat treated during the manufacturing process. The manufacturer solution-heat treated the disks for one hour instead of the four hours required. We believe this manufacturing discrepancy will result in reduced LCF properties for the disks. Operating the affected disks to the certified life limit could result in uncontained failure of the disk due to LCF. Although we have received no reports of disk separations, this condition, if not corrected, could result in the disk separating from the engine due to LCF, which could result in 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 require removing certain LPT stage 4 disks, P/N 51N404, listed by serial number in the proposed AD, at the next piece-part exposure, or within 7,500 CSN, whichever occurs first.

Costs of Compliance

We estimate that this proposed AD would affect 11 engines installed on airplanes of U.S. registry. We also estimate that it would take about 250 work-hours per engine to perform the proposed action, if not done at piece-part exposure, and that the average labor rate is $80 per work-hour. Required parts would cost about $186,288 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $2,269,168.

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.