Document ID: FAA-2010-0068-0020
Agency: faa
Document Type: Proposed Rule
Title: Airworthiness Directives: General Electric Co. Turbofan Engines
Posted Date: 2011-10-19T04:00Z

[Federal Register Volume 76, Number 202 (Wednesday, October 19, 2011)]
[Proposed Rules]
[Pages 64844-64847]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-27006]

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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]
RIN 2120-AA64

Airworthiness Directives; General Electric Company Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to supersede two existing airworthiness directives 
(ADs) that apply to 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 
surveys. Since we issued those ADs, GE has determined that the low-
cycle fatigue (LCF) lives of the LPT rotor stage 3 disks affected by 
those ADs are below the current published engine manual life limits and 
has introduced a new LPT rotor stage 3 disk part number. This proposed 
AD would establish a new lower life limit for the LPT rotor stage 3 
disks. We are proposing 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: We must receive comments on this proposed AD by December 5, 
2011.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    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; e-mail: geae.aoc@ge.com. 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 proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (phone: 800-647-5527) is in the ADDRESSES 
section. Comments will be available in the AD docket shortly after 
receipt.

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: tomasz.rakowski@faa.gov.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2010-0068; 
Directorate Identifier 2010-NE-05-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://

[[Page 64845]]

www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    On January 14, 2011, we issued AD 2011-02-07, Amendment 39-16580 
(76 FR 6323, February 4, 2011), for GE CF6-45 and CF6-50 series 
turbofan engines with certain LPT rotor stage 3 disks installed. That 
AD requires initial and repetitive HPT rotor stage 1 and stage 2 blade 
inspections for wear and damage, including excessive airfoil material 
loss, and initial and repetitive exhaust gas temperature (EGT) system 
checks (inspections). That AD also requires a one-time ultrasonic 
inspection (UI) of the LPT rotor stage 3 disk forward spacer arm, 
fluorescent penetrant inspection (FPI) of the LPT rotor stage 3 disk 
under certain conditions, and removal of cracked disks from service 
before further flight. That AD also requires initial and repetitive 
engine core vibration surveys and reporting to the FAA any crack 
findings, disks that fail the UI, and engines that fail the engine core 
vibration survey. That AD resulted from reports received of additional 
causes of HPT rotor imbalance not addressed in AD 2010-12-10, Amendment 
39-16331 (75 FR 32649, June 9, 2010), and from two additional LPT rotor 
stage 3 disk events since the original AD 2010-06-15, Amendment 39-
16240 (75 FR 12661, March 17, 2010) was issued.
    On August 15, 2011, we issued AD 2011-18-01, Amendment 39-16783 (76 
FR 52213, August 22, 2011) to require performing an FPI of the LPT 
rotor stage 3 disk forward spacer arm at every shop visit when the LPT 
module assembly is separated from the engine. That AD resulted 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 issued those ADs to prevent critical life-limited rotating 
engine part failure, which could result in an uncontained engine 
failure and damage to the airplane.

Actions Since Existing AD Was Issued

    Since we issued AD 2011-02-07, Amendment 39-16580 (76 FR 6323, 
February 4, 2011), GE has determined that the LCF lives of the LPT 
rotor stage 3 disks affected by that AD were below the current 
published manual life limits, and has introduced a new LPT rotor stage 
3 disk part number. Moreover, we no longer require the reporting of 
inspection findings to the FAA.

FAA's Determination

    We are proposing this AD because we evaluated all the relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of the same type design.

Proposed AD Requirements

    This proposed AD would retain the requirements of 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), 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 
borescope inspection or a failed engine core vibration survey. This 
proposed AD would also establish a new lower life limit for the LPT 
rotor stage 3 disk part numbers listed in Table 1 of the proposed AD, 
and would require removing these disks from service at times determined 
by a drawdown plan.

Costs of Compliance

    We estimate that this proposed AD would affect 387 CF6-45 and CF6-
50 series turbofan engines installed on airplanes of U.S. registry. We 
also estimate that it would 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 FPI 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 proposing to supersede. For this proposed 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 
proposed 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 proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD 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.
    For the reasons discussed above, I certify that the proposed 
regulation:
    (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),
    (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.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. 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:

General Electric Company: Docket No. FAA-2010-0068; Directorate 
Identifier 2010-NE-05-AD.

[[Page 64846]]

(a) Comments Due Date

    The FAA must receive comments on this AD action by December 5, 
2011.

(b) Affected ADs

    This AD supersedes AD 2011-02-07, Amendment 39-16580 and AD 
2011-18-01, Amendment 39-16783.

(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 CF6-50-E2D 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.

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

(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 of HPT Rotor Stage 1 and Stage 2 Blades

    For the borescope inspections 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 borescope inspection of the HPT rotor 
stage 1 and stage 2 blades, within 10 cycles after the effective 
date of this AD.
    (2) Thereafter, repeat the borescope inspection 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 borescope inspections required by this AD.

           Table 2--Conditional Borescope Inspection Criteria
------------------------------------------------------------------------
  If the engine has  experienced:          Then borescope-inspect:
------------------------------------------------------------------------
(i) An exhaust gas temperature      Within 10 cycles.
 (EGT) above redline.
(ii) A shift in the smoothed EGT    Within 10 cycles.
 trending data 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   Before further flight.
 trending data that exceeds 36
 [deg]F (20 [deg]C).
(iv) Two consecutive raw EGT trend  Within 10 cycles.
 data points that exceed 18 [deg]F
 (10 [deg]C) above the smoothed
 average, but is less than or
 equal to 36 [deg]F (20 [deg]C).
(v) Two consecutive raw EGT trend   Before further flight.
 data points 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 borescope inspection 
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 cone body (forward spacer arm) of the LPT rotor 
stage 3 disk. Use paragraphs E. through K. of Appendix A of GE 
Service Bulletin (SB) No. CF6-50-SB 72-1312, Revision 1, dated 
October 18, 2010, 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 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.

[[Page 64847]]

    (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.

(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 
cone body (forward spacer arm) of the LPT rotor stage 3 disk.
    (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) Introduction 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) Introduction of an engine into a shop solely for removal or 
replacement of the stage 1 fan disk.
    (iii) Introduction of an engine into a shop solely for 
replacement of the turbine rear frame.
    (iv) Introduction of an engine into a shop solely for 
replacement of the accessory gearbox or transfer gearbox, or both.
    (v) Introduction of an engine into a shop solely for replacement 
of the fan forward case.

(p) Previous Credit

    (1) A borescope inspection 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 
borescope inspection 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-SB 72-1312, dated August 9, 2010 or GE SB No. CF6-50-
SB 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-SB 72-1313, dated 
August 9, 2010 or GE SB No. CF6-50-SB 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 3, 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; e-mail: 
tomasz.rakowski@faa.gov.
    (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; e-mail: geae.aoc@ge.com. 
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.

    Issued in Burlington, Massachusetts, on October 13, 2011.
Peter A. White,
Manager, Engine & Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 2011-27006 Filed 10-18-11; 8:45 am]
BILLING CODE 4910-13-P