Airworthiness Directives; General Electric Company Turbofan Engines

[Federal Register Volume 86, Number 178 (Friday, September 17, 2021)]
[Rules and Regulations]
[Pages 51792-51795]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-20042]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0919; Project Identifier 2019-NE-24-AD; Amendment 
39-21714; AD 2021-18-13]
RIN 2120-AA64


Airworthiness Directives; General Electric Company Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
General Electric Company (GE) CF34-8 model turbofan engines with a 
certain outer shell combustion liner (combustion outer liner shell) 
installed. This AD was prompted by two in-flight engine shutdowns 
(IFSDs) that occurred as a result of failures of the combustion outer 
liner shell. This AD requires a borescope inspection (BSI) or visual 
inspection of the combustion outer liner shell and, depending on the 
results of the inspection, possible replacement of the combustion outer 
liner shell. The FAA is issuing this AD to address the unsafe condition 
on these products.

DATES: This AD is effective October 22, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of certain publications listed in this AD as of October 22, 
2021.

ADDRESSES: For service information identified in this final rule, 
contact General Electric Company, GE Aviation, Room 285, 1 Neumann Way, 
Cincinnati, OH 45215; phone: (513) 552-3272; email: 
[email protected]. You may view this service information at 
the FAA, Airworthiness Products Section, Operational Safety Branch, 
1200 District Avenue, Burlington, MA 01803. For information on the 
availability of this material at the FAA, call (781) 238-7759. It is 
also available at https://www.regulations.gov by searching for and 
locating Docket No. FAA-2019-0919.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2019-0919; 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: Scott Stevenson, Aviation Safety 
Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; 
phone: (781) 238-7132; fax: (781) 238-7199; email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to all CF34-8C1, CF34-8C5, 
CF34-8C5A1, CF34-8C5B1, CF34-8C5A2, CF34-8C5A3, CF34-8E2, CF34-8E2A1, 
CF34-8E5, CF34-8E5A1, CF34-8E5A2, CF34-8E6, and CF34-8E6A1 model 
turbofan engines with a certain combustion outer liner shell installed. 
The NPRM published in the Federal Register on January 10, 2020 (85 FR 
1292). The NPRM was prompted by reports of two IFSDs on GE CF34-8C and 
-8E model turbofan engines. These IFSDs were due to the cracking and 
collapsing of the combustion outer liner shell, which resulted in 
thermal distress of the high-pressure turbine and low-pressure turbine 
(LPT) including burn-through of the LPT case. In the NPRM, the FAA 
proposed to require a BSI or visual inspection of the combustion outer 
liner shell and, depending on the results of the inspection, possible 
replacement of the combustion outer liner shell. The FAA is issuing 
this AD to address the unsafe condition on these products.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from four commenters. The commenters were 
Horizon Air, Japan Airlines, Endeavor Air, and the Air Line Pilots 
Association, International (ALPA). The following presents the comments 
received on the NPRM and the FAA's response to each comment.

Request To Change the Initial Compliance Time

    Horizon Air requested the FAA revise the initial inspection 
threshold in proposed paragraph (g)(2) of the NPRM to ``17,499 flight 
hours (FHs) time since new (TSN) or time since repair (TSR), or 12,000 
flight cycles (FCs) TSN or TSR, whichever occurs later.'' Horizon Air 
reasoned that the initial inspection threshold in paragraph (g)(2) of 
the proposed AD would unfairly penalize operators, like Horizon Air, 
with high FH to FC ratios. Horizon Air further stated that using the 
higher FH to FC ratios, the proposed 17,499 FHs TSN or TSR inspection 
threshold would equate to approximately 11,000 engine FCs. This FC 
value is substantially below the GE targeted initial engine shop visit 
threshold of 12,000 to 14,000 FCs and would potentially result in a 
significant increase in the number of engine shop visits over the 6- to 
12-year operating lifespan of each engine.
    The FAA partially agrees. While the failure mode is partially 
related to FCs, the compliance is published in FHs to align with 
existing maintenance intervals. Incorporating both measures as 
intervals into this AD is impractical; however, operators may request 
an alternative method of compliance (AMOC) in accordance with the 
procedures specified in paragraph (k) of this AD to use alternate 
intervals. The FAA did not change this AD as a result of this comment.

Request To Change the Installation Prohibition

    Horizon Air requested the FAA revise paragraph (h), Installation 
Prohibition, as proposed in the NPRM, so it does not conflict with the 
proposed required actions specified in paragraph (g)(1) of the NPRM. 
Horizon Air stated that paragraph (h) of the proposed AD prohibits 
installation of a combustion outer liner shell with greater than 17,500 
FHs TSN or TSR, without first inspecting it in accordance with 
paragraph (g)(1) of the proposed AD. However, paragraph (g)(1) of the 
proposed AD requires inspection of the combustion outer liner shell 
within 500 engine FHs TSN or TSR for those combustion outer liner 
shells that have accumulated 17,500 FHs TSN or TSR. Horizon Air 
concluded that the 18,000 FHs TSN or TSR limitation specified in 
paragraph (g)(1) of the proposed AD conflicts with the 17,500 FHs TSN 
or

[[Page 51793]]

TSR limit specified in paragraph (h) of the proposed AD.
    The FAA disagrees. The initial inspection threshold is 17,500 FHs 
for affected engines. This AD provides a grace period of 500 FHs for 
in-service engines to prevent the unintentional grounding of airplanes 
with affected engines. The FAA did not change this AD as a result of 
this comment.

Request To Include a Terminating Action

    Horizon Air requested the FAA petition GE for a terminating action 
to the inspection requirements in the proposed AD. Horizon Air 
commented the financial cost and maintenance burden of performing the 
repetitive inspections are significant.
    The FAA disagrees. The FAA considers this AD to be interim action 
and will consider further rulemaking if the manufacturer develops a 
terminating action. The FAA included all estimated costs in the Costs 
of Compliance section in the preamble of this AD. The FAA did not 
change this AD as a result of this comment.

Request To Revise Service Information References

    Horizon Air, Japan Airlines, and Endeavor Air requested the FAA 
update references to GE CF34-8E Alert Service Bulletin (SB) 72-A0221 
and GE CF34-8C Alert SB 72-A0335 in the Required Actions section, 
paragraph (g), of the proposed AD. Japan Airlines requested that GE 
CF34-8E-AL S/B 72-A0221, Original Issue, dated June 27, 2019, be added 
to the compliance paragraphs because the Original Issue and R01 have 
the same inspection methods and limits. Horizon Air requested that the 
FAA reference only GE CF34-8E Alert SB 72-A0221 R01 in paragraph (g) of 
the proposed AD and add a Previous Credit section to allow previous 
compliance using the Original Issue. Endeavor Air requested that the 
FAA reference the latest revision of GE CF34-8C Alert SB 72-A0335 in 
proposed paragraph (g). Endeavor Air indicated that GE planned to issue 
R02 of CF34-8C Alert SB 72-A0335 on February 24, 2020.
    The FAA agrees to reference the latest revision of these Alert SBs, 
which is R02 for both GE CF34-8C Alert SB 72-A0335 and GE CF34-8E Alert 
SB 72-A0221, in paragraph (g) of this AD. The FAA disagrees with the 
need to reference prior revisions of these Alert SBs in paragraphs (g) 
of this AD but agrees to add Credit for Previous Actions, paragraph 
(j), to this AD to allow credit for performing inspections prior to the 
effective date of this AD. These changes impose no additional burden on 
operators who are required to comply with this AD.

Request To Clarify Compliance

    Japan Airlines requested that the FAA clarify whether the 
inspection should occur ``before'' or ``within'' 500 FHs after the 
effective date of this AD. Japan Airlines reasoned that the service 
bulletin specifies to inspect ``before'' 500 FHs, while the NPRM 
proposed to inspect ``within'' 500 FHs.
    The FAA agrees. The FAA revised Required Actions, paragraphs (g)(1) 
and (2) of this AD to specify, ``before accumulating 500 engine FHs.''

Support for the AD

    ALPA expressed support for the NPRM as written.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. Except for minor editorial changes, and 
any other changes described previously, this AD is adopted as proposed 
in the NPRM. None of the changes will increase the economic burden on 
any operator.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed General Electric CF34-8C Alert SB 72-A0335 R02 and 
General Electric CF34-8E Alert SB 72-A0221 R02, both dated February 25, 
2020. The Alert SBs specify procedures for performing a BSI of the 
combustion outer liner shell. These documents are distinct since they 
apply to different engine models. This service information is 
reasonably available because the interested parties have access to it 
through their normal course of business or by the means identified in 
ADDRESSES.

Interim Action

    The FAA considers this AD to be an interim action. If final action 
is later identified, the FAA might consider further rulemaking.

Costs of Compliance

    The FAA estimates that this AD affects 1,535 engines installed on 
airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
BSI or visually inspect the combustion  3 work-hours x $85 per                $0            $255        $391,425
 outer liner shell.                      hour = $255.
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do any necessary 
replacements that would be required based on the results of the 
inspection. The agency has no way of determining the number of engines 
that might need this replacement:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replace the combustion outer liner shell......  812 work-hours x $85 per hour =          $80,000        $149,020
                                                 $69,020.
----------------------------------------------------------------------------------------------------------------


[[Page 51794]]

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

    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 adding the following new airworthiness 
directive:

2021-18-13 General Electric Company: Amendment 39-21714; Docket No. 
FAA-2019-0919; Project Identifier 2019-NE-24-AD.

(a) Effective Date

    This airworthiness directive (AD) is effective October 22, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to General Electric Company (GE) CF34-8C1, CF34-
8C5, CF34-8C5A1, CF34-8C5B1, CF34-8C5A2, CF34-8C5A3, CF34-8E2, CF34-
8E2A1, CF34-8E5, CF34-8E5A1, CF34-8E5A2, CF34-8E6, and CF34-8E6A1 
model turbofan engines with an outer shell combustion liner 
(combustion outer liner shell), part number (P/N) 4124T04G04, P/N 
4124T04G05, or P/N 5159T35G02, installed.

(d) Subject

    Joint Aircraft System Component (JASC) Code 7240, Turbine Engine 
Combustion Section.

(e) Unsafe Condition

    This AD was prompted by two in-flight engine shutdowns (IFSDs) 
that occurred as a result of failures of the combustion outer liner 
shell. The FAA is issuing this AD to prevent failure of the 
combustion outer liner shell. The unsafe condition, if not 
addressed, could result in burn-through of the low-pressure turbine 
case, engine fire, and damage to the airplane.

(f) Compliance

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

(g) Required Actions

    (1) For an affected engine with a combustion outer liner shell 
that on the effective date of this AD has accumulated 17,500 flight 
hours (FHs) or greater time since new (TSN), or time since repair 
(TSR), perform an initial borescope inspection (BSI) or visual 
inspection of the combustion outer liner shell for cracks before 
accumulating 500 engine FHs after the effective date of this AD.
    (i) For GE CF34-8C engines, inspect using the Accomplishment 
Instructions, paragraphs 3.A.(4) and 3.A.(5), of GE CF34-8C Alert 
Service Bulletin (SB) 72-A0335 R02, dated February 25, 2020 (CF34-8C 
Alert SB 72-A0335).
    (ii) For GE CF34-8E engines, inspect using the Accomplishment 
Instructions, paragraphs 3.A.(4) and 3.A.(5), of GE CF34-8E Alert SB 
72-A0221 R02, dated February 25, 2020 (CF34-8E Alert SB 72-A0221).

    Note 1 to paragraph (g)(1): GE has identified the service 
information as an ``Alert Service Bulletin,'' which is stated only 
in the body of the Alert SB.

    (2) For an affected engine with a combustion outer liner shell 
that on the effective date of this AD has accumulated 17,499 FHs or 
fewer TSN or TSR, before accumulating 500 engine FHs after the 
combustion outer liner shell has accumulated 17,500 FHs TSN or TSR, 
perform an initial BSI or visual inspection on the combustion outer 
liner shell for cracks.
    (i) For GE CF34-8C engines, inspect using the Accomplishment 
Instructions, paragraphs 3.A.(4) and 3.A.(5), of CF34-8C Alert SB 
72-A0335.
    (ii) For GE CF34-8E engines, inspect using the Accomplishment 
Instructions paragraphs 3.A.(4) and 3.A.(5), of CF34-8E Alert SB 72-
A0221.
    (3) For an affected engine with a combustion outer liner shell 
for which it is not possible to determine the TSN or TSR, use the 
engine FHs since new to determine when to perform the initial BSI or 
visual inspection.
    (4) After the effective date of this AD, and after the initial 
inspection required by paragraph (g)(1) or (2) of this AD, re-
inspect or remove the combustion outer liner shell using inspection 
criteria as follows:
    (i) For GE CF34-8C engines, use Table 1 of CF34-8C Alert SB 72-
A0335.
    (ii) For GE CF34-8E engines, use Table 1 of CF34-8E Alert SB 72-
A0221.

(h) Installation Prohibition

    After the effective date of this AD, do not install a combustion 
outer liner shell with greater than 17,500 FHs TSN or TSR without 
first inspecting the combustion outer liner shell in accordance with 
paragraph (g)(1) of this AD.

(i) Definition

    For the purpose of this AD, ``time since repair (TSR)'' is the 
amount of FHs accumulated on the combustion outer liner shell since 
performing GEK 105091 or GEK 112031, 72-44-06, REPAIR 023.

(j) Credit for Previous Actions

    You may take credit for any initial BSI or visual inspection of 
the combustion outer liner shell required by paragraphs (g)(1) and 
(2) of this AD if you performed the initial BSI or visual inspection 
before the effective date of this AD using:
    (1) GE CF34-8C-AL S/B 72-A0335, Original Issue, dated June 27, 
2019;
    (2) GE CF34-8C Alert SB 72-A0335 R01, dated September 23, 2019;
    (3) GE CF34-8E-AL S/B 72-A0221, Original Issue, dated June 27, 
2019; or
    (4) GE CF34-8E Alert SB 72-A0221 R01, dated September 23, 2019.

(k) 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 Related Information. You may email your request 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.

[[Page 51795]]

(l) Related Information

    For more information about this AD, contact Scott Stevenson, 
Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, 
Burlington, MA 01803; phone: (781) 238-7132; fax: (781) 238-7199; 
email: [email protected].

(m) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (i) GE CF34-8C Alert Service Bulletin (SB) 72-A0335 R02, dated 
February 25, 2020.
    (ii) GE CF34-8E Alert SB 72-A0221 R02, dated February 25, 2020.
    (3) For GE 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].
    (4) You may view this service information at FAA, Airworthiness 
Products Section, Operational Safety Branch, 1200 District Avenue, 
Burlington, MA 01803. For information on the availability of this 
material at the FAA, call (781) 238-7759.
    (5) You may view this 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, email: [email protected], or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on August 26, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-20042 Filed 9-16-21; 8:45 am]
BILLING CODE 4910-13-P

The complete text was extracted from the official GovInfo HTML edition for this publication. Acquired 2026-10-09T01:48:15.426856+00:00. Text extraction preserves the recorded source wording; it does not determine current requirements.

Open the captured official edition

Source SHA-256

62937f65648030d5749e580a11bd04626002dac343012a23d068f0b2cf823cd5

Text SHA-256

e2b2918645159b8d00762fcd6878028f4b4185ab3bebcccb4a728fd01dff3529