Airworthiness Directives; General Electric Company Turbofan Engines, 17679-17682 [2023-05472]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 88, Number 57 (Friday, March 24, 2023)]
[Rules and Regulations]
[Pages 17679-17682]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-05472]



========================================================================
Rules and Regulations
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains regulatory documents 
having general applicability and legal effect, most of which are keyed 
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under 50 titles pursuant to 44 U.S.C. 1510.

The Code of Federal Regulations is sold by the Superintendent of Documents. 

========================================================================


Federal Register / Vol. 88, No. 57 / Friday, March 24, 2023 / Rules 
and Regulations

[[Page 17679]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-1416; Project Identifier AD-2022-00725-E; 
Amendment 39-22358; AD 2023-04-11]
RIN 2120-AA64


Airworthiness Directives; General Electric Company Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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

SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2012-02-07 
for certain General Electric Company (GE) CF6-45 and CF6-50 series 
model turbofan engines with a specified low-pressure turbine (LPT) 
rotor stage 3 disk installed. AD 2012-02-07 required inspections of 
high-pressure turbine (HPT) and LPT rotors, engine checks, vibration 
surveys, an optional LPT rotor stage 3 disk removal after a failed HPT 
blade borescope inspection (BSI) or a failed engine core vibration 
survey, established a lower life limit for the affected LPT rotor stage 
3 disks, and required removing these disks from service at times 
determined by a drawdown plan. This AD was prompted by the occurrence 
of four events of separation of the LPT rotor assembly, which resulted 
in the LPT rotor assembly departing the rear of the engine. This AD 
requires inspections of HPT and LPT rotor stage 1 and stage 2 blades, 
vibration surveys, and use of a lower life limit for the affected LPT 
rotor stage 3 disks and, as terminating action to the inspections, 
engine checks, and vibration surveys, this AD requires removal and 
replacement of the LPT rotor stage 3 disk with a redesigned LPT rotor 
stage 3 disk. This AD also requires revising the compliance time of the 
drawdown plan for the removal and replacement of the LPT rotor stage 3 
disk and prohibits the installation or reinstallation of certain LPT 
rotor stage 3 disks. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective April 28, 2023.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov by 
searching for and locating Docket No. FAA-2022-1416; or in person at 
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. The AD docket contains this final rule, any 
comments received, and other information. The address for Docket 
Operations is 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: Sungmo Cho, Aviation Safety Engineer, 
ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone: 
(781) 238-7241; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to supersede AD 2012-02-07, Amendment 39-16930 (77 FR 4650, 
January 31, 2012), (``AD 2012-02-07''). AD 2012-02-07 applied to 
certain 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 model turbofan engines, including engines marked on the engine 
data plate as CF6-50C2-F and CF6-50C2-R, with a specified LPT rotor 
stage 3 disk, identified by part number (P/N), installed. The NPRM 
published in the Federal Register on December 08, 2022 (87 FR 75181). 
The NPRM was prompted by the occurrence of four events of separation of 
the LPT rotor assembly, occurring after the effective date of AD 2012-
02-07, which resulted in the LPT rotor assembly departing the rear of 
the engine. Following the most recent separation event, the FAA 
determined that due to the complexity of AD 2012-02-07, the limitations 
of certain operators to access required equipment and training needed 
to accomplish the inspections, and the manufacturer's redesign of the 
LPT rotor stage 3 disk, AD 2012-02-07 required supersedure. The 
redesigned LPT rotor stage 3 disk, P/N 2453M80P01, has a thicker 
forward spacer arm, which reduces stress on the forward arm area and 
increases its high cycle fatigue alternating stress capability. In the 
NPRM, the FAA proposed to continue to require inspections of HPT and 
LPT rotor stage 1 and stage 2 blades, vibration surveys, and use of a 
lower life limit for the affected LPT rotor stage 3 disks. As a 
terminating action to the inspections, engine checks, and vibration 
surveys, the FAA also proposed to require removal and replacement of 
the LPT rotor stage 3 disk with a redesigned LPT rotor stage 3 disk. In 
the NPRM, the FAA also proposed to require revision of the compliance 
time of the drawdown plan for the removal and replacement of the LPT 
rotor stage 3 disk, and to prohibit the installation or reinstallation 
of certain LPT rotor stage 3 disks.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from two commenters. Commenters included 
Air Line Pilots Association, International and The Boeing Company. All 
commenters supported the NPRM without change.

Conclusion

    The FAA reviewed the relevant data, considered the comments 
received, and determined that air safety requires adopting the AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. Except for minor editorial changes, this 
AD is adopted as proposed in the NPRM.

Costs of Compliance

    The FAA estimates that this AD affects 26 engines installed on 
airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this AD:

[[Page 17680]]



                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
HPT blade inspection, vibration         28 work-hours x $85 per               $0          $2,380         $61,880
 survey, UI, EGT resistance check, EGT   hour = $2,380.
 thermocouple inspection, cleaning and
 FPI of the LPT rotor stage 3 disk.
Remove and replace LPT rotor stage 3    620 work-hours x $85 per         276,300         329,000       8,554,000
 disk.                                   hour = $52,700.
----------------------------------------------------------------------------------------------------------------

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.
    The FAA is 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

    The FAA has 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) Will not affect intrastate aviation in Alaska, and
    (3) Will not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

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

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:
0
a. Removing Airworthiness Directive 2012-02-07, Amendment 39-16930 (77 
FR 4650, January 31, 2012); and
0
b. Adding the following new airworthiness directive:

2023-04-11 General Electric Company: Amendment 39-22358; Docket No. 
FAA-2022-1416; Project Identifier AD-2022-00725-E.

(a) Effective Date

    This airworthiness directive (AD) is effective April 28, 2023.

(b) Affected ADs

    This AD replaces AD 2012-02-07, Amendment 39-16930 (77 FR 4650, 
January 31, 2012) (AD 2012-02-07).

(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 model turbofan 
engines, including engines marked on the engine data plate as CF6-
50C2-F and CF6-50C2-R, with an installed low-pressure turbine (LPT) 
rotor stage 3 disk having a part number listed in Table 1 to 
paragraph (c) of this AD.

                                        Table 1 to Paragraph (c)--Applicable LPT Rotor Stage 3 Disk Part Numbers
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
                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) Subject

    Joint Aircraft System Component (JASC) Code 7250, Turbine 
Section.

(e) Unsafe Condition

    This AD was prompted by the occurrence of four events of 
separation of the LPT rotor assembly, occurring after the effective 
date of AD 2012-02-07, which resulted in the LPT rotor assembly 
departing the rear of the engine. The FAA is issuing this AD to 
prevent critical life-limited rotating engine part failure. The 
unsafe condition, if not addressed, could result in an uncontained 
engine failure and damage to the airplane.

(f) Compliance

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

(g) Required Actions

    (1) Borescope Inspections (BSI) of High-Pressure Turbine (HPT) 
Rotor Stage 1 and Stage 2 Blades. For the BSIs required by 
paragraphs (g)(1)(i) through (iii) of this AD, inspect the blades 
from the forward and aft directions. Inspect all areas of the blade 
airfoil. The inspection must include blade leading and trailing 
edges and their convex and concave airfoil surfaces. Inspect for 
signs of impact, cracking, burning, damage, and distress.
    (i) Within 75 cycles since last inspection (CSLI) or before 
further flight, whichever occurs later, perform an initial BSI of 
the HPT rotor stage 1 and stage 2 blades.
    (ii) Thereafter, within every 75 CSLI, repeat the BSI of the HPT 
rotor stage 1 and stage 2 blades.
    (iii) Within the cycle limits after the engine has experienced 
any of the events specified in Table 2 to paragraph (g)(1)(iii) of 
this AD, perform a BSI of the HPT rotor stage 1 and stage 2 blades.

[[Page 17681]]



       Table 2 to Paragraph (g)(1)(iii)--Conditional BSI Criteria
------------------------------------------------------------------------
  If the engine has experienced:           Then borescope inspect:
------------------------------------------------------------------------
An exhaust gas temperature (EGT)    Within 10 cycles.
 above redline.
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).
A shift in the smoothed EGT         Before further flight.
 trending data that exceeds 36
 [deg]F (20 [deg]C).
Two consecutive raw EGT trend data  Within 10 cycles.
 points that exceed 18 [deg]F (10
 [deg]C), but are less than or
 equal to 36 [deg]F (20 [deg]C),
 above the smoothed average.
Two consecutive raw EGT trend data  Before further flight.
 points that exceed 36 [deg]F (20
 [deg]C) above the smoothed
 average.
------------------------------------------------------------------------

    (iv) If the engine fails any of the BSIs required by this AD, 
before further flight, remove the engine from service.
    (2) Engines with Damaged HPT Rotor Blades, For those engines 
that fail any BSI requirements of this AD, before returning the 
engine to service, accomplish the actions required by paragraph 
(g)(2)(i) or (ii) of this AD:
    (i) Remove the LPT rotor stage 3 disk from service; or
    (ii) 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 (g)(6)(i)(A) 
through (C) of this AD.
    (3) EGT Thermocouple Probe Inspections. (i) Within 750 CSLI, or 
before further flight, whichever occurs later, inspect the EGT 
thermocouple probe for damage.

    Note 1 to paragraph (g)(3)(i):  Damage to the EGT thermocouple 
probe may be indicated by wear through the thermocouple guide sleeve 
or contact between the turbine mid-frame liner and the EGT 
thermocouple probe.

    (ii) Thereafter, within every 750 CSLI, re-inspect the EGT 
thermocouple probe for damage.
    (iii) If any EGT thermocouple probe shows wear through the 
thermocouple guide sleeve or contact between the turbine mid-frame 
liner and the EGT thermocouple probe, before further flight, remove 
and replace the EGT thermocouple probe and ensure the turbine mid-
frame liner does not contact the EGT thermocouple probe.
    (4) EGT System Resistance Checks. (i) Within 750 cycles since 
the last resistance check on the EGT system or before further 
flight, whichever occurs later, perform an EGT system resistance 
check.
    (ii) Thereafter, within every 750 cycles since the last 
resistance check, repeat the EGT system resistance check.
    (iii) If an EGT system component fails the resistance system 
check, before further flight, remove and replace, or repair the EGT 
system component.
    (5) Engine Core Vibration Survey. (i) Within 350 cycles since 
the last engine core vibration survey or before further flight, 
whichever occurs later, perform an initial engine core vibration 
survey.
    (ii) 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.
    (iii) Use a spectral/trim balance analyzer or equivalent to 
measure the N2 rotor vibration.
    (iv) If the vibration level is above 5 mils Double Amplitude, 
before further flight, remove the engine from service.
    (v) For those engines that fail any engine core vibration survey 
requirements of this AD, before returning the engine to service:
    (A) Remove the LPT rotor stage 3 disk from service; or
    (B) Perform an FPI of the inner diameter surface forward spacer 
arm of the LPT rotor stage 3 disk as specified in paragraph 
(g)(6)(i)(A) through (C) of this AD.
    (vi) Thereafter, within every 350 cycles since the last engine 
core vibration survey, perform the engine core vibration survey as 
required in paragraphs (g)(5)(i) through (v) of this AD.
    (vii) If the engine has experienced any vibration reported by 
maintenance or flight crew that is suspected to be caused by the 
engine core (N2), within 10 cycles after the report, perform the 
engine core vibration survey as required in paragraphs (g)(5)(i) 
through (v) of this AD.
    (viii) Vibration surveys carried out in an engine test cell as 
part of an engine manual performance run fulfill the vibration 
survey requirements of paragraphs (g)(5)(ii) and (iii) of this AD.
    (6) Initial and Repetitive FPI of LPT Rotor Stage 3 Disk. (i) At 
the next shop visit after accumulating 1,000 cycles since the last 
FPI of the LPT rotor stage 3 disk forward spacer arm or before 
further flight, whichever occurs later:
    (A) Clean the LPT rotor stage 3 disk forward spacer arm, 
including the use of a wet-abrasive blast, to eliminate residual or 
background fluorescence;
    (B) 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; and
    (C) If a crack or a band of fluorescence is present, before 
further flight, remove the disk from service.
    (ii) Thereafter, at each engine shop visit that occurs after 
accumulating 1,000 cycles since the last FPI of the LPT rotor stage 
3 disk forward spacer arm, clean and perform an FPI of the LPT rotor 
stage 3 disk forward spacer arm, as specified in paragraph 
(g)(6)(i)(A) through (C) of this AD.
    (7) Removal of LPT Rotor Stage 3 Disk. (i) For any installed LPT 
rotor stage 3 disk having a part number listed in Table 1 to 
paragraph (c) of this AD, at the first occurrence of any one of the 
conditions identified in paragraphs (g)(7)(i)(A) through (C) of this 
AD, remove the LPT rotor stage 3 disk from service and replace with 
LPT rotor stage 3 disk part number 2453M80P01.
    (A) For a disk that has accumulated fewer than 3,200 cycles 
since new (CSN) as of March 6, 2012 (the effective date of AD 2012-
02-07), remove the disk from service before accumulating 6,200 CSN.
    (B) For a disk that accumulated 3,200 or more CSN as of March 6, 
2012 (the effective date of AD 2012-02-07), do the actions required 
by paragraphs (g)(7)(i)(B)(1) or (2) of this AD, as applicable to 
your engine.
    (1) If the engine has a shop visit before the disk accumulates 
6,200 CSN, remove the disk from service at that shop visit.
    (2) If the engine does not have a shop visit before the disk 
accumulates 6,200 CSN, remove the disk from service at the next shop 
visit after accumulating 6,200 CSN, not to exceed 3,000 cycles from 
March 6, 2012 (the effective date of AD 2012-02-07).
    (C) Before exceeding 18 months from the effective date of this 
AD.

(h) Terminating Action

    Replacement of the LPT rotor stage 3 disk in accordance with 
paragraph (g)(7) of this AD constitutes terminating action for the 
inspections, engine checks, and vibration surveys required by 
paragraphs (g)(1) through (6) of this AD.

(i) Installation Prohibition

    After the effective date of this AD, do not install or reinstall 
onto any engine an LPT rotor stage 3 disk listed in Table 1 to 
paragraph (c) of this AD that has accumulated 6,200 CSN or more.

(j) Definitions

    For the purposes of this AD:
    (1) An EGT above redline is a confirmed over-temperature 
indication that is not a result of EGT system error.
    (2) 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.

    Note 2 to paragraph (j)(2): You can find further guidance about 
evaluating EGT trend data in GE Company Service Rep Tip 373 
``Guidelines For Parameter Trend Monitoring.''

    (3) An engine shop visit is the induction of an engine into the 
shop, 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;

[[Page 17682]]

    (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; and
    (v) Induction of an engine into a shop solely for replacement of 
the fan forward case.
    (4) 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.

(k) Credit for Previous Actions

    You may take credit for the actions required by paragraph (g) of 
this AD if they were performed before the effective date of this AD 
using GE Service Bulletin (SB) No. CF6-50 SB 72-1315, Initial Issue, 
dated June 3, 2011, or GE SB No. CF6-50 SB 72-1315, Revision 1, 
dated June 30, 2011.

(l) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, ECO Branch, FAA, has the authority to approve 
AMOCs for this AD, if requested using the procedures found in 14 CFR 
39.19. In accordance with 14 CFR 39 19, send your request to your 
principal inspector or local Flight Standards District Office, as 
appropriate. If sending information directly to the manager of the 
certification office, send it to the attention of the person 
identified in paragraph (m) of this AD and email it to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.
    (3) AMOCs approved previously 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 as AMOCs for the 
corresponding provisions of this AD.

(m) Related Information

    For more information about this AD, contact Sungmo Cho, Aviation 
Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, 
MA 01803; phone: (781) 238-7241; email: [email protected].

(n) Material Incorporated by Reference

    None.

    Issued on February 17, 2023.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-05472 Filed 3-23-23; 8:45 am]
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