[Federal Register Volume 76, Number 202 (Wednesday, October 19, 2011)]
[Proposed Rules]
[Pages 64844-64847]
From the Federal Register Online via the Government Publishing 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: [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 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: [email protected].
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
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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 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
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If the engine has experienced: Then borescope-inspect:
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(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.
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(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:
[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; e-mail: [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.
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]
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