[Federal Register Volume 90, Number 225 (Tuesday, November 25, 2025)]
[Proposed Rules]
[Pages 53238-53242]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-20852]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-5032; Project Identifier AD-2025-01042-R]
RIN 2120-AA64
Airworthiness Directives; Airbus Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD)
2025-06-04, which applies to all Airbus Helicopters Model AS350B,
AS350B1, AS350B2, AS350B3, AS350BA,
[[Page 53239]]
AS350D, AS355E, AS355F, AS355F1, AS355F2, AS355N, AS355NP, EC130B4, and
EC130T2 helicopters. AD 2025-06-04 requires repetitively inspecting the
main gearbox (MGB) bevel wheel and the MGB magnetic plug for particles
and performing corrective actions if applicable and prohibits
installing an affected MGB unless certain requirements are met. Since
the FAA issued AD 2025-06-04, the FAA determined that AD 2025-06-04
contains errors in the interval compliance times. This proposed AD
would continue to require the actions of AD 2025-06-04 and revise the
interval compliance times. 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 9,
2026.
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-2025-5032; 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, the mandatory continuing airworthiness
information (MCAI), any comments received, and other information. The
street address for Docket Operations is listed above.
Material Incorporated by Reference:
For European Union Aviation Safety Agency (EASA) material
identified in this proposed AD, contact EASA, Konrad-Adenauer-Ufer 3,
50668 Cologne, Germany; phone: +49 221 8999 000; email:
[email protected]; website easa.europa.eu. You may find this material
on the EASA website at ad.easa.europa.eu.
You may view this material at the FAA, Office of the
Regional Counsel, Southwest Region, 10101 Hillwood Parkway, Room 6N-
321, Fort Worth, TX 76177. For information on the availability of this
material at the FAA, call (817) 222-5110.
FOR FURTHER INFORMATION CONTACT: Dan McCully, Aviation Safety Engineer,
FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (404)
474-5548; 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-2025-5032;
Project Identifier AD-2025-01042-R'' 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 Dan
McCully, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590. 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 AD 2025-06-04, Amendment 39-22992 (90 FR 14723,
April 4, 2025) (AD 2025-06-04), for all Airbus Helicopters Model
AS350B, AS350B1, AS350B2, AS350B3, AS350BA, AS350D, AS355E, AS355F,
AS355F1, AS355F2, AS355N, AS355NP, EC130B4, and EC130T2 helicopters. AD
2025-06-04 was prompted by EASA AD 2023-0044, dated February 28, 2023
(EASA AD 2023-0044) (also referred to as the MCAI), issued by EASA,
which is the Technical Agent for the Member States of the European
Union. The MCAI states that after a fleet design review for detection
of particles in the MGB, it was determined that additional maintenance
actions are necessary to improve detection of particles in MGB that
have certain part-numbered planet gear bearings installed. AD 2025-06-
04 requires repetitively inspecting the MGB bevel wheel and the MGB
magnetic plug for the presence of particles, close monitoring of the
MGB magnetic plug if particles are detected, and replacing the
epicyclic module if necessary. The AD also prohibits installing an
affected MGB unless certain requirements are met. The agency issued AD
2025-06-04 to detect and correct the presence of particles in the MGB
which, if not addressed, could result in reduced or loss of control of
the helicopter.
Actions Since AD 2025-06-04 Was Issued
Since the FAA issued AD 2025-06-04, the FAA determined that there
are errors in the interval compliance times in Table 1 to paragraph
(h)(6)(i) of AD 2025-06-04. Airbus Helicopters Model AS350B, AS350B1,
AS350BA, AS350D, AS355E, AS355F, AS355F1, AS355F2, AS355N, and AS355NP
helicopters should have an interval compliance time of 100 hours time-
in-service (TIS) instead of 30 hours TIS. Also, Airbus Helicopters
Model EC130B4 helicopters should have an interval compliance time of
100 hours TIS instead of 150 hours TIS.
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.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed EASA AD 2023-0044, which specifies procedures for
repetitive borescope visual inspections of the bevel wheel of the
affected MGB for particles, collecting and analyzing any particles
detected, and depending on the results, accomplishing further actions,
accomplishing corrective action in accordance with the ASB, or
contacting AH [Airbus Helicopters] for further corrective action. EASA
AD 2023-0044 also specifies procedures for accomplishing a borescope
visual
[[Page 53240]]
inspection of the bevel wheel of the affected MGB for particles
following the detection of any particles at the MGB magnetic plug
during accomplishment of certain maintenance tasks and depending on the
results, taking corrective action. EASA AD 2023-0044 also prohibits
installing an affected MGB on any helicopter unless certain
requirements are met.
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 the ADDRESSES section.
Proposed AD Requirements in This NPRM
This proposed AD would continue to require the actions of AD 2025-
06-04, except that this proposed AD would revise the interval
compliance times. The actions proposed in this AD are specified in EASA
AD 2023-0044, described previously, as incorporated by reference,
except for any differences identified as exceptions in the regulatory
text of this proposed AD. See ``Differences Between this Proposed AD
and the MCAI'' for a discussion of the general differences included in
this proposed AD.
Differences Between This Proposed AD and the MCAI
The MCAI applies to Model AS350BB helicopters, whereas this
proposed AD would not because that model does not have an FAA type
certificate.
Where Note 1 in the material referenced in the MCAI specifies the
option of 1 mechanical technician and 1 crew member, for this proposed
AD, the pilot is only permitted to turn the tail rotor (b) because the
other actions specified in the note must be accomplished by persons
authorized under 14 CFR 43.3. Therefore, for the purposes of this
proposed AD, the owner/operator (pilot) may turn the tail rotor (b) and
must enter compliance with the applicable paragraph of this proposed AD
in the helicopter maintenance records in accordance with 14 CFR 43.9(a)
and 91.417(a)(2)(v). The pilot may perform this action because it only
involves turning the tail rotor (b). This action can be performed
equally well by a pilot or a mechanic. This action is an exception to
the FAA's standard maintenance regulations.
This proposed AD would not require complying with paragraph (2) of
the MCAI. Instead, this proposed AD would require repetitively
inspecting the MGB magnetic plug for particles and, if there is any
particle, accomplishing a borescope visual inspection, as specified in
paragraphs (h)(6)(i) and (ii) of this proposed AD.
Where the material referenced in the MCAI specifies contacting
Airbus Helicopters for a certain action, this proposed AD would require
accomplishing action in accordance with a method approved by the FAA,
EASA, or Airbus Helicopters' EASA Design Organization Approval.
Explanation of Required Compliance Information
In the FAA's ongoing efforts to improve the efficiency of the AD
process, the FAA developed a process to use some civil aviation
authority (CAA) ADs as the primary source of information for compliance
with requirements for corresponding FAA ADs. The FAA has been
coordinating this process with manufacturers and CAAs. As a result, the
FAA proposes to incorporate EASA AD 2023-0044 by reference in the FAA
final rule. This proposed AD would, therefore, require compliance with
EASA AD 2023-0044 in its entirety through that incorporation, except
for any differences identified as exceptions in the regulatory text of
this proposed AD. Using common terms that are the same as the heading
of a particular section in EASA AD 2023-0044 does not mean that
operators need comply only with that section. For example, where the AD
requirement refers to ``all required actions and compliance times,''
compliance with this AD requirement is not limited to the section
titled ``Required Action(s) and Compliance Time(s)'' in EASA AD 2023-
0044. Material required by EASA AD 2023-0044 for compliance will be
available at www.regulations.gov by searching for and locating Docket
No. FAA-2025-5032 after the FAA final rule is published.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 522 helicopters of U.S. registry.
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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Visually inspect MGB bevel wheel... 1 work-hour x $85 per hour $0 $85 $44,370
= $85.
Repetitively inspect magnetic plugs 1 work-hour x $85 per hour 0 85 44,370
of the MGB. = $85.
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The new requirements of this proposed AD add no additional economic
burden.
The FAA estimates the following costs to do any on-condition
actions that would be required based on the results of the proposed
inspections. The agency has no way of determining the number of
helicopters that might need these on-condition actions:
On-Condition Costs
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Action Labor cost Parts cost Cost per product
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Collect particles and perform 6 work-hours x $85 per $0..................... $510.
metallurgical analysis. hour = $510.
Close monitoring..................... 2 work-hours x $85 per $0..................... $170 per close
hour = $170. monitoring cycle.
Perform visual borescope inspection 1 work-hour x $85 per $0..................... $85.
of MGB bevel wheel. hour = $85.
Replace epicyclic module............. 56 work-hours x $85 per $50,524 (overhauled)... $55,284 per module.
hour = $4,760.
[[Page 53241]]
Replace bevel reduction module....... 56 work-hours x $85 per $18,500 (overhauled)... $23,260 per module.
hour = $4,760.
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Certain corrective action could vary significantly from helicopter
to helicopter. The FAA has no data to determine the costs to accomplish
the corrective action.
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 that the 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:
0
a. Removing Airworthiness Directive 2025-06-04, Amendment 39-22992 (90
FR 14723, April 4, 2025); and
0
b. Adding the following new airworthiness directive:
Airbus Helicopters: Docket No. FAA-2025-5032; Project Identifier AD-
2025-01042-R.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by January 9, 2026.
(b) Affected ADs
This AD replaces AD 2025-06-04, Amendment 39-22992 (90 FR 14723,
April 4, 2025) (AD 2025-06-04).
(c) Applicability
This AD applies to all Airbus Helicopters Model AS350B, AS350B1,
AS350B2, AS350B3, AS350BA, AS350D, AS355E, AS355F, AS355F1, AS355F2,
AS355N, AS355NP, EC130B4, and EC130T2 helicopters, certificated in
any category.
(d) Subject
Joint Aircraft System Component (JASC) Code 6320, Main Rotor
Gearbox.
(e) Unsafe Condition
This AD was prompted by an assessment performed by the
manufacturer which determined that additional maintenance actions
are necessary to improve detection of particles in the main gearbox
(MGB) with certain part-numbered planet gear bearings installed. The
FAA is issuing this AD to detect and correct particles in the MGB.
The unsafe condition, if not addressed, could result in reduced or
loss of control of the helicopter.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
Except as specified in paragraphs (h) and (i) of this AD: Comply
with all required actions and compliance times specified in, and in
accordance with, European Union Aviation Safety Agency AD 2023-0044,
dated February 28, 2023 (EASA AD 2023-0044).
(h) Exceptions to EASA AD 2023-0044
(1) Where EASA AD 2023-0044 defines ``serviceable MGB'' as ``An
affected MGB which has accumulated less than 330 flight hours (FH)
since new (first installation on a helicopter), or since an
overhaul, or since an inspection in accordance with the instructions
of the ASB'', this AD requires replacing that text with ``An
affected MGB which has accumulated less than 330 total hours time-
in-service (TIS) since new (zero total hours TIS), since last
overhaul if an overhaul has been accomplished, or since last
inspection and any specified corrective action in accordance with
the instructions of the ASB if an inspection and any specified
corrective action by following the instructions of the ASB have been
accomplished''.
(2) Where EASA AD 2023-0044 requires compliance in terms of
flight hours, this AD requires using TIS.
(3) Where EASA AD 2023-0044 refers to its effective date, this
AD requires using May 9, 2025 (the effective date of AD 2025-06-04).
(4) Where Note 1 in the material referenced in paragraph (1) of
EASA AD 2023-0044 specifies the option of 1 mechanical technician
and 1 crew member, for this AD, the pilot is only permitted to turn
the tail rotor (b). The owner/operator (pilot) holding at least a
private pilot certificate may turn the tail rotor (b) and must enter
compliance with paragraph (g) of this AD in the helicopter
maintenance records in accordance with 14 CFR 43.9(a) and
91.417(a)(2)(v). The record must be maintained as required by 14 CFR
91.417, 121.380, or 135.43. All other actions specified in Note 1 in
the material referenced in paragraph (1) of EASA AD 2023-0044 must
be accomplished by persons authorized under 14 CFR 43.3.
(5) Where Note 2 in the material referenced in paragraph (1) of
EASA AD 2023-0044 specifies contacting Airbus Helicopters [AH] for
further instructions if the bottom of the radius (a6) of the bevel
wheel (a3) or head screws (a4) (see Figure 2) are not clearly
visible, this AD requires, before further flight, accomplishing
action in accordance with a method approved by the FAA, EASA, or
Airbus Helicopters' EASA Design Organization Approval (DOA). If
approved by the DOA, the approval must include the DOA-authorized
signature.
(6) Instead of complying with paragraph (2) of EASA AD 2023-
0044, comply with the actions required by paragraphs (h)(6)(i) and
(ii) of this AD.
[[Page 53242]]
(i) After May 9, 2025 (the effective date of AD 2025-06-04), and
within the compliance time intervals specified in table 1 to
paragraph (h)(6)(i) of this AD, visually inspect the MGB magnetic
plug for particles.
Note 1 to paragraph (h)(6)(i): Aircraft Maintenance Manual (AMM)
task 60-00-00, 6-2A, or AMM task 60-00-00, 6-2, or Work Card 60-00-
00-602, as applicable, provides information regarding inspecting the
MGB magnetic plug.
Table 1 to paragraph (h)(6)(i)--MGB Magnetic Plug Inspections
----------------------------------------------------------------------------------------------------------------
Initial compliance times
(after May 9, 2025, the Interval compliance times
Helicopter model(s) effective date of AD 2025- (thereafter) (hours TIS)
06-04) (hours TIS)
----------------------------------------------------------------------------------------------------------------
AS350B, AS350B1, AS350BA, and AS350D...................... 5 100
AS355E, AS355F, AS355F1, AS355F2, AS355N, and AS355NP..... 5 100
AS350B2 and AS350B3....................................... 10 100
EC130B4................................................... 5 100
EC130T2................................................... 5 150
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(ii) If there is any particle as a result of any MGB magnetic
plug inspection required by paragraph (h)(6)(i) of this AD, before
further flight, borescope inspect the bevel wheel of the affected
MGB for particles as required by paragraph (1) of EASA AD 2023-0044.
If there is any particle as a result of the borescope inspection of
the bevel wheel, before further flight, collect and analyze the
particles as required by paragraph (3) of EASA AD 2023-0044.
(7) Where paragraph (3) of EASA AD 2023-0044 specifies ``If,
during any inspection as required by paragraph (1) or (2) of this
AD'', this AD requires replacing that text with ``If, during any
inspection as required by paragraph (1) of this AD''.
(8) Where the material referenced in paragraph (3) of EASA AD
2023-0044 specifies performing a metallurgical analysis and
contacting Airbus Helicopters if collected particles cannot be
characterized with Work Card 20-08-01-601, this AD does not require
contacting Airbus Helicopter but does require performing the
metallurgical analysis.
(9) Where the material referenced in paragraph (3) of EASA AD
2023-0044 contains a special flight permit provision, this AD does
not allow that provision but instead requires the special flight
permit limitations in paragraph (j) of this AD.
(10) Where the material referenced in paragraph (3) of EASA AD
2023-0044 specifies contacting Airbus Helicopters if the damaged
module cannot be identified, this AD requires, before further
flight, accomplishing action in accordance with a method approved by
the FAA, EASA, or Airbus Helicopters' EASA DOA. If approved by the
DOA, the approval must include the DOA-authorized signature.
(11) Where paragraph (5) of EASA AD 2023-0044 states ``to
contact AH for corrective action(s) instructions, and within the
compliance time specified therein, to accomplish those instructions
accordingly'', this AD requires replacing that text with
``accomplishing corrective actions in accordance with a method
approved by the FAA, EASA, or Airbus Helicopters' EASA DOA. If
approved by the DOA, the approval must include the DOA-authorized
signature''.
(12) Where paragraph (7) of EASA AD 2023-0044 states ``since new
(first installation a helicopter), or since an overhaul, or since an
inspection in accordance with the instructions of the ASB, as
applicable, and, thereafter, as required by this AD'', this AD
requires replacing that text with ``since new (zero total hours
time-in-service), or since last overhaul if an overhaul has been
accomplished, or since last inspection and any specified corrective
action in accordance with the instructions of the ASB if an
inspection and any specified corrective action by following the
instructions of the ASB have been accomplished, and thereafter as
required by this AD''.
(13) This AD does not adopt the ``Remarks'' section of EASA AD
2023-0044.
(i) No Reporting Requirement
Although the material referenced in EASA AD 2023-0044 specifies
to submit certain information to the manufacturer, this AD does not
require that action.
(j) Special Flight Permit
A special flight permit may be issued in accordance with 14 CFR
21.197 and 21.199 to permit a one-time, non-revenue flight to a
location where the actions required by this AD can be accomplished.
This flight must be performed with only essential flight crew.
(k) Alternative Methods of Compliance (AMOCs)
(1) The Manager, International Validation 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 International Validation Branch, send
it to the attention of the person identified in paragraph (l) 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.
(l) Additional Information
For more information about this AD, contact Dan McCully,
Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590; phone: (404) 474-5548; email:
[email protected].
(m) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference of the material listed in this paragraph
under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this material as applicable to do the actions
required by this AD, unless the AD specifies otherwise.
(3) The following material was approved for IBR on May 9, 2025
(90 FR 14723; April 4, 2025).
(i) European Union Aviation Safety Agency (EASA) AD 2023-0044,
dated February 28, 2023.
(ii) [Reserved]
(4) For EASA material identified in this AD, contact EASA,
Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; phone: +49 221 8999
000; email: [email protected]; website: easa.europa.eu. You may
find the EASA material on the EASA website at ad.easa.europa.eu.
(5) You may view this material at the FAA, Office of the
Regional Counsel, Southwest Region, 10101 Hillwood Parkway, Room 6N-
321, Fort Worth, TX 76177. For information on the availability of
this material at the FAA, call (817) 222-5110.
(6) You may view this material at the National Archives and
Records Administration (NARA). For information on the availability
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].
Issued on November 20, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft
Certification Service.
[FR Doc. 2025-20852 Filed 11-24-25; 8:45 am]
BILLING CODE 4910-13-P