[Federal Register Volume 71, Number 75 (Wednesday, April 19, 2006)]
[Proposed Rules]
[Pages 20042-20044]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-5843]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-24034; Directorate Identifier 2006-NE-05-AD]
RIN 2120-AA64


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).

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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: (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 can get the service information identified in this proposed AD 
from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone 
(860) 565-8770; fax (860) 565-4503.
    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 (781) 238-7751; 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-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

[[Page 20043]]

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 (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

    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.


Sec.  39.13  [Amended]

    2. The FAA amends Sec.  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

[[Page 20044]]

    (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.
[FR Doc. E6-5843 Filed 4-18-06; 8:45 am]
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