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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2024-1885; Project Identifier AD-2023-00995-E]
RIN 2120-AA64
Airworthiness Directives; General Electric Company Engines
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Supplemental notice of proposed rulemaking (SNPRM).
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SUMMARY: The FAA is revising a notice of proposed rulemaking (NPRM)
that applied to certain General Electric Company (GE) Model CF34-
10E2A1, CF34-10E6, CF34-10E6A1, CF34-10E7, and CF34-10E7-B engines
having certain high-pressure turbine (HPT) front rotating air seals
installed. This action revises the NPRM by adding Model CF34-10E5 and
CF34-10E5A1 engines to the applicability. The FAA is proposing this
airworthiness directive (AD) to address the unsafe condition on these
products. Since these actions would impose an additional burden over
those in the NPRM, the agency is requesting comments on this SNPRM.
DATES: The FAA must receive comments on this SNPRM by June 9, 2025.
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 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.
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2024-1885; 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 SNPRM, any comments received, and other
information. The street address for Docket Operations is listed above.
Material Incorporated by Reference:
For GE material identified in this SNPRM, contact GE, 1
Neumann Way, Cincinnati, OH 45215; phone: (513) 552-3272; email:
aviation.fleetsupport@ge.com; website: ge.com.
You may view this material 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 (817) 222-5110.
FOR FURTHER INFORMATION CONTACT: Alexei Marqueen, Aviation Safety
Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone:
(781) 238-7178; email: alexei.t.marqueen@faa.gov.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under the ADDRESSES section. Include "Docket No. FAA-2024-1885;
Project Identifier AD-2023-00995-E" at the beginning of your comments.
The most helpful comments reference a specific portion of the proposal,
explain the reason for any recommended change, and include supporting
data. The FAA will consider all comments received by the closing date
and may again revise the proposal because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
regulations.gov, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this SNPRM.
Confidential Business Information
CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this SNPRM contain
commercial or financial information that is customarily treated as
private, that you actually treat as private, and that is relevant or
responsive to this SNPRM, it is important that you clearly designate
the submitted comments as CBI. Please mark each page of your submission
containing CBI as "PROPIN." The FAA will treat such marked
submissions as confidential under the FOIA, and they will not be placed
in the public docket of this SNPRM. Submissions containing CBI should
be sent to Alexei Marqueen, Aviation Safety Engineer, FAA, 2200 South
216th Street, Des Moines, WA 98198. Any commentary that the FAA
receives which is not specifically designated as CBI will be placed in
the public docket for this rulemaking.
Background
The FAA issued an NPRM to amend 14 CFR part 39 by adding an AD that
would apply to certain GE Model CF34-10E2A1, CF34-10E6, CF34-10E6A1,
CF34-10E7, and CF34-10E7-B engines with certain part numbered high-
pressure turbine (HPT) front rotating air seals installed. The NPRM was
published in the Federal Register on July 24, 2024 (89 FR 59860). The
NPRM was prompted by a report of indications found in certain HPT front
rotating air seals at the rabbet surface where the affected part
interacts with the HPT rotor disk tabs. The manufacturer investigated
and determined that the indications were caused by a high edge of
contact stress between the HPT rotor disk and the rabbet surface of the
HPT front rotating air seal. In the NPRM, the FAA proposed to require
repetitive FPIs to detect indications or linear indications (any
indication that is four times longer than the width of that same
indication) in the HPT front rotating air seal and, if necessary,
replacement of the HPT front rotating air seal or HPT rotor disk with
parts eligible for installation. Additionally, replacing the HPT front
rotating air seal with an updated design part constitutes as a
terminating action for the proposed AD.
Actions Since the NPRM Was Issued
Since the FAA issued the NPRM, the FAA has determined changes to
the applicability are necessary, primarily based on comments received
from several commenters and additional review.
Comments
The FAA received comments on the NPRM from Japan Airlines and the
Air Line Pilots Association, International (ALPA). ALPA supported the
NPRM without change. The agency considered the comments received from
Japan Airlines and the following discussion presents these comments and
the FAA's response.
Request To Update the Applicability
Japan Airlines suggested that the applicability of the NPRM include
Models CF34-10E5 and CF34-10E5A1, because the effectivity of GE CF34-
10E Service Bulletin 72-0341 R02, dated September 24, 2021 (GE SB 72-
0341 R02) applies to all CF34-10E engines with an installed high-
pressure turbine (HPT) front rotating air seals, part number (P/N)
1865M49P04, P/N 2448M30P02, or P/N 2448M30P03. The FAA agrees and has
revised paragraph (c) to include Model CF34-10E5 and CF34-10E5A1 engines.
Request To Revise Compliance Time
Japan Airlines also requested that the compliance time be revised
to match the service bulletin in that the proposed actions be when the
HPT rotor assembly is exposed instead of disassembled from the core
module assembly. Japan Airlines stated that the compliance time in
paragraph (g)(1) of the proposed AD shows to replace "at the next
exposure of the HPT rotor assembly" and paragraph (i)(1) of the
proposed AD shows that a "piece part exposure" is when the HPT front
rotating air seal is disassembled from the HPT rotor assembly. If the
FAA's intent was to match the service bulletin, Japan Airlines
suggested that the compliance time of paragraph (g)(1) of the proposed
AD be changed to "at the next exposure of the HPT rotor assembly and
each exposure thereafter; and the definition in paragraph (i)(1) of the
proposed AD be changed to "exposure of the HPT rotor assembly is when
the HPT rotor assembly is disassembled from the core module assembly.
The FAA agrees and has revised paragraph (g)(1) to use "at next
exposure of the HPT rotor assembly" and paragraph (i)(1) to define
"exposure of HPT rotor assembly" to match the intent of the service bulletin.
FAA's Determination
The FAA is proposing this AD after determining the unsafe condition
described previously is likely to exist or develop in other products of
the same type design. Certain changes described above expand the scope
of the NPRM. As a result, it is necessary to reopen the comment period
to provide additional opportunity for the public to comment on this SNPRM.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed GE SB 72-0341 R02. This material specifies
procedures for repetitive FPIs and eddy current inspections of certain
HPT front rotating air seals for indications or linear indications and,
if necessary, replacement of the affected HPT front rotating air seals
or the HPT rotor disk with parts eligible for installation. This
material is reasonably available because the interested parties have
access to it through their normal course of business or by the means
identified in ADDRESSES.
Proposed AD Requirements in This SNPRM
This proposed AD would require, at the next exposure of the HPT
rotor assembly, repetitive FPIs to detect indications or linear
indications (any indication that is four times longer than the width of
that same indication) in the HPT front rotating air seal and, if
necessary, replacement of the HPT front rotating air seal or HPT rotor
disk with parts eligible for installation. Additionally, replacing the
HPT front rotating air seal with an updated design part constitutes
terminating action for the proposed AD.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, affects 228
engines installed on airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:
Estimated Costs
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ACTION
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LABOR COST
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PARTS COST
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COST PER PRODUCT
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COST ON U.S. OPERATORS
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| FPI of the HPT front rotating air seal |
8 work-hours x $85 per hour = $680. |
$0
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$680
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$155,040
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The FAA estimates the following costs to do any necessary
replacements that would be required based on the results of the
proposed inspections. The agency has no way of determining the number
of engines that might need these replacements:
On-Condition Costs
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ACTION
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LABOR COST
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PARTS COST
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COST PER PRODUCT
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| Replace HPT front rotating air seal. |
8 work-hours x $85 per hour = $680. |
$332,000
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$332,680
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| Replace HPT rotor disk. |
8 work-hours x $85 per hour = $680. |
341,800
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342,480
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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 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 this proposed regulation:
(1) Is not a "significant regulatory action" under Executive Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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 adding the following new airworthiness
directive:
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