Airworthiness Directives; General Electric Company GE90 Series Turbofan Engines

[Federal Register Volume 63, Number 134 (Tuesday, July 14, 1998)]
[Rules and Regulations]
[Pages 37761-37763]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-18647]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-17-AD; Amendment 39-10654; AD 98-15-03]
RIN 2120-AA64


Airworthiness Directives; General Electric Company GE90 Series 
Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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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 action requires initial and repetitive eddy current 
inspections (ECI) for cracks in the high pressure compressor (HPC) 
stage 2-6 spool, and, if necessary, replacement with serviceable parts. 
This amendment is prompted by reports of cracks in the stage 3-4 and 
stage 4-5 interstage seal teeth and spacer arms. The actions specified 
in this AD are intended to identify cracks in the HPC stage 2-6 spool, 
which could result in an uncontained engine failure and damage to the 
aircraft.

DATES: Effective July 29, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of July 29, 1998.
    Comments for inclusion in the Rules Docket must be received on or 
before September 14, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 98-ANE-17-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ad-
[email protected]''. Comments sent via the Internet must contain 
the docket number in the subject line.
    The service information referenced in this AD may be obtained from 
General Electric Technical Services, Attention: Leader for 
distribution/ microfilm, 10525 Chester Road, Cincinnati, OH 45215; 
telephone (513) 672-8400 Ext. 130, 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; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Ian Dargin, Aerospace Engineer, Engine 
Certification Office, FAA, Engine and Propeller Directorate, 12 New 
England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-
7178, fax (781) 238-7199.

SUPPLEMENTARY INFORMATION: The Federal Aviation Administration (FAA) 
has received reports of cracked high pressure compressor (HPC) stage 2-
6 spools installed on General Electric Company (GE) GE90-76B/ -77B/ -
85B/ -90B/ -92B series turbofan engines. There have been 10 HPC spools 
found with cracks. The investigation into the cause of the cracking is 
ongoing; however, the FAA has determined that the HPC stage 2-6 spool 
may develop cracks in the stage 3-4 and stage 4-5 interstage seal teeth 
that could propagate into the stage 3-4 and stage 4-5 spacer arms, aft 
of the seal teeth. This AD requires inspection of the spacer arm aft of 
the seal teeth and also includes an inspection requirement for the 
spacer arm forward of the seal teeth that provides additional data to 
support the investigation and mitigates the risk of an HPC stage 2-6 
spool failure from a crack propagating into the spacer arm forward of 
the seal teeth. The FAA has determined the most likely cause of crack 
initiation is due to areas of heat affected zone in the seal teeth that 
is the result of excessive heat generated when

[[Page 37762]]

the rotating seal teeth rub into the static honeycomb material. This 
condition, if not corrected, could result in HPC stage 2-6 spool 
cracking, which could result in an uncontained engine failure and 
damage to the aircraft.
    The FAA has reviewed and approved the technical contents of GE 
Alert Service Bulletin (ASB) No. 72-A357, Revision 2, dated April 21, 
1998, that describes procedures for on-wing eddy current inspection 
(ECI) for cracks in the HPC stage 2-6 spool spacer arm forward and aft 
of the stage 3-4 and stage 4-5 interstage seal teeth, and GE Service 
Bulletin (SB) No. 72-352, Revision 2, dated March 31, 1998, that 
describes procedures for ECI of stage 3-4 and stage 4-5 interstage seal 
teeth.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other engines of the same type design, this AD is 
being issued to identify cracks in the HPC stage 2-6 spool, which could 
result in an uncontained engine failure and damage to the aircraft. 
This AD requires:
    (1) Initial and repetitive on-wing ECI for cracks in the HPC stage 
2-6 spool spacer arms forward and aft of the stage 3-4 and stage 4-5 
interstage seal teeth, and, if necessary, replacement with a 
serviceable engine.
    (2) A shop level ECI for cracks in the HPC stage 2-6 spool stage 3-
4 and stage 4-5 interstage seal teeth, and, if necessary, replacement 
with serviceable parts.
    Since this investigation is ongoing, further rulemaking may be 
necessary. The actions are required to be accomplished in accordance 
with the service documents described previously.
    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-ANE-17-AD.'' The postcard will be date stamped and 
returned to the commenter.
    The regulations adopted herein will not have substantial direct 
effects 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. Therefore, in 
accordance with Executive Order 12612, it is determined that this final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and is not a ``significant regulatory action'' 
under Executive Order 12866. It has been determined further that this 
action involves an emergency regulation under DOT Regulatory Policies 
and Procedures (44 FR 11034, February 26, 1979). If it is determined 
that this emergency regulation otherwise would be significant under DOT 
Regulatory Policies and Procedures, a final regulatory evaluation will 
be prepared and placed in the Rules Docket. A copy of it, if filed, may 
be obtained from the Rules Docket at the location provided under the 
caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, 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 the following new 
airworthiness directive:

98-15-03  General Electric Company: Amendment 39-10654. Docket 98-
ANE-17-AD.

    Applicability: General Electric Company (GE) GE90-76B/ -77B/ -
85B/ -90B/ -92B series turbofan engines, with high pressure 
compressor (HPC) stage 2-6 spools, Part Numbers 350-005-761-0, 350-
005-765-0, 350-005-769-0, 350-005-770-0, or 350-005-771-0, 
installed. These engines are installed on but not limited to Boeing 
777 aircraft.

    Note 1: This airworthiness directive (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 (d) 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: Required as indicated, unless accomplished 
previously.
    To identify cracks in the high pressure compressor (HPC) stage 
2-6 spool, which could result in an uncontained engine failure and 
damage to the aircraft, accomplish the following:
    (a) Perform initial and repetitive on-wing eddy current 
inspections (ECI) for cracks in HPC stage 2-6 spool spacer arms in 
accordance with GE Alert Service Bulletin (ASB) No. 72-A357, 
Revision 2, dated April 21, 1998.
    (1) Perform inspections of the spacer arm forward and aft of the 
stage 3-4 and 4-5 seal teeth as follows:
    (i) Perform the initial inspection prior to exceeding 500 cycles 
since new (CSN).
    (ii) Thereafter, inspect at intervals not to exceed 250 cycles 
in service (CIS) since last inspection.
    (2) Remove the engine from service if the ECI reveals a spool 
with a crack indication and replace with a serviceable engine prior 
to further flight.
    (b) Perform initial and repetitive ECI for cracks in the HPC 2-6 
spool stage 3-4 and

[[Page 37763]]

stage 4-5 interstage seal teeth during each shop visit as defined in 
paragraph (c) of this AD, and if necessary, replace with serviceable 
parts prior to returning the engine to revenue service, in 
accordance with GE Service Bulletin (SB) No. 72-352, Revision 2, 
dated March 31, 1998.
    (c) For the purpose of this AD, an engine shop visit is defined 
as any time an engine has maintenance performed that involves 
separation of a major engine flange (such as removal of an LPT 
module or HPC ``top case'').
    (d) 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. 
Operators shall submit their requests through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, Engine Certification Office.

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

    (e) Special flight permits may be issued in accordance with 
sections 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 inspection requirements of this AD can be accomplished.
    (f) The actions required by this AD shall be done in accordance 
with the following GE service documents:

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               Document Number                    Pages      Revision                     Date                  
----------------------------------------------------------------------------------------------------------------
SB No. 72-352................................         1-32           2  March 31, 1998.                         
    Total pages: 32                                                                                             
ASB No. 72-A357..............................         1-30           2  April 21, 1998.                         
    Total pages: 30                                                                                             
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This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from General Electric Technical Services, 
Attention: Leader for distribution/microfilm, 10525 Chester Road, 
Cincinnati, OH 45215; telephone (513) 672-8400 Ext. 130, fax (513) 
672-8422. Copies may be inspected at the 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.
    (g) This amendment becomes effective on July 29, 1998.

    Issued in Burlington, Massachusetts, on July 6, 1998.
Jay J. Pardee,
Manager, Engine and Propeller Directorate,
Aircraft Certification Service.
[FR Doc. 98-18647 Filed 7-10-98; 9:29 a.m.]
BILLING CODE 4910-13-P

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