AD 2001-12-20

[Federal Register Volume 66, Number 120 (Thursday, June 21, 2001)]
[Rules and Regulations]
[Pages 33166-33168]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 01-15446]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NE-30-AD; Amendment 39-12276; AD 2001-12-20]
RIN 2120-AA64


Airworthiness Directives; General Electric Company (GE) CF6-50 
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) CF6-50 turbofan engines. 
This amendment requires removal of old high pressure compressor (HPC) 
air ducts and mating hardware and replacement with newly designed air 
ducts and reworked mating hardware. This amendment also requires the 
repetitive inspection of certain reworked mating hardware. This 
amendment is prompted by reports of an uncontained low pressure turbine 
(LPT) disk failure that resulted from an air duct failure that caused a 
fan mid shaft (FMS) separation. The actions specified by this AD are 
intended to prevent HPC air duct failures that could result in FMS 
failures, that in turn could result in rejected takeoffs or uncontained 
LPT events, and to prevent HPC rear shaft failures that could result in 
uncontained engine failures.

DATES: Effective date July 26, 2001. The incorporation by reference of 
certain publications listed in the regulations is approved by the 
Director of the Federal Register as of July 26, 2001.

ADDRESSES: The service information referenced in this AD may be 
obtained from General Electric Company via Lockheed Martin Technology 
Services, 10525 Chester Road, Suite C, Cincinnati, Ohio 45215, 
telephone: (513) 672-8400; fax: (513) 672-8422. You may examine the AD 
docket (including any comments and service information) at the FAA, New 
England Region, Office of the Regional Counsel, 12 New England 
Executive Park, Burlington, MA between 8:00 a.m. and 4:30 p.m., Monday 
through Friday, except Federal holidays. You may also examine the 
service information at the Office of the Federal Register, 800 North 
Capitol Street, NW, suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Karen Curtis, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington MA 01803-5299; telephone: (781) 
238-7192; 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 GE CF6-50 turbofan engines was published in the Federal 
Register on November 24, 2000 (65 FR 70533). That action proposed to 
require removal of old high pressure compressor (HPC) air ducts and 
mating hardware and replacement with newly designed air ducts and 
reworked mating hardware in accordance with GE Aircraft Engines (GEAE) 
Service Bulletin (SB) CF6-50 72-1200, dated May 8, 2000; GEAE Alert 
Service Bulletin (ASB) CF6-50 72-A1200, Revision 1, dated July 20, 
2000; or GEAE ASB CF6-50 72-A1200, Revision 2, dated November 2, 
2000.Those bulletins describe procedures for removal of the HPC air 
duct assembly, part numbers (P/N's): 9128M36G03 / G04 / G05 / G06 / G08 
/ G20 / G21 or 1644M16G03 and mating hardware (rear shaft or stage 11-
14 spool shaft) and replacement with the new design air duct and 
reworked mating hardware.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Typographical Error

    One commenter notes that there is a typographical error in 
paragraph (a) of the proposed rule. The error is in the 
P/N for the air duct assembly. There is no P/N 99128M36G03. The FAA 
agrees, and has changed the P/N reference from 99128M36G03 to 
9128M36G03.

Cost of 3-9 Spool Inspections

    One commenter requests that the cost of the stage 3-9 spool 
inspections required by other AD's be included in the cost analysis for 
this rule as well. The FAA does not agree. The costs of the stage 3-9 
spool inspections required by other AD's were accounted for in the rule 
making process for those rules. This AD does not require additional 
stage 3-9 spool inspections.

Shop Visit Definition

    Two commenters request that the definition of shop visit for this 
rule be modified or clarified because they believe that the shop visit 
definition in the proposed rule will force

[[Page 33167]]

incorporation of newly designed air ducts and modification of the 
mating hardware sooner than intended. The FAA agrees. The definition in 
the proposed rule would have required incorporation of the redesigned 
air duct at any time the HPC stage 2 disk flange was disassembled or 
the HPC stage 1 disk was removed, for any reason. As the commenters 
note, this occurs during routine maintenance and tying the replacement 
of the HPC air duct to that triggering event would have an unintended 
acceleration of the HPC air duct replacement program. Therefore, the 
FAA has changed the definition of HPC rotor exposure. The requirements 
of this AD are triggered on removal of the stage 3-9 spool from the HPC 
rotor structure, regardless of whether any blades, locking lugs, bolts 
or balance weights remain assembled to the spool. This change will 
achieve the intended rate of compliance for the redesigned air duct 
incorporation while maintaining an acceptable level of safety.

Revision of Economic Impact

    Two commenters believe that the cost analysis of the AD should be 
revised to reflect a higher cost due to additional maintenance or 
inspections that will be needed once the HPC is disassembled to piece-
part level for the rework and installation of the new air duct. The FAA 
does not agree. The costs cited in the proposal reflect the costs for 
complying with this AD. Other potential costs that may be incurred for 
other reasons (i.e. normal maintenance or other AD required 
inspections) are not included in the cost analysis for the actions 
required by this AD.

Inspection of Certain Reworked Rear Shafts

    In addition, a comment was received to Docket No. 90-ANE-25-AD in 
response to a Notice of Proposed Rulemaking (NPRM) published on October 
12, 2000 (65 FR 60597) that proposed to revise AD 91-10-03 R1. That 
proposed revision was to add reworked rear shaft part numbers to the 
list of affected parts in AD 91-10-03 R1 to ensure that the necessary 
inspections were continued following rework and reidentification of the 
parts. The rework is required in order to use these rear shafts with 
the redesigned air duct, and does not address the bolt hole condition 
that prompted the inspection requirements of 91-10-03 R1. The commenter 
believed that the new effective date of the proposed revision to AD 91-
10-03 R1 could be misconstrued and result in parts continuing in 
service without the required inspections for longer than intended by AD 
91-10-03 R1.
    The FAA agrees that the new effectivity date of the proposed 
revision to AD 91-10-03 R1 could reduce the intended level of safety. 
Therefore, the NPRM Docket No. 90-ANE-25-AD is being withdrawn, and the 
requirement to inspect the reworked shafts that was proposed by that 
proposed rule has instead been incorporated into this final rule. 
Incorporation of the air duct required by this rule also requires that 
the existing rear shafts be reworked and reidentified in order to be 
used with the new air duct design. The rework procedure requires that 
the rear shaft be inspected at the time of the rework, regardless of 
any prior inspection history. Part of that inspection includes the same 
fluorescent penetrant inspection required by AD 91-10-03 R1. If the 
part has not already received an initial inspection in accordance with 
AD 91-10-03 R1, it will receive the necessary inspection as part of the 
rework procedure. Therefore, the repetitive inspection interval of 
6,000 CSLI will be added to this AD for reworked and reidentified rear 
shafts. The additional cost for this inspection has been added to the 
cost analysis for this AD.
    Finally, the applicability for this AD now also reflects the 
reidentified rear shafts. The total number of engines affected by this 
AD, however, remains the same because the incorporation of the new air 
duct also requires modification of the rear shaft.

Service Bulletin update

    The FAA has added to paragraph (a) a reference to GE Aircraft 
Engines Alert Service Bulletin CF6-50 72-A1200, Revision 3, dated May 
30, 2001, as an option by which to perform the required air duct 
replacement and rework of the mating hardware.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes described 
previously. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Economic Impact

    There are about 1,730 engines of the affected design in the 
worldwide fleet. The FAA estimates that 469 engines installed on 
aircraft of U.S. registry would be affected by this AD, that it would 
take about 70 work hours per engine to disassemble and reassemble the 
HPC module, that it would take 19 hours to rework the mating hardware, 
that the repetitive inspection of each reworked rear shaft would take 
two hours, and that the average labor rate is $60 per work hour. Each 
new air duct assembly will cost $32,985. Based on these figures, the 
total AD cost impact on U.S. operators is estimated to be $18,030,705.

Regulatory Impact

    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, 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 a new airworthiness directive 
to read as follows:

2001-12-20  General Electric Company (GE) CF6-50 turbofan engines: 
Amendment 39-12276. Docket 2000-NE-30-AD.

[[Page 33168]]

Applicability

    This airworthiness directive (AD) is applicable to General 
Electric Company (GE) CF6-50 turbofan engines with high pressure 
compressor (HPC) rotor air duct assemblies, part numbers (P/N's): 
9128M36G03 / G04 / G05 / G06 / G08 / G20 / G21, or 1644M16G03 
installed. This AD is also applicable to CF6-50 turbofan engines 
with HPC rear shaft P/N's: 1999M25P01 / P02 / P03 / P04 / P05 / P06 
/ or P07 installed. These engines are installed on but not limited 
to Boeing 747, Airbus A300, and McDonnell Douglas DC10 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 (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

    Compliance with the requirements of this AD is required as 
indicated, unless already done.
    To prevent HPC air duct failures that could result in fan mid 
shaft (FMS) failures and uncontained low pressure turbine (LPT) 
events, and to prevent HPC rear shaft failures that could result in 
uncontained engine failures, do the following:
    (a) At next HPC rotor exposure, remove the HPC air duct assembly 
P/N's: 9128M36G03 / G04 / G05 / G06 / G08 / G20 / G21 or 1644M16G03 
and mating hardware (rear shaft or stage 11-14 spool shaft) and 
replace with the new design air duct and reworked mating hardware in 
accordance with the accomplishment instructions of GE Aircraft 
Engines (GEAE) Service Bulletin (SB) CF6-50 72-1200, dated May 8, 
2000; GEAE Alert Service Bulletin (ASB) CF6-50 72-A1200, Revision 1, 
dated July 20, 2000; GEAE ASB CF6-50 72-A1200, Revision 2, dated 
November 2, 2000; or GEAE ASB CF6-50 72-A1200, Revision 3, dated May 
30, 2001.
    (b) Inspect rear shaft P/N's: 1999M25P01 / P02 / P03 / P04 / P05 
/ P06 / or P07 in accordance with the Accomplishment Instructions of 
GEAE ASB CF6-50 72-A0958, Revision 3, dated May 25, 2001, at 
intervals not to exceed 6,000 cycles since last inspection.
    (c) For the purposes of this AD, HPC rotor exposure is defined 
as disassembly and removal of the stage 3-9 spool from the HPC rotor 
structure, regardless of whether any blades, locking lugs, bolts or 
balance weights remain assembled to the spool.

Alternative Methods of Compliance

    (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 (ECO). 
Operators shall submit their request through an appropriate Federal 
Aviation Administration (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.

Documents That Have Been Incorporated by Reference

    (e) The actions shall be done in accordance with the following 
GE Aircraft Engines service bulletin (SB) and alert service 
bulletins (ASB's):

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           Document No.                     Pages                Revision                      Date
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SB CF6-50 72-1200.................  All..................  Original............  May 8, 2000.
    Total pages: 17
ASB CF6-50 72-A1200...............  All..................  1...................  July 20, 2000.
    Total pages: 18
ASB CF6-50 72-A1200...............  All..................  2...................  November 2, 2000.
    Total pages: 19
ASB CF6-50 72-A1200...............  All..................  3...................  May 30, 2001.
    Total pages: 21
ASB CF6-50 72-A0958...............  All..................  3...................  May 25, 2001.
    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 Company via 
Lockheed Martin Technology Services, 10525 Chester Road, Suite C, 
Cincinnati, Ohio 45215, telephone: (513) 672-8400; 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.

Effective Date

    (f) This amendment becomes effective on July 26, 2001.

    Issued in Burlington, Massachusetts, on June 13, 2001.
Wayne E. Gaulzetti,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 01-15446 Filed 6-20-01; 8:45 am]
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