[Federal Register Volume 62, Number 113 (Thursday, June 12, 1997)]
[Rules and Regulations]
[Pages 32025-32027]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-14956]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-ANE-23-AD; Amendment 39-10047, AD 97-12-05]
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 supersedes Telegraphic AD T97-09-51 that currently
requires visual checks of the engine Debris Monitoring System (DMS)
sensor for bearing debris, and, if necessary, performing procedures for
additional maintenance actions. In addition, that AD requires replacing
Variable Speed Constant Frequency (VSCF) gearshaft flange ball bearings
that may incorporate rivets that are manufactured of improper material
with serviceable bearings. This action references a later revision of
the applicable Service Bulletin (SB) that includes additional engine
serial numbers; however, these changes do not affect the Applicability
or compliance requirements of this AD. This amendment is prompted by
the issuance of the new revision to the SB. The actions specified by
this AD are intended to prevent a VSCF gearshaft flange ball bearing
failure, which could result in an inflight engine shutdown.
DATES: Effective June 27, 1997.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of June 27, 1997.
Comments for inclusion in the Rules Docket must be received on or
before August 11, 1997.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), New England Region, Office of the Assistant Chief
Counsel, Attention: Rules Docket No. 97-ANE-23, 12 New England
Executive Park, Burlington, MA 01803-5299. Comments may also be sent
via the Internet using the following address: ``engineprop@faa.dot.gov''. 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; fax
(513) 672-8422, telephone (513) 672-8400 Ext. 114. This information may
be examined at the FAA, New England Region, Office of the Assistant
Chief 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 Golinski, Aerospace Engineer,
Engine Certification Office, FAA, Engine and Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803-5299; telephone (617)
238-7135, fax (617) 238-7199.
SUPPLEMENTARY INFORMATION: On April 22, 1997, the Federal Aviation
Administration (FAA) issued Telegraphic airworthiness directive (AD)
T97-09-51, applicable to General Electric Company (GE) GE90 series
turbofan engines, which requires visual checks of the engine Debris
Monitoring System (DMS) sensor for bearing debris, and, if necessary,
performing procedures for additional maintenance actions. In addition,
that AD requires replacing Variable Speed Constant Frequency (VSCF)
gearshaft flange ball bearings that may incorporate rivets that are
manufactured of improper material with serviceable bearings. That
action was prompted by reports of two recent failures of the Accessory
Gearbox (AGB) VSCF gearshaft flange ball bearing, Part Number (P/N)
1770M41P01. This ball bearing is installed on the VSCF gearshaft which
is located in the AGB and drives the Boeing 777 VSCF generator. The
VSCF generator is a backup power supply for the Boeing 777 airplane.
The ball bearing that failed is installed in GE90 AGBs, P/Ns 1650M71G03
and 1650M71G04. A third AGB configuration incorporates a different ball
bearing design and has no reported service problems. The bearing
failure investigation is ongoing; however, there is evidence that
suggests the failures may be attributed to bearing operation with
insufficient internal radial clearances that results in excessive ball
to cage pocket forces causing bearing distress and premature failure.
The investigation has also determined that a population of the VSCF
gearshaft ball bearings, P/N 1770M41P01, may contain improper cage
rivet material. Metallurgical evaluation of the rivets installed in the
two failed VSCF gearshaft flange ball bearings has confirmed both
bearings contained rivets manufactured from improper material. Results
of the engineering analysis and testing suggest the improper rivet
material may be a contributor to premature bearing distress when the
improper rivets are installed in a bearing that contains insufficient
internal radial clearance. That condition, if not corrected, could
result in a VSCF gearshaft flange ball bearing failure, which could
result in an inflight engine shutdown.
Since the issuance of that Telegraphic AD, GE has issued Revision
4, dated April 17, 1997, to Service Bulletin (SB) No. 72-283, which
adds additional engine serial numbers; however, these changes do not
affect the Applicability or compliance requirements of this AD. This AD
references this revised SB.
The FAA has reviewed and approved the technical contents of GE SB
No. 79-
[[Page 32026]]
011, dated April 9, 1997, that describes procedures for monitoring the
engine lubrication system for bearing debris, and, if necessary, the
procedures for additional maintenance actions; GE SB No. 72-280,
Revision 3, dated April 15, 1997, that describes procedures for
replacement of certain VSCF gearshaft flange ball bearings that may
incorporate improper rivet material; GE SB No. 72-283, Revision 4,
dated April 17, 1997, that describes the procedures for replacing the
4,500 pound inches gearshaft assembly used in AGBs, P/Ns 1650M71G03 and
1650M71G04, with the 3,500 pound inches gearshaft assembly used in the
AGB, P/N 1650M71G02; and GE SB No. 72-286, dated April 14, 1997, that
describes procedures for replacing the VSCF gearshaft assembly with a
VSCF gearshaft assembly containing a flange ball bearing with a select
fit internal radial clearance.
Since an unsafe condition has been identified that is likely to
exist or develop on other engines of this same type design, this AD
supersedes Telegraphic AD T97-09-51 to require, within 24 hours after
the effective date of this AD, a visual check of the engine DMS sensor
for bearing debris, and, if necessary, performing procedures for
additional maintenance actions. Thereafter, this AD requires visual
checks of the engine DMS sensor for bearing debris at staggered one-day
intervals for each affected engine on the Boeing 777 (inspecting each
engine every other day). In addition, this AD requires replacing VSCF
gearshaft flange ball bearings that may incorporate rivets that are
manufactured of improper material with serviceable bearings. Replacing
the VSCF gearshaft assembly in accordance with GE SB No. 72-283,
Revision 4, dated April 17, 1997, or GE SB No. 72-286, dated April 14,
1997, constitutes an acceptable alternative to the replacement of the
affected bearing.
This AD defines interim requirements to prevent a VSCF gearshaft
flange ball bearing failure. These requirements may be amended in
further rulemaking as additional information from the failure
investigation is obtained and corrective action is defined. The actions
are required to be accomplished in accordance with the SBs 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 97-ANE-23.'' 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:
97-12-05 General Electric Company: Amendment 39-10047. Docket No.
97-ANE-23-AD. Supersedes Telegraphic AD T97-09-51.
Applicability: General Electric Company (GE) GE90 series
turbofan engines with Accessory Gearboxes (AGBs) installed, Part
Numbers (P/Ns) 1650M71G03 and 1650M71G04. These engines are
installed on 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 (c) 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 prevent a Variable Speed Constant Frequency (VSCF) gearshaft
flange ball bearing failure, which could result in an inflight
engine shutdown, accomplish the following:
(a) Perform a visual check of the engine Debris Monitoring
System sensor for debris in accordance with paragraph 2(c) of the
[[Page 32027]]
Accomplishment Instructions of GE Service Bulletin (SB) No. 79-011,
dated April 9, 1997, as follows:
(1) For aircraft that have two engines installed incorporating
AGBs, P/N 1650M71G03 or 1650M71G04, accomplish the following:
(i) Perform an initial visual check on one of the engines
installed on the aircraft within 24 clock hours after the effective
date of this AD, and thereafter, visually check that engine every
other day, at intervals not to exceed 48 clock hours since last
visual check.
(ii) Perform an initial visual check on the engine not inspected
in accordance with paragraph (a)(1)(i) of this AD installed on the
same aircraft on the following day, not to exceed 24 clock hours
after the visual check of the engine checked in paragraph (a)(1)(i)
of this AD; thereafter, visually check this engine every other day
at intervals not to exceed 48 clock hours since last visual check.
(iii) The visual checks for both engines must be staggered at
one day intervals for each engine.
(2) For aircraft that have one of the two engines installed
incorporating AGBs, P/N 1650M71G03 or 1650M71G04, perform the
initial visual check on that engine within 24 clock hours after the
effective date of this AD, and thereafter, visually check that
engine every other day at intervals not to exceed 48 clock hours
since last visual check.
(3) If the visual check indicates that debris is present,
perform additional maintenance actions in accordance with paragraph
2(c) of the Accomplishment Instructions of GE SB No. 79-011, dated
April 9, 1997, prior to further flight.
(b) For engines that contain VSCF gearshaft flange ball bearings
that may incorporate rivets manufactured from improper material,
identified by serial numbers: 900-147, 900-149, 900-151, 900-106,
and 900-153, within 7 days after the effective date of this AD, and
for engines identified by serial numbers: 900-150, 900-156, 900-157,
900-158, prior to entry into revenue service, accomplish one of the
following:
(1) Remove from service VSCF gearshaft flange ball bearings and
replace with serviceable bearings in accordance with the
Accomplishment Instructions of GE SB No. 72-280, Revision 3, dated
April 15, 1997; or
(2) Remove and replace the 4,500 pound inches VSCF gearshaft
assembly with the 3,500 pound inches gearshaft assembly installed in
AGB, P/N 1650M71G02, in accordance with the Accomplishment
Instructions of GE SB No. 72-283, Revision 4, dated April 17, 1997.
Accomplishment of this option constitutes terminating action to the
inspection requirements of paragraph (a) of this AD; or
(3) Remove and replace the 4,500 pound inches VSCF gearshaft
assembly with the 4,500 pound inches gearshaft assembly containing
select fit internal radial clearance flange ball bearings, in
accordance with the Accomplishment Instructions of GE SB No. 72-286,
dated April 14, 1997.
(c) 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.
(d) 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 requirements of this AD can be accomplished.
(e) The actions required by this AD shall be accomplished in
accordance with the following GE SBs:
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Document No. Page Revision Date
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72-283........................ 1, 2 4 April 17, 1997.
3-10 Original March 12, 1997.
11, 12 1 March 20, 1997.
13 Original March 12, 1997.
Total Pages: 13.
72-280........................ 1, 2 3 April 15, 1997.
3-12 2 March 19, 1997.
Total Pages: 12.
72-286........................ 1-15 Original April 14, 1997.
Total Pages: 15.
79-011........................ 1-6 Original April 9, 1997.
Total Pages: 6.
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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; fax (513) 672-8422, telephone
(513) 672-8400 Ext. 114. Copies may be inspected at the FAA, New
England Region, Office of the Assistant Chief 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.
(f) This amendment supersedes Telegraphic AD T97-09-51, issued
April 22, 1997.
(g) This amendment becomes effective on June 27, 1997.
Issued in Burlington, Mass., on June 2, 1997.
Thomas A. Boudreau,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 97-14956 Filed 6-11-97; 8:45 am]
BILLING CODE 4910-13-U
