06-3922. Airworthiness Directives; Pratt & Whitney JT9D-7R4G2 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) JT9D-7R4G2 turbofan engines. This proposed AD would require replacing the old configuration 2nd stage high pressure turbine (HPT) air seal assembly with a new design 2nd stage HPT air seal assembly that increases cooling air flow. This proposed AD results from a report of an uncontained failure of the 2nd stage air seal assembly, caused by the air seal assembly brace disengaging from the air seal, due to insufficient cooling air flow. We are proposing this AD to prevent uncontained failure of the 2nd stage HPT air seal assembly, leading to engine in-flight shutdown and damage to the airplane.

DATES:

We must receive any comments on this proposed AD by June 26, 2006.

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: [phone].
• 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 can get the service information identified in this proposed AD from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone [phone]; fax [phone].

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:

Kevin Donovan, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; 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-2006-23742; Directorate Identifier 2005-NE-53-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 DOT Docket Office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone [phone]) 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

We have received two reports of failure of the 2nd stage HPT air seal assembly, part number (P/N) 815097, installed in JT9D-7R4G2 turbofan engines. One of those failures was uncontained. We have also received reports of damage found during HPT module disassembly, such as cracked knife-edge seals, cracked antirotation slots, and brace gaps over limits, on 2nd stage HPT air seal assemblies.

The old configuration 2nd stage HPT air seal assembly has a brace that can disengage and move radially, causing excessive rubbing of the air seal's knife edge against the static honeycomb seal. This rubbing leads to local excessive temperatures, cracks, thinning of the barrel of the 2nd stage HPT air seal assembly, and separation of material. The brace disengages from the air seal due to excessive buckling stress in the brace. The buckling stress is caused by the thermal interaction of the 2nd stage HPT air seal assembly and its constraining rotors. This thermal interaction causes higher-than-predicted temperatures leading to the brace disengaging. This condition, if not corrected, could result in uncontained failure of the 2nd stage HPT air seal assembly, leading to engine in-flight shutdown and damage to the airplane.

Relevant Service Information

We have reviewed and approved the technical contents of PW Alert Service Bulletin JT9D-7R4-A72-596, dated September 15, 2005. That Alert Service Bulletin describes procedures for replacing 2nd stage HPT air seal assembly, P/N 815097, with a new configuration 2nd stage HPT air seal assembly that increases cooling air flow, either by installing a new 2nd stage air seal assembly or modifying the old configuration 2nd stage HPT seal assembly.

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 at the next HPT module overhaul, replacing the 2nd stage HPT air seal assembly, P/N 815097, with a new configuration 2nd stage HPT air seal assembly that increases cooling air flow, either by installing a new 2nd stage air seal assembly or modifying the old configuration 2nd stage seal assembly. The proposed AD would require you to use the service information described previously to perform these actions.

Costs of Compliance

We estimate that this proposed AD would affect 176 PW JT9D-7R4G2 turbofan engines installed on airplanes of U.S. registry. We also estimate that it would take about 64 workhours per engine to perform the proposed actions, and that the average labor rate is $80 per workhour. Required parts would cost about $5,400 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $1,851,520.

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 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. 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. See the ADDRESSES section for a location to examine the regulatory evaluation.

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-2006-23742; Directorate Identifier 2005-NE-53-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by June 26, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Pratt & Whitney (PW) JT9D-7R4G2 turbofan engines. These engines are installed on, but not limited to, Boeing 747-200B, -200C, -200F, and -300 airplanes.

Unsafe Condition

(d) This AD results from a report of an uncontained failure of the 2nd stage air seal assembly, caused by the air seal assembly brace disengaging from the air seal, due to insufficient cooling air flow. We are issuing this AD to prevent uncontained failure of the 2nd stage high pressure turbine (HPT) air seal assembly, leading to engine in-flight shutdown and damage to the airplane.

Compliance

(e) You are responsible for having the actions required by this AD performed at the next HPT module exposure after the effective date of this AD, unless the actions have already been done.

(f) Replace the 2nd stage HPT air seal assembly, part number 815097, with a new configuration 2nd stage HPT air seal assembly that increases cooling air flow, either by installing a new 2nd stage air seal assembly, or modifying the old configuration 2nd stage HPT seal assembly.

(g) Use the Accomplishment Instructions of PW Alert Service Bulletin JT9D-7R4-A72-596, dated September 15, 2005, to do the replacement.

Definition

(h) For the purposes of this AD, an HPT module exposure is when the 1st stage HPT rotor and 2nd stage HPT rotor are removed from the HPT case, making the 2nd stage HPT vanes and 2nd stage HPT air seal assembly accessible in the HPT case.

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) None.

Issued in Burlington, Massachusetts, on April 19, 2006.

Thomas A. Boudreau,

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