Airworthiness Directives; General Electric Company GE90 Series Turbofan Engines

[Federal Register Volume 67, Number 14 (Tuesday, January 22, 2002)]
[Rules and Regulations]
[Pages 2801-2802]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-1453]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NE-32-AD; Amendment 39-12606; AD 2002-01-12]
RIN 2120-AA64


Airworthiness Directives; General Electric Company GE90 Series 
Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), that 
is applicable to General Electric Company (GE) GE90 series turbofan 
engines. This amendment requires removing from service high pressure 
turbine (HPT) interstage seals, identified by GE as the pre-life-
improved rotor (pre-LIR) configuration, and installing a new design, 
identified by GE as the life improved rotor (LIR) configuration seal. 
This amendment also requires a new lower life limit for the LIR 
configuration seal. This amendment is prompted by an uncontained engine 
failure which occured during a factory development engine ground test. 
The actions specified by this AD are intended to prevent failure of the 
HPT interstage seal that could result in an uncontained engine failure 
and damage to the airplane.

DATES: Effective date February 26, 2002.

ADDRESSES: This information may be examined, by appointment, at the 
Federal Aviation Administration (FAA), New England Region, Office of 
the Regional Counsel, 12 New England Executive Park, Burlington, MA; or 
at the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: John E. Golinski, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone: (781) 
238-7135; fax: (781) 238-7199.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an AD that is 
applicable to General Electric Company (GE) GE90 series turbofan 
engines was published in the Federal Register on September 27, 2001. 
That action proposed to require removing from service high pressure 
turbine (HPT) interstage seals, identified by GE as the pre-life-
improved rotor (pre-LIR) configuration, and installing a new design, 
identified by GE as the life improved rotor (LIR) configuration seal, 
and to require a new lower life limit for the LIR configuration seal.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comment received.
    One commenter requests that paragraph (c) of the proposal be 
revised or deleted. Paragraph (c) proposed to prohibit the installation 
of HPT interstage seal P/N's 1711M20P08, 1711M20P14, 1711M20P16, and 
1711M20P17 into any engine after the effective date of the AD. The 
commenter believes this requirement may result in an undue burden for 
lease pool engines since it would require the removal of an interstage 
seal that had considerable remaining life. The commenter believes there 
would be no unsafe condition in allowing continued operation of that 
seal up to the maximum number of cycles-since-new, or up to December 
31, 2006, the end date stated in the proposal.
    The FAA does not agree. The FAA believes the commenter's request is 
driven by the economic benefits that would be realized from commenter's 
lease pool engines. This pool of engines is a very small minority of 
the total GE90 engine fleet. If the commenter's request were adopted, 
however, the entire GE90 fleet would have no restrictions on the reuse 
of a pre-LIR HPT interstage seal, which is not the FAA's intent. The 
FAA believes that the minority of lease pool engines owned by the 
commenter can be addressed by the alternative methods of compliance 
process on a case-by-case basis if required.
    After careful review of the available data, including the comment 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule as proposed.

Economic Analysis

    There are approximately 232 GE90-76B, -77B, -85B, -90B, and -94B 
series turbofan engines of the affected design in the worldwide fleet. 
The FAA estimates that 36 engines installed on airplanes of U.S. 
registry, with one domestic operator, would be affected by this AD. The 
FAA estimates that the cost for replacing the pre-LIR HPT interstage 
seals is $536,340, based on an assumption of how many seals will be 
replaced prior to reaching the full retirement life. The FAA also 
estimates

[[Page 2802]]

that the LIR HPT interstage seal life reduction cost will be 
$3,396,820, and is based on the pro-rated costs of HPT interstage seals 
that will be removed due to the reduced life limit. Based on these 
figures, the total cost of the AD on U.S. operators is estimated to be 
$3,933,160.

Regulatory Analysis

    This final rule does not have federalism implications, as defined 
in Executive Order 13132, because it 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. Accordingly, 
the FAA has not consulted with state authorities prior to publication 
of this final rule.
    For the reasons discussed above, I certify that this action (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) if promulgated, 
will not have a significant economic impact, positive or negative, on a 
substantial number of small entities under the criteria of the 
Regulatory Flexibility Act. A final evaluation has been prepared for 
this action and it is contained in the Rules Docket. A copy of it may 
be obtained by contacting the Rules Docket at the location provided 
under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (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. Section 39.13 is amended by adding a new airworthiness directive 
to read as follows:

2002-01-12  General Electric Company: Amendment 39-12606. Docket No. 
2001-NE-32-AD.

    Applicability: This airworthiness directive (AD) is applicable 
to General Electric Company (GE) GE90-76B, -77B, -85B, -90B, and -
94B turbofan engines with high pressure turbine (HPT) interstage 
seals part numbers (P/N's) 1711M20P08, 1711M20P14, 1711M20P16, 
1711M20P17, and 1847M96P02 installed. These engines are installed 
on, but not limited to Boeing 777 airplanes.

    Note 1: This AD applies to each engine identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For engines that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (g) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Compliance with this AD is required as indicated, 
unless already done.
    To prevent failure of the HPT interstage seal that could result 
in an uncontained engine failure, and damage to the airplane, do the 
following:

Replacement of HPT Interstage Seals P/N's 1711M20P08, 1711M20P14, 
1711M20P16, and 1711M20P17

    (a) For GE90-76B, -77B, -85B, -90B engines with HPT interstage 
seals P/N's 1711M20P08, 1711M20P16, and 1711M20P17 installed, and 
GE90-76B and -77B engines with interstage seal P/N 1711M20P14 
installed, replace seals at next shop visit piece-part exposure with 
a serviceable HPT interstage seal, after the effective date of this 
AD, but not to exceed 4,800 cycles-since-new (CSN), or before 
December 31, 2006, whichever occurs earlier.
    (b) For GE90-85B and -90B engines with HPT interstage seal P/N 
1711M20P14 installed, replace seal at next shop visit piece-part 
exposure with a serviceable HPT interstage seal, after the effective 
date of this AD, but not to exceed 2,800 CSN, or before December 31, 
2006, whichever occurs earlier.
    (c) After the effective date of this AD, do not install any HPT 
interstage seal P/N's 1711M20P08, 1711M20P14, 1711M20P16, and 
1711M20P17 into an engine.

Reduced Life Limit

    (d) For engines with HPT interstage seals P/N 1847M96P02 
installed, remove engine from service before exceeding the reduced 
cyclic life limit of 3,500 CSN.
    (e) This AD establishes a new cyclic life limit for HPT 
interstage seal, P/N 1847M96P02. Except as provided in paragraph (g) 
of this AD, no alternate life limits for this part may be approved.

Definition

    (f) For the purpose of this AD, a shop visit piece-part exposure 
is defined as an engine removal for maintenance that cannot be 
performed while installed on the airplane, and that the HPT 
interstage seal is completely disassembled when done in accordance 
with the disassembly instructions of the engine manual.

Alternative Methods of Compliance

    (g) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Engine Certification Office (ECO). 
Operators must submit their request through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, ECO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the ECO.

Special Flight Permits

    (h) Special flight permits may be issued in accordance with 
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
21.197 and 21.199) to operate the airplane to a location where the 
requirements of this AD can be done.

Effective Date

    (i) This amendment becomes effective on February 26, 2002.

    Issued in Burlington, Massachusetts, on January 14, 2002.
Thomas Boudreau,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 02-1453 Filed 1-18-02; 8:45 am]
BILLING CODE 4910-13-U

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