AD Amdt-39-10047

[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 [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[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: ``<a href="/cdn-cgi/l/email-protection#bf8692dedb92b5dad1d8d6d1dacfcdd0cfffd9dede91dbd0cb91d8d0c9">9-ad-
<span class="__cf_email__" data-cfemail="7f1a111816111a0f0d100f3f191e1e511b100b51181009">[email&#160;protected]</span></a>''. 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