[Federal Register Volume 77, Number 20 (Tuesday, January 31, 2012)]
[Rules and Regulations]
[Pages 4650-4653]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-1953]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2010-0068; Directorate Identifier 2010-NE-05-AD; 
Amendment 39-16930; AD 2012-02-07]
RIN 2120-AA64


Airworthiness Directives; General Electric Company Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are superseding two existing airworthiness directives (ADs) 
for General Electric Company (GE) CF6-45 and CF6-50 series turbofan 
engines with certain low-pressure turbine (LPT) rotor stage 3 disks 
installed. The existing ADs currently require inspections of high-
pressure turbine (HPT) and LPT rotors, engine checks, and vibration 
surveys. This new AD retains the requirements of the two ADs being 
superseded, adds an optional LPT rotor stage 3 disk removal after a 
failed HPT blade borescope inspection (BSI) or a failed engine core 
vibration survey, establishes a new lower life limit for the affected 
LPT rotor stage 3 disks, and requires removing these disks from service 
at times determined by a drawdown plan. This AD was prompted by the 
determination that a new lower life limit for the LPT rotor stage 3 
disks is necessary. We are issuing this AD to prevent critical life-
limited rotating engine part failure, which could result in an 
uncontained engine failure and damage to the airplane.

DATES: This AD is effective March 6, 2012.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of February 22, 
2011 (76 FR 6323, February 4, 2011).

ADDRESSES: For service information identified in this AD, contact 
General Electric Company, GE-Aviation, Room 285, 1 Neumann Way, 
Cincinnati, OH 45215, phone: (513) 552-3272; email: [email protected]. 
You may review copies of the referenced service information at the FAA, 
Engine & Propeller Directorate, 12 New England Executive Park, 
Burlington, MA. For information on the availability of this material at 
the FAA, call (781) 238-7125.

Examining the AD Docket

    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; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to supersede AD 2011-02-07, Amendment 39-16580 (76 FR 6323, 
February 4, 2011) and AD 2011-18-01, Amendment 39-16783 (76 FR 52213, 
August 22, 2011). Those ADs apply to the specified products. The NPRM 
published in the Federal Register on October 19, 2011 (76 FR 64844). 
That NPRM proposed to retain the requirements of AD 2011-02-07 and AD 
2011-18-01, except that reporting to the FAA would no longer be 
required and there would be an optional LPT rotor stage 3 disk removal 
after a failed HPT blade BSI or a failed engine core vibration survey. 
That NPRM also proposed to establish a new lower life limit for the LPT 
rotor stage 3 disk part numbers listed in Table 1 of the proposed AD, 
and proposed to require removing these disks from service at times 
determined by a drawdown plan.

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

    One commenter, The Boeing Company, supports the NPRM (76 FR 64844, 
October 19, 2011) as written.

[[Page 4651]]

Request To Allow Credit for Vibration Surveys Performed in a Test Cell

    One commenter, MTU Maintenance Hannover GmbH, requested that we add 
a paragraph that allows credit for performing vibration surveys in a 
test cell, as meeting the AD vibration survey requirements.
    We agree. We added paragraph (k)(8) to the AD, which states 
``Vibration surveys carried out in an engine test cell as part of an 
engine manual performance run fulfill the vibration survey requirements 
of paragraphs (k)(2) through (k)(3) of this AD.''

Request To Add a Requirement for Raw Exhaust Gas Temperature (EGT) 
Trend Data Point Exceedance

    One commenter, Evergreen International Airlines, requested that we 
add a requirement that two consecutive raw EGT trend data point 
exceedances must be confirmed by a corresponding shift of other engine 
parameters to trigger the HPT blade BSI.
    We partially agree. We agree that EGT system error should not force 
a BSI of turbine blades. But we disagree with troubleshooting the EGT 
raw data points once the EGT system error was ruled out. We added 
paragraph (o)(4) to the AD to state that, for the purposes of this AD, 
a raw EGT trend data point above the smoothed average is a confirmed 
temperature reading over the rolling average of EGT readings that is 
not a result of EGT system error. We also rearranged the wording in 
paragraph (iv) in Table 2 of the AD for clarification.

Correction to Engine Model CF6-50-E2D

    Since we issued the NPRM (76 FR 67844, October 19, 2011), we 
discovered that, in applicability paragraph (c), engine model CF6-50-
E2D was incorrect. We corrected it to read CF6-50E2B in the 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 have determined that 
these minor changes:
     Are consistent with the intent that was proposed in the 
NPRM (76 FR 64844, October 19, 2011) for correcting the unsafe 
condition; and
     Do not add any additional burden upon the public than was 
already proposed in the NPRM.
    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 CF6-45 and CF6-50 series 
turbofan engines installed on airplanes of U.S. registry. We also 
estimate that it will take about 8 work-hours to perform the HPT blade 
inspection, 6 work-hours to perform a vibration survey, 4 work-hours to 
perform an ultrasonic inspection, 2 work-hours to perform an EGT 
resistance check, 1 work-hour to perform an EGT thermocouple 
inspection, and 7 work-hours to clean and perform an fluorescent-
penetrant inspection of the LPT rotor stage 3 disk for each engine. The 
average labor rate is $85 per work-hour. The cost estimate for the work 
just described was covered in the two ADs we are superseding. For this 
AD, we estimate that a replacement LPT rotor stage 3 disk prorated part 
cost is $75,000. Based on these figures, we estimate the total cost of 
this AD to U.S. operators to be $29,025,000.

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),
    (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.

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]

    The FAA amends Sec.  39.13 by removing airworthiness directive (AD) 
2011-02-07, Amendment 39-16580 (76 FR 6323, February 4, 2011) and AD 
2011-18-01, Amendment 39-16783 (76 FR 52213, August 22, 2011), and 
adding the following new AD:

2012-02-07 General Electric Company: Amendment 39-16930; Docket No. 
FAA-2010-0068; Directorate Identifier 2010-NE-05-AD.

(a) Effective Date

    This airworthiness directive (AD) is effective March 6, 2012.

(b) Affected ADs

    This AD supersedes AD 2011-02-07, Amendment 39-16580 (76 FR 
6323, February 4, 2011) and AD 2011-18-01, Amendment 39-16783 (76 FR 
52213, August 22, 2011).

(c) Applicability

    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, CF6-50E2, and CF6-50E2B turbofan 
engines, including engines marked on the engine data plate as CF6-
50C2-F and CF6-50C2-R, with any of the low-pressure turbine (LPT) 
rotor stage 3 disk part numbers listed in Table 1 of this AD 
installed.

[[Page 4652]]



                             Table 1--Applicable LPT Rotor Stage 3 Disk Part Numbers
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9061M23P06             9061M23P07             9061M23P08             9061M23P09             9224M75P01
9061M23P10             1473M90P01             1473M90P02             1473M90P03             1473M90P04
9061M23P12             9061M23P14             9061M23P15             9061M23P16             1479M75P01
1479M75P02             1479M75P03             1479M75P04             1479M75P05             1479M75P06
1479M75P07             1479M75P08             1479M75P09             1479M75P11             1479M75P13
1479M75P14             N/A                    N/A                    N/A                    N/A
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(d) Unsafe Condition

    This AD was prompted by the determination that a new lower life 
limit for the LPT rotor stage 3 disks listed in Table 1 of this AD 
is necessary. We are issuing this AD to prevent critical life-
limited rotating engine part failure, which could result in an 
uncontained engine failure and damage to the airplane.

(e) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(f) Borescope Inspections (BSI) of High-Pressure Turbine (HPT) Rotor 
Stage 1 and Stage 2 Blades

    For the BSIs required by paragraphs (f)(1), (f)(2), and (f)(3) 
of this AD, inspect the blades from the forward and aft directions. 
Inspect all areas of the blade airfoil. Your inspection must include 
blade leading and trailing edges and their convex and concave 
airfoil surfaces. Inspect for signs of impact, cracking, burning, 
damage, or distress.
    (1) Perform an initial BSI of the HPT rotor stage 1 and stage 2 
blades within 10 cycles after the effective date of this AD.
    (2) Thereafter, repeat the BSI of the HPT rotor stage 1 and 
stage 2 blades within every 75 cycles since last inspection (CSLI).
    (3) Borescope-inspect the HPT rotor stage 1 and stage 2 blades 
within the cycle limits after the engine has experienced any of the 
events specified in Table 2 of this AD.
    (4) Remove any engine from service before further flight if the 
engine fails any of the BSIs required by this AD.

                                        Table 2--Conditional BSI Criteria
----------------------------------------------------------------------------------------------------------------
        If the engine has experienced:                               Then borescope-inspect:
----------------------------------------------------------------------------------------------------------------
(i) An exhaust gas temperature (EGT) above      Within 10 cycles.
 redline..
(ii) A shift in the smoothed EGT trending data  Within 10 cycles.
 that exceeds 18 [deg]F (10 [deg]C), but is
 less than or equal to 36 [deg]F (20 [deg]C).
(iii) A shift in the smoothed EGT trending      Before further flight.
 data that exceeds 36 [deg]F (20 [deg]C).
(iv) Two consecutive raw EGT trend data points  Within 10 cycles.
 that exceed 18 [deg]F (10 [deg]C), but is
 less than or equal to 36 [deg]F (20 [deg]C),
 above the smoothed average.
(v) Two consecutive raw EGT trend data points   Before further flight.
 that exceed 36 [deg]F (20 [deg]C) above the
 smoothed average.
----------------------------------------------------------------------------------------------------------------

(g) Actions Required for Engines With Damaged HPT Rotor Blades

    For those engines that fail any BSI requirements of this AD, 
before returning the engine to service:
    (1) Remove the LPT rotor stage 3 disk from service; or
    (2) Perform a fluorescent-penetrant inspection (FPI) of the 
inner diameter surface forward cone body (forward spacer arm) of the 
LPT rotor stage 3 disk as specified in paragraphs (l)(1)(i) through 
(l)(1)(iii) of this AD.

(h) EGT Thermocouple Probe Inspections

    (1) Inspect the EGT thermocouple probe for damage within 50 
cycles after the effective date of this AD or before accumulating 
750 CSLI, whichever occurs later.
    (2) Thereafter, re-inspect the EGT thermocouple probe for damage 
within every 750 CSLI.
    (3) If any EGT thermocouple probe shows wear through the 
thermocouple guide sleeve, remove and replace the EGT thermocouple 
probe before further flight, and ensure the turbine mid-frame liner 
does not contact the EGT thermocouple probe.

(i) EGT System Resistance Check Inspections

    (1) Perform an EGT system resistance check within 50 cycles from 
the effective date of this AD or before accumulating 750 cycles 
since the last resistance check on the EGT system, whichever occurs 
later.
    (2) Thereafter, repeat the EGT system resistance check within 
every 750 cycles since the last resistance check.
    (3) Remove and replace, or repair any EGT system component that 
fails the resistance system check before further flight.

(j) Ultrasonic Inspection (UI) of the LPT Rotor Stage 3 Disk Forward 
Spacer Arm

    Within 75 cycles after the effective date of this AD, perform a 
UI of the forward spacer arm of the LPT rotor stage 3 disk. Use 
Appendix A of GE Service Bulletin (SB) No. CF6-50 S/B 72-1312, 
Revision 1, dated October 18, 2010, paragraph 4. except for 
paragraph 4.(12), to do the UI.

(k) Engine Core Vibration Survey

    (1) Within 75 cycles after the effective date of this AD, 
perform an initial engine core vibration survey.
    (2) Use about a one-minute acceleration and a one-minute 
deceleration of the engine between ground idle and 84% N2 (about 
8,250 rpm) to perform the engine core vibration survey.
    (3) Use a spectral/trim balance analyzer or equivalent to 
measure the N2 rotor vibration.
    (4) If the vibration level is above 5 mils Double Amplitude 
then, before further flight, remove the engine from service.
    (5) For those engines that fail any engine core vibration survey 
requirements of this AD, then before returning the engine to 
service:
    (i) Remove the LPT rotor stage 3 disk from service; or
    (ii) Perform an FPI of the inner diameter surface forward spacer 
arm of the LPT rotor stage 3 disk as specified in paragraphs 
(l)(1)(i) through (l)(1)(iii) of this AD.
    (6) Thereafter, within every 350 cycles since the last engine 
core vibration survey, perform the engine core vibration survey as 
required in paragraphs (k)(1) through (k)(5) of this AD.
    (7) If the engine has experienced any vibration reported by 
maintenance or flight crew that is suspected to be caused by the 
engine core (N2), perform the engine core vibration survey as 
required in paragraphs (k)(1) through (k)(5) of this AD within 10 
cycles after the report.
    (8) Vibration surveys carried out in an engine test cell as part 
of an engine manual performance run fulfill the vibration survey 
requirements of paragraphs (k)(2) through (k)(3) of this AD.

(l) Initial and Repetitive FPI of LPT Rotor Stage 3 Disks

    (1) At the next shop visit after the effective date of this AD:
    (i) Clean the LPT rotor stage 3 disk forward spacer arm, 
including the use of a wet-abrasive blast, to eliminate residual or 
background fluorescence.
    (ii) Perform an FPI of the LPT rotor stage 3 disk forward spacer 
arm for cracks and for a band of fluorescence. Include all areas of 
the disk forward spacer arm and the inner diameter surface forward 
spacer arm of the LPT rotor stage 3 disk.

[[Page 4653]]

    (iii) Remove the disk from service before further flight if a 
crack or a band of fluorescence is present.
    (2) Thereafter, clean and perform an FPI of the LPT rotor stage 
3 disk forward spacer arm, as specified in paragraphs (l)(1)(i) 
through (l)(1)(iii) 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.

(m) Removal of LPT Rotor Stage 3 Disks

    Remove LPT rotor stage 3 disks listed in Table 1 from service as 
follows:
    (1) For disks that have fewer than 3,200 flight cycles since new 
(CSN) on the effective date of this AD, remove the disk from service 
before exceeding 6,200 CSN.
    (2) For disks that have 3,200 CSN or more on the effective date 
of this AD, do the following:
    (i) If the engine has a shop visit before the disk exceeds 6,200 
CSN, remove the disk from service before exceeding 6,200 CSN.
    (ii) If the engine does not have a shop visit before the disk 
exceeds 6,200 CSN, remove the disk from service at the next shop 
visit after 6,200 CSN, not to exceed 3,000 cycles from the effective 
date of this AD.

(n) Installation Prohibition

    (1) After the effective date of this AD, do not install or 
reinstall in any engine any LPT rotor stage 3 disk that exceeds the 
new life limit of 6,200 CSN.
    (2) Remove from service any LPT rotor stage 3 disk that is 
installed or re-installed after the effective date of this AD, 
before the disk exceeds the new life limit of 6,200 CSN.

(o) Definitions

    (1) For the purposes of this AD, an EGT above redline is a 
confirmed over-temperature indication that is not a result of EGT 
system error.
    (2) For the purposes of this AD, a shift in the smoothed EGT 
trending data is a shift in a rolling average of EGT readings that 
can be confirmed by a corresponding shift in the trending of fuel 
flow or fan speed/core speed (N1/N2) relationship. You can find 
further guidance about evaluating EGT trend data in GE Company 
Service Rep Tip 373 ''Guidelines For Parameter Trend Monitoring.''
    (3) For the purposes of this AD, an engine shop visit is the 
induction of an engine into the shop after the effective date of 
this AD, where the separation of a major engine flange occurs; 
except the following maintenance actions, or any combination, are 
not considered engine shop visits:
    (i) Induction of an engine into a shop solely for removal of the 
compressor top or bottom case for airfoil maintenance or variable 
stator vane bushing replacement.
    (ii) Induction of an engine into a shop solely for removal or 
replacement of the stage 1 fan disk.
    (iii) Induction of an engine into a shop solely for replacement 
of the turbine rear frame.
    (iv) Induction of an engine into a shop solely for replacement 
of the accessory gearbox or transfer gearbox, or both.
    (v) Induction of an engine into a shop solely for replacement of 
the fan forward case.
    (4) For the purposes of this AD, a raw EGT trend data point 
above the smoothed average is a confirmed temperature reading over 
the rolling average of EGT readings that is not a result of EGT 
system error.

(p) Previous Credit

    (1) A BSI performed before the effective date of this AD using 
AD 2010-06-15, Amendment 39-16240 (75 FR 12661, March 17, 2010) or 
AD 2010-12-10, Amendment 39-16331 (75 FR 32649, June 9, 2010) or AD 
2011-02-07, Amendment 39-16580 (76 FR 6323, February 4, 2011) within 
the last 75 cycles, satisfies the initial BSI requirement in 
paragraph (f)(1) of this AD.
    (2) A UI performed before the effective date of this AD using AD 
2011-02-07, Amendment 39-16580 (76 FR 6323, February 4, 2011) or GE 
SB No. CF6-50 S/B 72-1312, dated August 9, 2010 or GE SB No. CF6-50 
S/B 72-1312 Revision 1, dated October 18, 2010, satisfies the 
inspection requirement in paragraph (j) of this AD.
    (3) An engine core vibration survey performed before the 
effective date of this AD using AD 2011-02-07, Amendment 39-16580 
(76 FR 6323, February 4, 2011) or GE SB No. CF6-50 S/B 72-1313, 
dated August 9, 2010 or GE SB No. CF6-50 S/B 72-1313 Revision 1, 
dated October 18, 2010, within the last 350 cycles, satisfies the 
initial survey requirement in paragraphs (k)(1) through (k)(5) of 
this AD.
    (4) An FPI of the LPT rotor stage 3 disk forward spacer arm 
performed before the effective date of this AD using AD 2011-18-01, 
Amendment 39-16783 (75 FR 52213, August 22, 2011), within the last 
1,000 flight cycles of the LPT rotor stage 3 disk, satisfies the 
initial inspection requirements in paragraphs (l)(1)(i) through 
(l)(1)(iii) of this AD.

(q) Alternative Methods of Compliance (AMOCs)

    (1) AMOCs previously approved for AD 2010-06-15, Amendment 39-
16240 (75 FR 12661, March 17, 2010) are not approved for this AD. 
However, AMOCs previously approved for AD 2010-12-10, Amendment 39-
16331 (75 FR 32649, June 9, 2010), AD 2011-02-07, Amendment 39-16580 
(76 FR 6323, February 4, 2011), or AD 2011-18-01, Amendment 39-16783 
(76 FR 52213, August 22, 2011) are approved for this AD.
    (2) The Manager, Engine Certification Office, may approve 
alternative methods of compliance for this AD. Use the procedures 
found in 14 CFR 39.19 to make your request.

(r) Related Information

    (1) 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; email: 
[email protected].
    (2) For service information identified in this AD, contact 
General Electric Company, GE-Aviation, Room 285, 1 Neumann Way, 
Cincinnati, OH 45215, phone: (513) 552-3272; email: [email protected]. 
You may review copies of the referenced service information at the 
FAA, Engine & Propeller Directorate, 12 New England Executive Park, 
Burlington, MA. For information on the availability of this material 
at the FAA, call (781) 238-7125.

(s) Material Incorporated by Reference

    (1) You must use the following service information to do the UIs 
required by this AD, unless the AD specifies otherwise. The Director 
of the Federal Register approved the incorporation by reference 
(IBR) under 5 U.S.C. 552(a) and 1 CFR part 51 of the following 
service information on July 22, 2011: General Electric Company 
Service Bulletin No. CF6-50 S/B 72-1312 Revision 1, dated October 
18, 2010.
    (2) For service information identified in this AD, contact 
General Electric Company, GE-Aviation, Room 285, 1 Neumann Way, 
Cincinnati, OH 45215, phone: (513) 552-3272; email: [email protected].
    (3) You may review copies of the service information at the FAA, 
Engine & Propeller Directorate, 12 New England Executive Park, 
Burlington, MA. For information on the availability of this material 
at the FAA, call (781) 238-7125.
    (4) You may also review copies of the service information that 
is incorporated by reference 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/cfr/ibr_locations.html.

    Issued in Burlington, Massachusetts, on January 20, 2012.
Peter A. White,
Manager, Engine & Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-1953 Filed 1-30-12; 8:45 am]
BILLING CODE 4910-13-P