[Federal Register Volume 90, Number 220 (Tuesday, November 18, 2025)]
[Proposed Rules]
[Pages 51590-51592]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-20089]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-3998; Project Identifier AD-2025-00432-E]
RIN 2120-AA64
Airworthiness Directives; General Electric Company Engines
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain General Electric Company (GE) Model CF34-8C1, CF34-8C5,
CF34-8C5A1, CF34-8C5A2, CF34-8C5B1, CF34-8E2, CF34-8E2A1, CF34-8E5,
CF34-8E5A1, CF34-8E5A2, CF34-8E5A2HA, CF34-8E6, and CF34-8E6A1 engines.
This proposed AD was prompted by reports of in-flight ``Engine
Degraded'' messages from the engine indicating and crew alerting system
(EICAS) due to corrosion of the variable geometry (VG) system actuator.
This proposed AD would require removing certain electronic engine
control (EEC) full authority digital electronic control (FADEC)
software versions from service and installing an updated EEC FADEC
software that is eligible for installation. The FAA is proposing this
AD to address the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by January 2,
2026.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
[[Page 51591]]
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-2025-3998; 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 NPRM, any comments received, and other
information. The street address for Docket Operations is listed above.
FOR FURTHER INFORMATION CONTACT: Daiyun Fang, Aviation Safety Engineer,
FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: (206) 910-
0063; email: [email protected].
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments using a method listed
under the ADDRESSES section. Include ``Docket No. FAA-2025-3998;
Project Identifier AD-2025-00432-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 revise this 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 NPRM.
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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to
Daiyun Fang, 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 was notified of three separate events involving airplanes
with Model GE CF34-8C5 engines installed in which ``Engine Degraded''
messages were received from the EICAS during flight. A subsequent
investigation by the manufacturer revealed that these engines had been
operated infrequently over the two-year period prior to these events
and stored in close proximity to a saltwater coastline. The
investigation further revealed the variable geometry (VG) actuation
lever arms were stuck due to corrosion between the high-pressure
compressor case and vane bushings, which increased the VG actuation
loads and slowed the VG response. As a result of this increase, the VG
command and actual positions exceeded acceptable disagreement
parameters, triggering an EICAS ``Engine Degraded'' message. In
response to the ``Engine Degraded'' message, the manufacturer and FAA
determined that certain versions of the EEC FADEC software installed on
GE CF34-8E and GE CF34-8C engines can potentially reduce the engine to
idle and lock the throttle until the engine is shut down and restarted.
This condition, if not addressed, could result in failure of one or
more engines, loss of engine thrust control, and consequent reduced
control of the airplane.
FAA's Determination
The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.
Proposed AD Requirements in This NPRM
This proposed AD would require removal of certain EEC FADEC
software versions from service and installing updated EEC FADEC
software that is eligible for installation.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 3,040 engines installed on airplanes of U.S. registry. The FAA
estimates that 70 of these affected engines will also require an
additional memory upgrade of the EEC FADEC software from a three memory
sector configuration to a seven memory sector configuration.
The FAA estimates the following costs to comply with this proposed
AD:
Estimated Costs
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Cost per Cost on U.S.
Action Labor cost Parts cost product operators
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Remove and install EEC FADEC software.... 8 work-hours x $85 per hour $660 $1,340 $4,073,600
= $680.
Upgrade EEC FADEC software to seven 8 work-hours x $85 per hour 49,000 49,680 3,477,600
sectors (70 engines). = $680.
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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
[[Page 51592]]
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
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:
General Electric Company: Docket No. FAA-2025-3998; Project
Identifier AD-2025-00432-E.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by January 2, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to the General Electric Company (GE) Model
engines identified in paragraphs (c)(1) and (2) of this AD.
(1) CF34-8C1, CF34-8C5, CF34-8C5A1, CF34-8C5A2, and CF34-8C5B1
engines with an electronic engine control (EEC) full authority
digital electronic control (FADEC) part number (P/N) 4120T00P29,
4120T00P30, 4120T00P37, 4120T00P38, 4120T00P45, 4120T00P46,
4120T00P53, 4120T00P54, 4120T00P57, or 4120T00P58 installed.
(2) CF34-8E2, CF34-8E2A1, CF34-8E5, CF34-8E5A1, CF34-8E5A2,
CF34-8E5A2HA, CF34-8E6, and CF34-8E6A1 engines with an EEC FADEC P/N
4120T00P42 (VIN 111E9320G43), P/N 4120T00P44 (VIN 111E9320G45), P/N
4120T00P48 (VIN 111E9320G49), P/N 4120T00P50 (VIN 111E9320G51), or
P/N 4120T00P60 (VIN 111E9320G61) installed.
(d) Subject
Joint Aircraft System Component (JASC) Code 7230, Turbine Engine
Compressor Section.
(e) Unsafe Condition
This AD was prompted by an ``Engine Degraded'' message received
in-flight from the engine indicating and crew alerting system, due
to corrosion of the variable geometry system actuator. The FAA is
issuing this AD to prevent EEC FADEC software from automatically
locking the engine at idle until it is restarted. The unsafe
condition, if not addressed, could result in failure of one or more
engines, loss of engine thrust control, and consequent reduced
control of the airplane.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
(1) For Group 1 engines, within 12 months after the effective
date of this AD, replace any EEC FADEC software version that is
V6.50 or earlier with an EEC FADEC software version that is eligible
for installation.
(2) For Group 2 engines, within 12 months after the effective
date of this AD, replace any EEC FADEC software version that is
V5.60 or earlier with an EEC FADEC software version that is eligible
for installation.
(h) Definitions
For the purpose of this AD, the following definitions apply:
(1) ``Group 1 engines'' are GE Model CF34-8C1, CF34-8C5, CF34-
8C5A1, CF34-8C5A2, and CF34-8C5B1 engines.
(2) ``Group 2 engines'' are GE Model CF34-8E2, CF34-8E2A1, CF34-
8E5, CF34-8E5A1, CF34-8E5A2, CF34-8E5A2HA, CF34-8E6, and CF34-8E6A1
engines.
(3) An ``EEC FADEC software version that is eligible for
installation'' on Group 1 engines is any software version that is
V6.60 or later approved version.
(4) An ``EEC FADEC software version that is eligible for
installation'' on Group 2 engines is any software version that is
V5.70 or later approved version.
(i) Alternative Methods of Compliance (AMOCs)
(1) The Manager, AIR-520 Continued Operational Safety 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 AIR-520 Continued Operational
Safety Branch, send it to the attention of the person identified in
paragraph (j) of this AD and email 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.
(j) Additional Information
For more information about this AD, contact Daiyun Fang,
Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines,
WA 98198; phone: (206) 910-0063; email: [email protected].
(k) Material Incorporated by Reference
None.
Issued on November 6, 2025.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft
Certification Service.
[FR Doc. 2025-20089 Filed 11-17-25; 8:45 am]
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