E6-5843. Airworthiness Directives; Pratt & Whitney PW4077D, PW4084D, 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). This proposed AD is for Pratt & Whitney (PW) PW4077D, PW4084D, PW4090, and PW4090-3 turbofan engines that were reassembled with certain previously used high pressure compressor (HPC) exit brush seal assembly parts and certain new or refurbished HPC exit diffuser air seal inner lands. This proposed AD would require replacing the HPC exit inner and outer brush seal packs with new brush seal packs, or replacing the HPC exit brush seal assembly with a new HPC exit brush seal assembly. This proposed AD results from a report of oil leaking into the high pressure turbine (HPT) interstage cavity and igniting, leading to an uncontained failure of the 2nd stage turbine air seal and engine in-flight shutdown. We are proposing this AD to prevent uncontained engine failure, damage to the airplane, and injury to passengers.

DATES:

We must receive any comments on this proposed AD by June 19, 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:

Antonio Cancelliere, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5213; 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-2006-24034; Directorate Identifier 2006-NE-05-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. The dockets include 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

In June 2005, a PW4090 engine installed on a Boeing 777 airplane experienced an uncontained HPT interstage air seal failure, penetrating the engine case. The investigation revealed that the primary failure of this event was a fractured HPC exit diffuser air seal. The inner land of the HPC exit diffuser air seal was fractured, causing oil leakage from the No. 3 bearing compartment and an internal oil fire. This oil fire elevated the temperature in the HPT cavity that led to the failure of the HPT interstage air seal. The engine build configuration of this event included a previously used HPC exit inner brush seal pack assembled with a refurbished outer seal pack. Root cause investigation continues to focus on the operating environment surrounding the HPC exit diffuser air seal location. Further analysis performed on the seal system indicates its sensitivity to unsteady airflow through the system under specific brush seal geometry and operating conditions. This unsteady airflow contributes to an increase of the dynamic stress level on the HPC exit diffuser air seal inner land, causing it to crack. Based on these results of the ongoing investigation, PW recommends the replacement of the inner brush seal pack when the HPC exit brush outer seal pack is replaced. Any oil escape resulting from a fractured HPC diffuser air seal has the potential to ignite and compromise the integrity of the 1st and 2nd stage HPT disk. A disk failure would cause high kinetic energy material to release and penetrate the engine casing and airplane fuselage. This condition, if not corrected, could result in uncontained engine failure, damage to the airplane, and injury to passengers.

Relevant Service Information

We have reviewed and approved the technical contents of PW Service Bulletin (SB) No. PW4G-112-A72-280, Revision 1, dated March 21, 2006. That SB applies to engines that were reassembled with a previously used HPC exit brush seal pack, part number (P/N) 50J894-01, and a new or refurbished HPC exit diffuser air seal inner land, P/N 55H869. That SB describes procedures for replacing the inner and outer brush seal packs on the HPC exit brush seal assemblies.

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 replacing the HPC exit inner and outer brush seal packs with new HPC exit inner and outer brush seal packs, or replacing the HPC exit brush seal assembly with a new HPC exit brush seal assembly. The proposed AD would require you to use the service information described previously to perform the HPC exit inner and outer brush seal pack replacements.

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 76 PW PW4077D, PW4084D, PW4090, and PW4090-3 turbofan engines installed on airplanes of U.S. registry. We also estimate that it would take about 9 work hours per engine to perform the proposed parts replacement, and that the average labor rate is $80 per work hour. Required parts would cost about $100,017 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $7,656,012.

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-2006-24034; Directorate Identifier 2006-NE-05-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by June 19, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Pratt & Whitney (PW) PW4077D, PW4084D, PW4090, and PW4090-3 turbofan engines that were:

(1) Reassembled with a previously used high pressure compressor (HPC) exit inner brush seal pack, part number (P/N) 50J894-01; and

(2) Reassembled with a new or refurbished HPC exit diffuser air seal inner land, P/N 55H869.

(d) These engines are installed on, but not limited to, Boeing 777 airplanes.

Unsafe Condition

(e) This AD results from a report of oil leaking into the high pressure turbine interstage cavity and igniting, leading to an uncontained failure of the 2nd stage turbine air seal and engine in-flight shutdown. We are issuing this AD to prevent uncontained engine failure, damage to the airplane, and injury to passengers.

Compliance

(f) You are responsible for having the actions required by this AD performed at the following compliance times, unless the actions have already been done.

(g) Replace the HPC exit inner and outer brush seal packs with new HPC exit inner and outer brush seal packs, or replace the HPC exit brush seal assembly with a new HPC exit brush seal assembly as follows:

(1) By 3,000 cycles-since-last-overhaul (CSLO) or by March 31, 2007, whichever occurs later; however

(2) If on March 31, 2007, the engine has not accumulated 3,000 CSLO, then by 3,000 CSLO, or December 31, 2008, whichever occurs first.

(h) Use the Accomplishment Instructions of PW Service Bulletin No. PW4G-112-A72-280, Revision 1, dated March 21, 2006, to do the inner and outer brush pack replacements.

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 13, 2006.

Francis A. Favara,

Manager, Engine and Propeller Directorate, Aircraft Certification Service.