Proposed Rule2025-19083
Airworthiness Directives; Airbus Helicopters
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
September 30, 2025
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA proposes to adopt a new airworthiness directive (AD) for all Airbus Helicopters Model AS355E, AS 355-F, AS 355-F1, AS355F2, and AS355N helicopters. This proposed AD was prompted by reports of cracks in the legs of the side supports of the tail rotor transmission fan. This proposed AD would require repetitively inspecting the side supports of the tail rotor transmission fan for cracks and, depending on the results, replacing both side supports. The FAA is proposing this AD to address the unsafe condition on these products.
Full Text
<html>
<head>
<title>Federal Register, Volume 90 Issue 187 (Tuesday, September 30, 2025)</title>
</head>
<body><pre>
[Federal Register Volume 90, Number 187 (Tuesday, September 30, 2025)]
[Proposed Rules]
[Pages 46773-46776]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-19083]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-3420; Project Identifier MCAI-2025-00225-R]
RIN 2120-AA64
Airworthiness Directives; Airbus Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for all Airbus Helicopters Model AS355E, AS 355-F, AS 355-F1, AS355F2,
and AS355N helicopters. This proposed AD was prompted by reports of
cracks in the legs of the side supports of the tail rotor transmission
fan. This proposed AD would require repetitively inspecting the side
supports of the tail rotor transmission fan for cracks and, depending
on the results, replacing both side supports. The FAA is proposing this
AD to address the unsafe condition on these products.
DATES: The FAA must receive comments on this NPRM by November 14, 2025.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
<bullet> Federal eRulemaking Portal: Go to <a href="http://regulations.gov">regulations.gov</a>. Follow
the instructions for submitting comments.
<bullet> Fax: (202) 493-2251.
<bullet> 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.
<bullet> 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 <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2025-3420; 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:
<bullet> 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:
<a href="/cdn-cgi/l/email-protection#7c3d380f3c191d0f1d5219090e130c1d521909"><span class="__cf_email__" data-cfemail="4c0d083f0c292d3f2d6229393e233c2d622939">[email protected]</span></a>; website: easa.europa.eu. You may find this material
on the EASA website at ad.easa.europa.eu.
<bullet> 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. It is also available at
<a href="http://regulations.gov">regulations.gov</a> under Docket No. FAA-2025-3420.
FOR FURTHER INFORMATION CONTACT: Kim-Anh Tran, Aviation Safety
Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
phone:
[[Page 46774]]
(316) 946-4190; email: <a href="/cdn-cgi/l/email-protection#a7ccceca8ac6c9cf89d389d3d5c6c9e7c1c6c689c0c8d1"><span class="__cf_email__" data-cfemail="22494b4f0f434c4a0c560c5650434c624443430c454d54">[email protected]</span></a>.
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-2025-3420;
Project Identifier MCAI-2025-00225-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 amend 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
<a href="http://regulations.gov">regulations.gov</a>, 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 Kim-
Anh Tran, 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
EASA, which is the Technical Agent for the Member States of the
European Union, has issued EASA AD 2025-0052, dated February 28, 2025
(EASA AD 2025-0052) (also referred to as the MCAI), to correct an
unsafe condition on all Airbus Helicopters Model AS 355 E, AS 355 F, AS
355 F1, AS 355 F2, and AS 355 N helicopters. The MCAI states there have
been reports, following scheduled maintenance, of cracks in the legs of
the left hand (LH) and right hand (RH) side supports of the tail rotor
transmission fan installed on helicopters with the post-mod 07-9062
configuration. This condition, if not addressed, could result in
failure of the legs supporting the tail rotor transmission fan and
displacement of the tail rotor transmission fan assembly, which could
lead to the loss of the engine and main gearbox cooling function, loss
of the tail rotor drive, and consequent loss of control of the
helicopter.
The FAA is issuing this AD to detect and correct a cracked side
support of the tail rotor transmission fan.
You may examine the MCAI in the AD docket at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2025-3420.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed EASA AD 2025-0052, which specifies procedures for
repetitive inspections of the LH and RH side supports of the tail rotor
transmission fan, having part number (P/N) 355A34104006 (LH) and P/N
355A34104106 (RH) respectively, for cracks and, if any crack is found
on any side support, replacement of both side supports. EASA AD 2025-
0052 also specifies reporting the inspection results to the
manufacturer. 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.
FAA's Determination
These products have been approved by the civil aviation authority
(CAA) of another country and are approved for operation in the United
States. Pursuant to the FAA's bilateral agreement with this State of
Design Authority, that authority has notified the FAA of the unsafe
condition described in the MCAI referenced above. 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 accomplishing the actions specified
in EASA AD 2025-0052, 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 requires reporting inspection results to the manufacturer,
whereas this proposed AD would not.
Interim Action
The FAA considers that this proposed AD would be an interim action.
The manufacturer is still investigating the root cause of the unsafe
condition identified in this AD. If final action is later identified,
the FAA might consider further rulemaking.
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 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 incorporates EASA AD 2025-
0052 by reference in the FAA final rule. This proposed AD would,
therefore, require compliance with EASA AD 2025-0052 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 2025-0052 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 2025-0052. Material referenced in EASA AD 2025-
0052 for compliance will be available at <a href="http://regulations.gov">regulations.gov</a> under Docket
No. FAA-2025-3420 after the FAA final rule is published.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 38 helicopters of U.S. registry. The FAA estimates the following
costs to comply with this proposed AD:
[[Page 46775]]
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators
----------------------------------------------------------------------------------------------------------------
Inspect both side supports............ 1.5 work-hours x $85 per $0 $128 $4,864
hour = $128.
----------------------------------------------------------------------------------------------------------------
The FAA estimates the following costs to do any necessary on-
condition actions that would be required based on the results of the
proposed inspection. The agency has no way of determining the number of
helicopters that might need these on-condition actions:
On-Condition Costs
----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product
----------------------------------------------------------------------------------------------------------------
Replace both side supports.................... 24 work-hours x $85 per hour = $600 $2,640
$2,040.
----------------------------------------------------------------------------------------------------------------
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
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:
Airbus Helicopters: Docket No. FAA-2025-3420; Project Identifier
MCAI-2025-00225-R.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by November 14, 2025.
(b) Affected ADs
None.
(c) Applicability
This AD applies to Airbus Helicopters Model AS355E, AS 355-F, AS
355-F1, AS355F2, and AS355N helicopters, certificated in any
category.
(d) Subject
Joint Aircraft System Component (JASC) Code 6500, Tail Rotor
Drive System.
(e) Unsafe Condition
This AD was prompted by reports of cracks in the legs of the
side support of the tail rotor transmission fan. The FAA is issuing
this AD to detect and correct a cracked side support of the tail
rotor transmission fan. The unsafe condition, if not addressed,
could result in failure of the legs supporting the tail rotor
transmission fan and displacement of the tail rotor transmission fan
assembly, which could lead to the failure of the engine and main
gearbox cooling function, loss of the tail rotor drive, and
consequent loss of control of the helicopter.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Requirements
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 2025-0052,
dated February 28, 2025 (EASA AD 2025-0052).
(h) Exceptions to EASA AD 2025-0052
(1) Where EASA AD 2025-0052 requires compliance in terms of
flight hours, this AD requires using hours time-in-service.
(2) Where EASA AD 2025-0052 refers to its effective date, this
AD requires using the effective date of this AD.
(3) Where paragraph (2) of EASA AD 2025-0052 specifies ``replace
both affected parts in accordance with the instructions of the
ASB'', this AD requires replacing that text with ``remove both
affected parts from service and replace with new (zero hours time-
in-service) parts in accordance with the instructions of the ASB''.
(4) This AD does not adopt the ``Remarks'' section of EASA AD
2025-0052.
(i) No Reporting Requirement
Although EASA AD 2025-0052 and the material referenced in EASA
AD 2025-0052 specify to submit certain information to the
manufacturer, this AD does not include that requirement.
(j) Special Flight Permits
Special flight permits are prohibited.
(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
[[Page 46776]]
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: <a href="/cdn-cgi/l/email-protection#c3828e8c8083a5a2a2eda4acb5"><span class="__cf_email__" data-cfemail="4a0b0705090a2c2b2b642d253c">[email protected]</span></a>.
(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 Kim-Anh Tran,
Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590; phone: (316) 946-4190; email: <a href="/cdn-cgi/l/email-protection#b0dbd9dd9dd1ded89ec49ec4c2d1def0d6d1d19ed7dfc6"><span class="__cf_email__" data-cfemail="52393b3f7f333c3a7c267c2620333c123433337c353d24">[email protected]</span></a>.
(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.
(i) European Union Aviation Safety Agency (EASA) AD 2025-0052,
dated February 28, 2025.
(ii) [Reserved]
(3) For EASA material identified in this AD, contact EASA,
Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; phone: +49 221 8999
000; email: <a href="/cdn-cgi/l/email-protection#e6a7a295a683879587c8839394899687c88393"><span class="__cf_email__" data-cfemail="2061645360454153410e4555524f50410e4555">[email protected]</span></a>; website: easa.europa.eu. You may
find the EASA material on the EASA website at ad.easa.europa.eu.
(4) 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.
(5) You may view this material at the National Archives and
Records Administration (NARA). For information on the availability
of this material at NARA, visit <a href="http://www.archives.gov/federal-register/cfr/ibr-locations">www.archives.gov/federal-register/cfr/ibr-locations</a> or email <a href="/cdn-cgi/l/email-protection#b4d2c69adddac7c4d1d7c0dddbdaf4dad5c6d59ad3dbc2"><span class="__cf_email__" data-cfemail="3a5c48145354494a5f594e5355547a545b485b145d554c">[email protected]</span></a>.
Issued on September 26, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft
Certification Service.
[FR Doc. 2025-19083 Filed 9-29-25; 8:45 am]
BILLING CODE 4910-13-P
</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>Indexed from Federal Register on September 30, 2025.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.