Airworthiness Directives; General Electric Company (GE) CF6-45 Series and CF6-50 Series Turbofan Engines

[Federal Register Volume 76, Number 162 (Monday, August 22, 2011)]
[Rules and Regulations]
[Pages 52213-52215]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-21312]



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Federal Register / Vol. 76, No. 162 / Monday, August 22, 2011 / Rules 
and Regulations

[[Page 52213]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2010-0998; Directorate Identifier 2010-NE-29-AD; 
Amendment 39-16783; AD 2011-18-01]
RIN 2120-AA64


Airworthiness Directives; General Electric Company (GE) CF6-45 
Series and CF6-50 Series Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: We are adopting a new airworthiness directive (AD) for the 
products listed above. This AD requires performing a fluorescent 
penetrant inspection (FPI) of the low-pressure turbine (LPT) rotor 
stage 3 disk at every shop visit at which the LPT module is separated 
from the engine. This AD was prompted by seven reports of uncontained 
failures of LPT rotor stage 3 disks and eight reports of cracked LPT 
rotor stage 3 disks found during shop visit inspections. We are issuing 
this AD to prevent LPT rotor separation, which could result in an 
uncontained engine failure and damage to the airplane.

DATES: This AD is effective September 26, 2011.

ADDRESSES: You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this AD, the regulatory evaluation, 
any comments received, and other information. The address for the 
Docket Office (phone: 800-647-5527) is Document Management Facility, 
U.S. Department of Transportation, Docket Operations, M-30, West 
Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., 
Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Tomasz Rakowski, Aerospace Engineer, 
Engine Certification Office, FAA, Engine & Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803; phone: (781) 238-
7735; fax: (781) 238-7199; e-mail: [email protected].

SUPPLEMENTARY INFORMATION:

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to include an airworthiness directive (AD) that would apply to 
the specified products. That NPRM published in the Federal Register on 
October 20, 2010, (75 FR 64681). That NPRM proposed to require 
performing a fluorescent penetrant inspection at every shop visit when 
the LPT module assembly is separated from the engine.

Comments

    We gave the public the opportunity to participate in developing 
this AD. The following presents the comments received on the proposal 
and the FAA's response to each comment.

Support for the NPRM as Written

    Two commenters, the National Transportation Safety Board and The 
Boeing Company support the NPRM as written.

Request To Define LPT Module

    Two commenters, GE and MTU Maintenance Canada, asked us to define 
``LPT module.'' The commenters feel the term LPT module could be 
confused with the LPT rotor assembly.
    We agree. We changed paragraph (e) of the proposed AD to clarify 
that the intent of this AD is to inspect the LPT rotor stage 3 disk 
when the LPT module assembly separates from the engine for maintenance, 
and added new paragraphs (i) and (i)(1) that define the LPT module 
assembly.

Request To Require Only Conditional Inspection

    One commenter, MTU Maintenance Canada, asked us to change the 
compliance time for the inspection. MTU stated the proposed AD requires 
stage 3 disk FPI at piece-part level regardless of the part utilization 
(cycles-since-last inspection) or operational history since the last 
inspection. MTU asked us to change the inspection to the next time the 
LPT module assembly is disassembled to piece-part level for certain 
engine conditions only.
    We don't agree with the request for conditional inspections only. 
The intent of this AD is to require an FPI of the LPT rotor stage 3 
disk forward spacer arm at each shop visit where the LPT module 
assembly is separated in a cyclic manner, regardless of the reason for 
the separation. The requirements for conditional piece-part FPI are 
already mandated by AD 2011-02-07. We didn't change the AD.

Request To Add Conditional Inspection

    One commenter, Evergreen International Airlines, asked us to 
additionally require the inspection if the engine encountered excessive 
core vibration, or HPT blade separation or excessive material loss, or 
unserviceable LPT blade interlock wear, in addition to the repetitive 
inspections proposed in the NPRM.
    We don't agree. The requirements for conditional piece-part FPI are 
already mandated by AD 2011-02-07. We didn't change the AD.

Request To Change the Compliance Time for the Inspection

    One commenter, Evergreen International Airlines, asked us to 
require inspections if the LPT rotor stage 3 disk hasn't been FPI 
inspected within the last 2,000 cycles or at all. Evergreen stated the 
separation of the LPT module is required when the maintenance of 
certain HPC, combustor, and HPT assemblies and parts need to be 
performed. Engines removed for maintenance of those components would 
require LPT rotor stage 3 disk cleaning and FPI regardless of the time 
interval since the last FPI per the proposed AD, which would be an 
unnecessary burden on the operators.
    We partially agree. We agree with the request for a certain number 
of cycles since the last FPI to exclude the part from mandatory 
inspection. However, we do not find the number of 2,000 cycles since 
last inspection (CSLI) appropriate to ensure a desired level of safety. 
We find that an acceptable level of safety will be retained when the 
disk FPI inspection is skipped during the shop visit if the disk was 
inspected within the last 1,000 cycles. We changed paragraphs (f) and 
(g) to ``(f) At the next shop visit after the effective date of this 
AD, clean and fluorescent

[[Page 52214]]

penetrant inspect the LPT rotor stage 3 disk forward spacer arm, 
including the use of a wet abrasive blast to eliminate residual or 
background fluorescence before inspecting. You can find guidance on 
cleaning the disk and performing the FPI in the CF6-50 Engine Manual, 
GEK 50481 72-57-02.'' and ``(g) Thereafter, clean and inspect the LPT 
rotor stage 3 disk forward spacer arm, as specified in paragraph (f), 
at each engine shop visit that occurs after 1,000 cycles since the last 
FPI of the LPT rotor stage 3 disk forward spacer arm.'' We also added 
paragraphs (i) and (i)(2) that define an engine shop visit as follows: 
``An engine shop visit is the induction of an engine into the shop for 
maintenance involving the separation of the turbine mid-frame forward 
flange from the compressor rear frame aft flange, except that the 
separation of these engine flanges solely for the purposes of 
transportation without subsequent engine maintenance does not 
constitute an engine shop visit.''

Request To Change the Type of Inspection

    One commenter, GE, asked us to consider changing the type of 
inspection from FPI to ultrasonic inspection (USI). GE stated that they 
have developed a USI technique and tooling which allow inspecting the 
LPT rotor stage 3 disk forward spacer arm without piece part 
disassembly of the LPT. Implementing the USI will detect cracks in the 
forward spacer arm, which might propagate during operation and would be 
a suitable alternative to the piece-part disassembly, cleaning, and FPI 
of the forward spacer arm in many situations.
    We don't agree. We don't believe USI technique specified in GE SB 
CF6-50 S/B 72-1309 is a sufficient means of detecting flaws or 
microcracks on the inner surface of the LPT rotor stage 3 disk forward 
spacer arm. Paragraph E.(5) of SB CF6-50 S/B 72-1309 states ``The new 
USI probe was specifically designed to detect flaws 0.030 inch (0.76 
mm) deep or greater in the forward spacer arm of the stage 3 LPTR 
disk.'' We find that a 0.030-inch deep surface crack size is 
unacceptable in that location, as it would have already propagated in a 
high-cycle fatigue mode. The intent of this AD is to detect cracks 
before they propagate. We made no change to the proposed AD.

Request To Change the Costs of Compliance

    Two commenters, MTU Canada and FedEx, asked us to re-evaluate the 
Costs of Compliance for the actions required by the proposed AD. The 
commenters state that cleaning the stage 3 disk and performing an FPI 
are done at the piece-part level, and that the costs of disassembling 
and reassembling the LPT module assembly, and of the inspections 
required by the engine manual for reinstalling the stage 3 blades must 
be added to the cost of cleaning and inspecting the disk.
    We don't agree. Our estimated cost is the direct cost to comply 
with the AD, and doesn't include preparatory disassembly or 
reinstallation. We didn't change the AD.

Request To Change Paragraph (f) of the Proposed AD

    One commenter, GE, asked us to change paragraph (f) of the proposed 
AD to use the words ``including the use of'' in place of the word 
``using'', where cleaning the LPT rotor stage 3 disk with wet-abrasive 
blast to eliminate residual or background fluorescence is required. GE 
doesn't consider a wet-abrasive blast alone sufficient to clean the LPT 
rotor stage 3 disk to allow performance of the FPI of the inner 
diameter of the forward cone body of the LPT rotor stage 3 disk.
    We agree. We changed paragraph (f) of the proposed AD from ``Clean 
the LPT rotor stage 3 disk, using a wet abrasive blast to eliminate 
residual or background fluorescence. You can find guidance on cleaning 
the disk in the cleaning procedure of CF6-50 Engine Manual, GEK 50481 
72-57-02.'' to ``At the next engine shop visit after the effective date 
of this AD, clean and fluorescent-penetrant inspect the LPT rotor stage 
3 disk forward spacer arm, including the use of a wet-abrasive blast to 
eliminate residual or background fluorescence before inspecting. You 
can find guidance on cleaning the disk and performing the FPI in the 
CF6-50 Engine Manual, GEK 50481 72-57-02.''

Request To Include Definitions for Cleaning and FPI of the LPT Rotor 
Stage 3 Disk

    One commenter, Evergreen International Airlines, asked us to add 
definitions of ``cleaning the LPT rotor stage 3 disk'' and ``FPI of the 
LPT rotor stage 3 disk,'' with specific engine manual subtask 
references, to the proposed AD. The commenter states that the 
definitions will clarify the actions required by the proposed AD.
    We don't agree. The reference provided in the proposed AD is 
sufficient to define the required actions. We made no changes to the 
proposed AD.

Conclusion

    We reviewed the relevant data, considered the comments received, 
and determined that air safety and the public interest require adopting 
the AD with the changes described previously.
    We also determined that these changes will not increase the 
economic burden on any operator or increase the scope of the AD.

Costs of Compliance

    We estimate that this AD will affect 387 engines installed on 
airplanes of U.S. registry. We also estimate that it will take about 7 
work-hours per engine to clean and FPI the disk 387 engines. The 
average labor rate is $85 per work-hour. No parts will be required. 
Based on these figures, we estimate the total cost of the AD to U.S. 
operators to be $230,265.

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

    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),
    (3) Will not affect intrastate aviation in Alaska, and
    (4) 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.

[[Page 52215]]

List of Subjects in 14 CFR Part 39

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

Adoption of the Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA 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 (AD):

2011-18-01 General Electric Company: Amendment 39-16783; Docket No. 
FAA-2010-0998; Directorate Identifier 2010-NE-29-AD.

Effective Date

    (a) This AD is effective September 26, 2011.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to General Electric Company (GE) CF6-45A, 
CF6-45A2, CF6-50A, CF6-50C, CF6-50CA, CF6-50C1, CF6-50C2, CF6-50C2B, 
CF6-50C2D, CF6-50E, CF6-50E1, and CF6-50E2 series turbofan engines, 
including engines marked on the engine data plate as CF6-50C2-F and 
CF6-50C2-R, with a low-pressure turbine (LPT) rotor stage 3 disk 
that has a part number (P/N) listed in Table 1 of this AD installed.

                  Table 1--LPT Rotor Stage 3 Disk P/Ns
------------------------------------------------------------------------
 
------------------------------------------------------------------------
     1473M90P01         1473M90P02         1473M90P03        1473M90P04
     1479M75P01         1479M75P02         1479M75P03        1479M75P04
     1479M75P05         1479M75P06         1479M75P07        1479M75P08
     1479M75P09         1479M75P11         1479M75P13        1479M75P14
     9061M23P06         9061M23P07         9061M23P08        9061M23P09
     9061M23P10         9061M23P12         9061M23P14        9061M23P15
     9061M23P16         9224M75P01    ................  ................
------------------------------------------------------------------------

Unsafe Condition

    (d) This AD results from seven reports of uncontained failures 
of LPT rotor stage 3 disks and eight reports of cracked LPT rotor 
stage 3 disks found during shop visit inspections. We are issuing 
this AD to prevent LPT rotor separation, which could result in an 
uncontained engine failure and damage to the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed at each shop visit after the effective date of this AD, 
at which the LPT module assembly is separated from the engine.

Initial Inspection

    (f) At the next shop visit after the effective date of this AD, 
clean and fluorescent-penetrant inspect the LPT rotor stage 3 disk 
forward spacer arm, including the use of a wet-abrasive blast to 
eliminate residual or background fluorescence before inspecting. You 
can find guidance on cleaning the disk and performing the FPI in the 
CF6-50 Engine Manual, GEK 50481 72-57-02.

Repetitive Inspection

    (g) Thereafter, clean and inspect the LPT rotor stage 3 disk 
forward spacer arm, as specified in paragraph (f) of this AD, at 
each engine shop visit that occurs after 1,000 cycles since the last 
FPI of the LPT rotor stage 3 disk forward spacer arm.
    (h) If a crack or a band of fluorescence is present, remove the 
disk from service.

Definitions

    (i) For the purpose of this AD:
    (1) The LPT module assembly is defined as consisting of turbine 
mid-frame, LPT stage 1 nozzle, LPT stator cases and vanes, LPT 
rotor, and turbine rear frame.
    (2) An engine shop visit is the induction of an engine into the 
shop for maintenance involving the separation of the turbine mid-
frame forward flange from the compressor rear frame aft flange, 
except that the separation of these engine flanges solely for the 
purposes of transportation without subsequent engine maintenance 
does not constitute an engine shop visit.

Alternative Methods of Compliance

    (j) 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

    (k) For more information about this AD, contact Tomasz Rakowski, 
Aerospace Engineer, Engine Certification Office, FAA, Engine & 
Propeller Directorate, 12 New England Executive Park, Burlington, MA 
01803; phone: (781) 238-7735; fax: (781) 238-7199; e-mail: 
[email protected].

Material Incorporated by Reference

    (l) None.

    Issued in Burlington, Massachusetts on August 15, 2011.
Peter A. White,
Manager, Engine & Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 2011-21312 Filed 8-19-11; 8:45 am]
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