# [Amended]
**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, AS355N, and AS355NP helicopters. This proposed AD was prompted by a report of a structural crack in the vertical attachment spar of the tail fin. This proposed AD would require repetitive inspections of certain vertical upper fin spars and, depending on the results, corrective action. This proposed AD would also prohibit installing certain upper fin assemblies. The FAA is proposing this AD to address the unsafe condition on these products.
**DATES:**
The FAA must receive comments on this NPRM by February 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:
• *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-2025-5039; 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 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.*
• 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:**
Yves Petiote, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (202) 975-4867; 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-2025-5039; Project Identifier MCAI-2024-00426-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 *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 Yves Petiote, 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 a series of ADs, the most recent being EASA AD 2023-0154R1, dated July 19, 2024 (EASA AD 2023-0154R1) (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, AS355 F2, AS355 N, and AS 355 NP helicopters. The MCAI advises of a report of a structural crack (not a complete failure) in the vertical attachment spar of the tail fin.
The MCAI states that the unsafe condition, if not addressed, may lead to in-flight separation of the upper part of the vertical fin, which could result in loss of control of the helicopter. The FAA is proposing this AD to address the unsafe condition on these products.
EASA has issued related EASA AD 2024-0139, dated July 12, 2024 (EASA AD 2024-0139), for these same model helicopters as well as certain Model AS350B3 helicopters, to address cracking in a different area of the upper fin spar as well as the fin's front attachment screws. The FAA issued AD 2025-24-04, Amendment 39-23199 (90 FR 56679, December 8, 2025) (AD 2025-24-04), to address EASA AD 2024-0139. This proposed AD includes actions that would be contingent on some of the required actions in AD 2025-24-04.
You may examine the MCAI in the AD docket at *regulations.gov* under Docket No. FAA-2025-5039.
**Material Incorporated by Reference Under 1 CFR Part 51**
FAA reviewed EASA AD 2023-0154R1, which specifies procedures for removing the tail gear box (TGB) fairing and the rear fairing from the tail boom, cleaning, and inspecting the right-hand external side around the two top screws of certain upper fin spars for a crack. EASA AD 2023-0154R1 also specifies procedures for conducting repetitive borescope inspections of that upper fin spar area for a crack or repeating the initial inspection as an alternative. Additionally, EASA AD 2023-0154R1 specifies accomplishing the inspections prior to and after maintenance flights that exceed the reduced V <sub>NE</sub> (Velocity Never Exceed) required by EASA AD 2024-0139 and after each other flight that exceeds the reduced V <sub>NE</sub> required by EASA AD 2024-0139. Depending on the results of an inspection, EASA AD 2023-0154R1 specifies procedures for marking the two top right-hand screw ends or replacing the upper fin. EASA AD 2023-0154R1 further specifies that installing an upper fin assembly part number (P/N) 355A14-0522-1751 constitutes terminating action for its repetitive inspection requirements and prohibits installing certain upper fin assemblies on any helicopter. 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 aviation authority 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, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA is proposing this AD after evaluating all known relevant information and 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 2023-0154R1, 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 AD and the MCAI” for a discussion of these differences.
**Differences Between This Proposed AD and the MCAI**
Where the MCAI defines an affected part as those listed in any revision of the manufacturer's service information, this proposed AD would define an affected part as those listed in specific versions of the manufacturer's service information and would include upper fin assemblies for which the P/N cannot be determined.
**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 2023-0154R1 by reference in the FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 2023-0154R1 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 2023-0154R1 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 2023-0154R1. Material referenced in EASA AD 2023-0154R1 for compliance will be available at *regulations.gov* under Docket No. FAA-2025-5039 after the FAA final rule is published.
**Costs of Compliance**
The FAA estimates that this AD, if adopted as proposed, would affect 177 helicopters of U.S. registry. Labor rates are estimated at $85 per hour. Based on these numbers, the FAA estimates the following costs to comply with this proposed AD.
Initial cleaning and inspection of the vertical fin spar and, if necessary, application of a paint mark on the top two right-hand screw ends would take 2.5 work-hours for an estimated cost of $213 per helicopter and $37,701 for the U.S. fleet.
Repetitive borescope inspection of the upper fin spar would take 0.5 work-hour for an estimated cost of $43 per helicopter and up to $7,611 for the U.S. fleet, per inspection cycle. Alternatively, repeating the initial inspection would take 2.5 work-hours for an estimated cost of $213 per helicopter and up to $37,701 for the U.S. fleet, per inspection cycle.
If required, removing the upper fin from service and installing upper fin assembly P/N 355A14-0522-1751 to modify the upper fin would take 40 work-hours and parts would cost $25,360 for an estimated cost of $28,760 per helicopter.
The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some of the costs of this proposed AD may be covered under warranty, thereby reducing the cost impact on affected operators.
**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.
§ 39.13
2. The FAA amends § 39.13 by adding the following new airworthiness directive:
*Airbus Helicopters:* Docket No. FAA-2025-5039; Project Identifier MCAI-2024-00426-R.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by February 2, 2026.
**(b) Affected ADs**
This AD affects AD 2025-24-04, Amendment 39-23199 (90 FR 56679, December 8, 2025) (AD 2025-24-04).
**(c) Applicability**
This AD applies to Airbus Helicopters Model AS355E, AS 355-F, AS 355-F1, AS355F2, AS355N, and AS355NP helicopters, certificated in any category.
**(d) Subject**
Joint Aircraft System Component (JASC) Code 5531, Vertical Stabilizer, Spar/Rib Structure.
**(e) Unsafe Condition**
This AD was prompted by a report of a structural crack in the vertical attachment spar of the tail fin. The FAA is issuing this AD to address cracking in the upper fin spar. This condition could lead to in-flight separation of the upper part of the vertical fin, which could result in 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 2023-0154R1, dated July 19, 2024 (EASA AD 2023-0154R1).
**(h) Exceptions to EASA AD 2023-0154R1**
(1) Where EASA AD 2023-0154R1 defines an “affected part,” this AD requires replacing that text with “an upper fin assembly having a part number (P/N) identified in the Applicability, Accomplishment Procedure, of Airbus Helicopters Emergency Alert Service Bulletin EASB AS355-05-00-0001, Issue 001, dated July 25, 2023, or Issue 002, dated July 9, 2024, or an upper fin assembly having a P/N that cannot be determined.
*Note 1 to paragraph (h)(1):* MOD 0720098 involves installing a new upper fin that has a reinforced fin spar (P/N 355A14-0522-1751) that is not affected by this AD. Airbus Helicopters Alert Service Bulletin No. AS355-55.00.18, Revision 1, dated June 6, 2024, contains information regarding MOD 0720098.
(2) Where EASA AD 2023-0154R1 refers to August 3, 2023 (the effective date of EASA AD 2023-0154, dated July 27, 2023), this AD requires using the effective date of this AD.
(3) Where EASA AD 2023-0154R1 requires compliance in terms of flight hours, this AD requires using hours time-in-service.
(4) Where paragraph (3) of EASA AD 2023-0154R1 specifies “following the Rotorcraft Flight Manual (RFM) amendment as required by paragraph (1) or (2) of EASA AD 2024-0139, as applicable, it is allowed to exceed the temporary reduced Vne during a maintenance flight”, this AD requires replacing that text with “following the Rotorcraft Flight Manual (RFM) amendment required by AD 2025-24-04, it is allowed to exceed the temporary reduced V <sub>NE</sub> during a flight to perform an operational check as specified in 14 CFR 91.407”.
(5) Where paragraphs (3.1), (3.2), and (3.3) of EASA AD 2023-0154R1 specify “maintenance flight”, this AD requires replacing that text with “flight to perform an operational check as specified in 14 CFR 91.407”.
(6) Where paragraph (4) of EASA AD 2023-0154R1 specifies “if, following the RFM amendment as required by paragraph (1) or (2) of EASA AD 2024-0139, as applicable, the temporary reduced Vne is exceeded on a helicopter”, this AD requires replacing that text with “if, following the RFM amendment required by AD 2025-24-04, the temporary reduced V <sub>NE</sub> is exceeded on a helicopter”.
(7) Where Note 1 of EASA AD 2023-0154R1 specifies “It is allowed to temporarily remove the RFM amendment and the placard, as required by paragraph (1) or (2) of EASA AD 2024-0139, as applicable, to allow maintenance flight(s) during which the temporarily reduced Vne may be exceeded”, this AD requires replacing that text with “It is allowed to temporarily remove the RFM amendment and the placard required by AD 2025-24-04 to allow flight(s) to perform an operational check as specified in 14 CFR 91.407, during which the temporarily reduced V <sub>NE</sub> may be exceeded”.
*Note 2 to paragraph (h)(7):* Refer to AD 2025-24-04 for requirements pertaining to exceeding V <sub>NE</sub> 110 kts. Airbus Helicopters Emergency Alert Service Bulletin EASB AS355-05-00-0001, Issue 002, dated July 9, 2024, also contains information regarding exceeding Vne 110 kts.
(8) Instead of complying with paragraph (6) of EASA AD 2023-0154R1, if there is a crack as a result of the inspections required by paragraphs (1) through (4) of EASA AD 2023-0154R1, this AD requires, before further flight, removing the upper fin from service and installing upper fin assembly P/N 355A14-0522-1751 in accordance with paragraph (7) and Note 2 of EASA AD 2023-0154R1.
(9) Where Note 2 of EASA AD 2023-0154R1 specifies “paragraph (12) of EASA AD 2024-0139”, this AD requires replacing that text with “AD 2025-24-04”.
(10) This AD does not adopt the “Remarks” section of EASA AD 2023-0154R1.
**(i) No Reporting Requirement**
Although the material referenced in EASA AD 2023-0154R1 specifies 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 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)(1) 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) Related Information**
(1) For more information about this AD, contact Yves Petiote, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (202) 975-4867; email: *[email protected]* .
(2) Airbus Helicopters material identified in this AD that is not incorporated by reference is available at the address specified in paragraph (m)(3) of this AD.
**(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 this AD specifies otherwise.
(i) European Union Aviation Safety Agency (EASA) AD 2023-0154R1, dated July 19, 2024.
(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: *[email protected]* ; 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 *www.archives.gov/federal-register/cfr/ibr-locations* or email *[email protected]* .
Issued on December 12, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.