Airworthiness Directives; General Electric Company CF6-45A, CF6-50A, CF6-50C, and CF6-50E Series Turbofan Engines

[Federal Register Volume 70, Number 60 (Wednesday, March 30, 2005)]
[Rules and Regulations]
[Pages 16096-16098]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-6107]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2004-19463; Directorate Identifier 2004-NE-14-AD; 
Amendment 39-14029; AD 2005-07-05]
RIN 2120-AA64


Airworthiness Directives; General Electric Company CF6-45A, CF6-
50A, CF6-50C, and CF6-50E Series Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
General Electric Company (GE) CF6-45A, CF6-50A, CF6-50C, and CF6-50E 
series turbofan engines that have not incorporated GE Service Bulletin 
(SB) No. CF6-50 S/B 72-1239, Revision 1, dated September 24, 2003, or 
that have not incorporated paragraph 3.B. of GE SB No. CF6-50 S/B 72-
1239, original issue, dated May 29, 2003. This AD requires inspecting 
the stage 1 low pressure turbine (LPT) blades for damage and 
replacement of the LPT module if necessary. This AD results from a 
report of a stud that separated from a turbine mid frame (TMF) strut 
and from an updated analysis of strut stud failures. We are issuing 
this AD to prevent uncontained failure of the engine and possible 
damage to the airplane caused by failure of TMF strut studs.

DATES: This AD becomes effective May 4, 2005. The Director of the 
Federal Register approved the incorporation by reference of certain 
publications listed in the regulations as of May 4, 2005.

ADDRESSES: You can get the service information identified in this 
proposed AD 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 on the Internet at http://dms.dot.gov 
or in Room PL-401 on the plaza level of the Nassif Building, 400 
Seventh Street, SW., 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; telephone (781) 238-
7192; fax (781) 238-7199.

SUPPLEMENTARY INFORMATION: The FAA proposed to amend 14 CFR part 39 
with an airworthiness directive (AD). The proposed AD applies to GE 
CF6-45A, CF6-50A, CF6-50C, and CF6-50E series turbofan engines that 
have not incorporated GE SB No. CF6-50 S/B 72-1239, Revision 1, dated 
September 24, 2003, or that have not incorporated paragraph 3.B. of GE 
SB No. CF6-50 S/B 72-1239, original issue, dated May 29, 2003. We 
published the proposed AD in the Federal Register on October 27, 2004 
(69 FR 62623). That action proposed to require inspecting the stage 1 
LPT blades for damage and replacement of the LPT module if necessary.

Examining the AD Docket

    You may examine the docket that contains the AD, any comments 
received, and any final disposition in person at the DMS Docket Offices 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The Docket Office (telephone (800) 647-5227) is located on 
the plaza level of the Department of Transportation Nassif Building at 
the street address stated in ADDRESSES. Comments will be available in 
the AD docket shortly after the DMS receives them.

Comments

    We provided the public the opportunity to participate in the 
development of this AD. We have considered the comments received.

Request To Clarify if Extension Limits Are Still Allowed

    One commenter requests that we clarify if the extension limits in 
aircraft maintenance manual (AMM) 72-00-00, are still allowed if out-
of-limit LPT blade damage is found during the required borescope 
inspection. The commenter provided no justification for this request.
    We do not feel we need to clarify allowing extension limits if the 
operator finds damage during the required borescope inspection. 
Paragraphs (g) and (i) of the proposed AD require replacing any LPT 
module that exceeds the AMM limits for the stage 1 LPT blade damage.

Requests for Credit for Inspections Already Performed

    One commenter requests that we give operators credit for 
inspections already performed using GE Alert Service Bulletin (ASB) No. 
72-A1251, dated September 24, 2003, before the effective date of the 
AD. Another commenter requests that we give operators credit for 
inspections already performed using an approved maintenance program. 
The commenters believe that based on the proposed AD wording, an 
operator would have to complete the initial inspection within 150 
cycles-in-service after the effective date of the AD, regardless of any 
prior inspections done.
    We agree that we should allow credit for inspection programs begun 
before the effective date of the AD. Because paragraph (e) of the 
proposed AD states that you are responsible for having this AD 
performed within the compliance times specified unless the actions have 
already been done, we feel that this statement provides credit for 
inspections already done. However, for clarity, we have added a 
paragraph (paragraph (j)) to the AD compliance that gives credit for 
initial and repetitive inspections done using GE ASB No. 72-A1251 or 
the applicable AMM.

Inspection AD Not Necessary

    One commenter states that this inspection AD is not necessary. The 
commenter's reason is that GE had previously released an improved strut 
stud joint configuration (reference GE SB No. 72-0897, dated 1987), and 
recommended that studs not be reused (reference engine manual change in 
1996). The commenter asks that we provide additional analysis to

[[Page 16097]]

substantiate the need for this inspection AD for engines configured 
with new, post-SB No. 72-0897 studs. The commenter sites their service 
experience, which has not shown wear or contact between the stud sleeve 
and nozzle support. The commenter states that the one documented 
failure of a first-run engine (non-reused stud) is an extremely rare 
and unique case because it occurred on a KC-10 military airplane 
application.
    We do not agree. We didn't make GE SB No. 72-0897, which introduced 
the improved configuration, mandatory. We also didn't make the 1996 
engine manual change, which specified the studs were not to be reused, 
mandatory. Also, GE has provided data that shows that the potential for 
contact, rubbing, and wear, exists by design, as a result of 
insufficient clearance between the hole in the LPT nozzle support and 
the sleeve fitted to the TMF strut stud. During engine operation, 
thermal and mechanical deflections between the nozzle support and the 
stud and sleeve assembly can result in contact between these components 
if minimum assembly clearance requirements are not met. This contact 
causes transverse loads and bending moments in the strut stud. The 
fatigue life of the stud is reduced as a result of these loads. The 
fracture surface of the stud involved in the most recent event showed 
signs of fatigue damage, characteristic of bending loads. Although the 
commenter has not yet experienced this condition, and there is only one 
known failure for the post SB No. 72-0897 configuration with a non-
reused stud, the potential exists for stud failure. This inspection AD 
is necessary to detect studs that have failed, and to prevent an 
uncontained engine failure.

Request To Clarify the Word ``Optional''

    One commenter requests that we clarify the word ``optional'' in the 
Optional Terminating Action paragraph of the proposed AD. The commenter 
states that incorporation of GE SB No. 72-1239 is terminating action 
for the repetitive inspections in the proposed AD.
    We do not agree. The proposed AD requires that operators perform 
the initial and repetitive inspections of the LPT. The proposed AD does 
not require that operators perform the reassembly described in GE SB 
No. 72-1239. However, if an operator chooses to perform GE SB No. 72-
1239, as described in paragraph (j) of the proposed AD (now paragraph 
(k) of the AD), the initial and repetitive inspections are no longer 
required. The incorporation of GE SB No. 72-1239 is described as 
optional, because an operator can choose to continue to perform 
repetitive inspections or incorporate that SB. Either action provides 
an acceptable level of safety.

Conclusion

    We have carefully reviewed the available data, including the 
comments received, and determined that air safety and the public 
interest require adopting the AD with the changes described previously. 
We have determined that these changes will neither increase the 
economic burden on any operator nor increase the scope of the AD.

Costs of Compliance

    There are about 2,079 GE CF6-45A, CF6-50A, CF6-50C, and CF6-50E 
series turbofan engines of the affected design in the worldwide fleet. 
We estimate that 790 engines installed on airplanes of U.S. registry 
will be affected by this AD. We also estimate that it will take about 
one work hour per engine to perform the actions, and that the average 
labor rate is $65 per work hour. Based on these figures, we estimate 
the total cost of the AD to perform one inspection to U.S. operators to 
be $51,350.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We have determined that this AD will not have federalism 
implications under Executive Order 13132. This AD will 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.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866;
    (2) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and
    (3) 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.
    We prepared a summary of the costs to comply with this AD and 
placed it in the AD Docket. You may get a copy of this summary at the 
address listed under ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the Federal Aviation Administration amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2005-07-05 General Electric Company: Amendment 39-14029. Docket No. 
FAA-2004-19463; Directorate Identifier 2004-NE-14-AD.

Effective Date

    (a) This airworthiness directive (AD) becomes effective May 4, 
2005.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to General Electric Company (GE) CF6-45A, 
CF6-50A, CF6-50C, and CF6-50E series turbofan engines that have not 
incorporated GE Service Bulletin (SB) No. CF6-50 S/B 72-1239, 
Revision 1, dated September 24, 2003, or that have not incorporated 
paragraph 3.B. of GE SB No. CF6-50 S/B 72-1239, original issue, 
dated May 29, 2003. These engines are installed on, but not limited 
to, Boeing DC10 and 747 series airplanes, and Airbus Industrie A300 
series airplanes.

Unsafe Condition

    (d) This AD results from a report of a stud that separated from 
a turbine mid frame (TMF) strut and from an updated analysis of 
strut stud failures. We are issuing this AD to prevent an 
uncontained failure of the engine and possible damage to the 
airplane caused by failure of TMF strut studs.

[[Page 16098]]

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified unless the 
actions have already been done.

Initial Inspection

    (f) Borescope-inspect the low pressure turbine (LPT) stage 1 
blades within 3,000 cycles-since-new (CSN), or 3,000 cycles-since-
replacement of the TMF strut studs, or 150 cycles-in-service (CIS) 
after the effective date of this AD, which ever occurs later. Use 
paragraph 3.A.(2) of the Accomplishment Instructions of GE Alert 
Service Bulletin (ASB) No. CF6-50 S/B 72-A1251, dated September 24, 
2003, to do the inspection.
    (g) Replace any LPT module that has stage 1 LPT blade damage 
exceeding aircraft maintenance manual (AMM) limits.

Repetitive Inspections

    (h) Borescope-inspect the LPT stage 1 blades within intervals of 
500 cycles-since-last-inspection or within 500 cycles-since-last 
shop visit, or within 150 CIS after the effective date of this AD, 
whichever occurs later. Use paragraph 3.A.(3) of the Accomplishment 
Instructions of GE ASB No. CF6-50 S/B 72-A1251, dated September 24, 
2003, to do the inspections.
    (i) Replace any LPT module that has stage 1 LPT blade damage 
exceeding AMM limits.

Credit for Previous Actions

    (j) We allow credit for compliance with paragraph (f) or (h) of 
this AD, for either of the following:
    (1) Initial or repetitive inspections of LPT stage 1 blades 
using GE ASB No. CF6-50 SB 72-A1251, dated September 24, 2003 within 
the compliance times of this AD; or
    (2) Initial or repetitive inspections of LPT stage 1 blades 
using the applicable AMM, within the compliance times of this AD.

Optional Terminating Action

    (k) Engines incorporating GE SB No. CF6-50 S/B 72-1239, Revision 
1, dated September 24, 2003, or incorporating paragraph 3.B. of GE 
SB No. CF6-50 S/B 72-1239, original issue, dated May 29, 2003, ends 
the repetitive inspection requirements in paragraph (h) of this AD.

Alternative Methods of Compliance

    (l) The Manager, Engine Certification Office, has the authority 
to approve alternative methods of compliance for this AD if 
requested using the procedures found in 14 CFR 39.19.

Related Information

    (m) None.

Material Incorporated by Reference

    (n) You must use General Electric Company Alert Service Bulletin 
No. CF6-50 S/B 72-A1251, dated September 24, 2003, to perform the 
inspections required by this AD. The Director of the Federal 
Register approved the incorporation by reference of this service 
bulletin in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. 
Contact General Electric Company via Lockheed Martin Technology 
Services, 10525 Chester Road, Suite C, Cincinnati, Ohio 45215, 
telephone (513) 672-8400, fax (513) 672-8422 for a copy of this 
service information. You may review copies at the Docket Management 
Facility; U.S. Department of Transportation, 400 Seventh Street, 
SW., Nassif Building, Room PL-401, Washington, DC 20590-001, on the 
internet at http://dms.dot.gov, or at the National Archives and 
Records Administration (NARA). For information on the availability 
of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

    Issued in Burlington, Massachusetts, on March 22, 2005.
Peter A. White,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 05-6107 Filed 3-29-05; 8:45 am]
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