[Federal Register Volume 66, Number 188 (Thursday, September 27, 2001)]
[Proposed Rules]
[Pages 49326-49328]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-24274]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NE-32-AD]
RIN 2120-AA64


Airworthiness Directives; General Electric Company GE90 Series 
Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The Federal Aviation Administration (FAA) proposes to adopt a 
new airworthiness directive (AD) that is applicable to General Electric 
Company (GE) GE90 series turbofan engines. This proposal would 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. This proposal would also 
require a new lower life limit for the LIR configuration seal. This 
proposal is prompted by an uncontained engine failure which occured 
during a factory development engine ground test. The actions specified 
by the proposed 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: Comments must be received by November 26, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No.2001-NE-32-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: [email protected] 
Comments sent via the Internet must contain the docket number in the 
subject line. Comments may be inspected at this location between 8:00 
a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. The 
service information referenced in the proposed rule may be obtained 
from General Electric Company via Lockheed Martin Technology Services, 
10525 Chester Road, Suite C, Cincinnati, OH 45215; telephone: (513) 
672-8400, fax: (513) 672-8422. This information may be examined at the 
FAA, New England Region, Office of the Regional Counsel, 12 New England 
Executive Park, Burlington, MA.

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

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this action may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2001-NE-32-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRM's

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, New England Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 2001-NE-32-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    In September, 2000 a GE90 factory development engine experienced an 
uncontained failure of the HPT interstage seal during an engineering 
ground test. The failure occurred on the current configuration HPT 
interstage seal, identified as the LIR configuration. The LIR 
configuration HPT interstage seal was introduced as part of an HPT 
product improvement package. The

[[Page 49327]]

earlier production configuration HPT interstage seal, identified as the 
pre-LIR interstage seal, part numbers (P/N's) are 1711M20P08, 
1711M20P14, 1711M20P16, and 1711M20P17. The LIR HPT interstage seal P/N 
is 1847M96P02.
    GE initiated an investigation to understand the root cause of the 
failure and to define the necessary field containment and corrective 
actions. As part of the investigation GE initiated inspections on pre-
LIR and LIR HPT interstage seals that would provide additional data to 
support the failure investigation and assist in the determination of 
the necessary field containment actions. These inspections identified 
four pre-LIR interstage seals and one LIR interstage seal that had 
confirmed cracks.
    The failure investigation consisted of analysis and testing to 
identify the failure modes of the pre-LIR and LIR HPT interstage seals. 
In addition, GE instituted an on-wing inspection program of pre-LIR 
seals to acquire additional data to support the investigation. To 
prevent pre-LIR HPT interstage seal failures, GE issued a service 
bulletin that removes pre-LIR HPT interstage seals from service and 
replaces them with improved LIR HPT interstage seals that are not 
susceptible to the same failure modes. This AD proposes scheduled 
replacement of pre-LIR HPT interstage seals.
    As a result of the root cause investigation into the failure of the 
LIR HPT interstage seal and the investigation of the cracked HPT seals 
identified by the inspection program, GE determined the root cause of 
the cracks in the forward retainer tip area of the LIR HPT interstage 
seal were attributed to exposure to higher than anticipated operating 
temperatures. This causes a reduction of the low cycle fatigue 
properties of the material in this local area, which results in crack 
initiation. Analysis concludes that a reduction of the life limit for 
the LIR HPT interstage seal P/N 1847M96P02 is required. GE is in the 
process of incorporating design enhancements that will provide improved 
cooling in the forward retainer tip area that may allow for a life 
limit increase at some future date. This condition, if not corrected, 
could result in failure of the HPT interstage seal, uncontained engine 
failure, and damage to the airplane.

FAA's Determination of an Unsafe Condition and Proposed Actions

    Since an unsafe condition has been identified that is likely to 
exist or develop on other GE90 series turbofan engines of the same type 
design, the proposed AD would require scheduled replacement of HPT 
interstage seal P/N's 1711M20P08, 1711M20P14, 1711M20P16, and 
1711M20P17 with a serviceable HPT interstage seal. This proposed AD 
would also establish a new, lower life limit of 3,500 cycles-since-new 
for HPT interstage seal P/N 1847M96P02. The actions would be required 
to be accomplished in accordance with the service bulletin described 
previously.

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 proposed 
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 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 proposed AD on U.S. 
operators is estimated to be $3,933,160.

Regulatory Analysis

    This proposed 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 proposed rule.
    For the reasons discussed above, I certify that this 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) 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 copy of the draft 
regulatory evaluation prepared for this action 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.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 the following new 
airworthiness directive:

General Electric Company: 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

[[Page 49328]]

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 accomplished 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 
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
21.197 and 21.199) to operate the aircraft to a location where the 
requirements of this AD can be accomplished.


    Issued in Burlington, Massachusetts, on September 20, 2001.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 01-24274 Filed 9-26-01; 8:45 am]
BILLING CODE 4910-13-U