The FAA proposes to adopt a new airworthiness directive (AD) for all Airbus Helicopters Model AS355E, AS355F, AS355F1, AS355F2, and AS355N helicopters. This proposed AD was prom...
The FAA proposes to adopt a new airworthiness directive (AD) for all Airbus Helicopters Model AS355E, AS355F, AS355F1, AS355F2, and AS355N helicopters. This proposed AD was prompted by the determination that the tail rotor drive fan wheels (fan wheels) and the impeller second stage have been incorrectly identified during production. This proposed AD would require verifying the serial number and amendment of the log cards of the affected parts, and depending on the findings, performing a one-time borescope inspection to verify consistency between the log cards and the affected parts. Depending on the inspection results, this proposed AD would require replacing or re-identifying certain parts. This proposed AD would also prohibit the installation of certain fan wheels and impeller second stages on any helicopter. The FAA is proposing this AD to address the unsafe condition on these products.
DATES:
The FAA must receive comments on this NPRM by August 3, 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-2026-4657; 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:ADs@easa.europa.eu;
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, Airworthiness Products Section, Operational Safety Branch, 10101 Hillwood Parkway, Fort Worth, TX 76177. For information on the availability of this material at the FAA, call (817) 222-5110.
FOR FURTHER INFORMATION CONTACT:
Andrew Gronau, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (847) 294-7378; email:
andrew.s.gronau@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 using a method listed under
ADDRESSES
. Include “Docket No. FAA-2026-4657; Project Identifier MCAI-2024-00383-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.
( printed page 36772)
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 Andrew Gronau, 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, issued EASA AD 2024-0127, dated July 3, 2024 (EASA AD 2024-0127) (also referred to as the MCAI), to correct an unsafe condition on Airbus Helicopters Model AS 355 E, AS 355 F, AS 355 F1, AS 355 F2, and AS 355 N helicopters. The MCAI states that it was determined that the fan wheel part number (P/N) 704A33691014 amdt [amendment] C and the impeller second stage P/N 704A33691015 amdt C have been incorrectly identified in production. Incorrect identification may cause the loss of traceability of the affected parts, which could lead to required inspections not being accomplished. The unsafe condition, if not addressed, could lead to undetected fatigue failure of the affected parts and result in loss of control of the helicopter.
You may examine the MCAI in the AD docket at
regulations.gov
under Docket No. FAA-2026-4657.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed EASA AD 2024-0127, which specifies procedures for verifying the helicopter's existing log card to determine whether an affected fan wheel and impeller second stage are installed. Depending on the results, EASA AD 2024-0127 specifies procedures for performing a borescope inspection of the affected parts for further verification and either replacing affected parts or reidentifying the parts and amending their log cards. EASA AD 2024-0127 also prohibits installing an affected fan wheel or impeller second stage 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 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 2024-0127, described previously, as incorporated by reference, except for any differences identified as exceptions in the regulatory text of this AD.
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 proposes to incorporate EASA AD 2024-0127 by reference in this FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 2024-0127 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 2024-0127 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 2025-0127. Material required by EASA AD 2024-0127 for compliance will be available at
regulations.gov
under Docket No. FAA-2026-4657 after the FAA final rule is published.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would affect four helicopters of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:
Estimated Costs
Action
Labor cost
Parts cost
Cost per
product
Cost on U.S. operators
Review log card
1 work-hour × $85 per hour = $85
$0
$85
$340
The FAA estimates the following costs to do any replacements 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 replacements:
( printed page 36773)
On-Condition Costs
Action
Labor cost
Parts cost
Cost per
product
Perform borescope inspection of the fan wheel
1 work-hour × $85 per hour = $85
0
85
Perform borescope inspection of the impeller second stage
1 work-hour × $85 per hour = $85
0
85
Replace fan wheel
2 work-hours × $85 per hour = $170
1,534
1,703
Replace impeller second stage
2 work-hours × $85 per hour = $170
1,219
1,389
Perform balance of tail rotor drive shaft
2 work-hours × $85 per hour = $170
0
170
Re-identify the fan wheel or the impeller second stage
1 work-hour × $85 per hour = $85
0
85
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:
(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.
This AD was prompted by the determination that the tail rotor drive fan wheel and impeller second stage have been incorrectly identified during production. The FAA is issuing this AD to detect and address incorrect identification of the affected parts. The unsafe condition, if not addressed, may cause the loss of traceability of the affected parts, which could lead to undetected fatigue failure of the affected parts and 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 2024-0127, dated July 3, 2024 (EASA AD 2024-0127).
(h) Exceptions to EASA AD 2024-0127
(1) Where EASA AD 2024-0127 refers to its effective date, this AD requires using the effective date of this AD.
(2) Where EASA AD 2024-0127 requires compliance in terms of flight hours, this AD requires using hours time-in-service.
(3) Where EASA AD 2024-0127 defines “affected part”, this AD requires replacing that text with “tail rotor drive fan wheel having part number (P/N) 704A33691014 amdt [amendment] C and impeller second stage P/N 704A33691015 amdt [amendment] C, and a serial number (S/N), as identified in the Log Card, listed as `S/N affected' in section 4.5 or 4.6 of the accomplishment procedure of Airbus Helicopters Alert Service Bulletin ASB AS355-65-00-0001, Issue 001 dated May 27, 2024”.
(4) This AD does not adopt the “Remarks” section of EASA AD 2024-0127.
(i) No Reporting Requirement
Although the material referenced in EASA AD 2024-0127 specifies to submit certain information to the manufacturer, this AD does not require that action.
(j) 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 (k) of this AD and email to:
AMOC@faa.gov.
(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.
(k) Additional Information
For more information about this AD, contact Andrew Gronau, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (847) 294-7378; email:
andrew.s.gronau@faa.gov.
(l) 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.
( printed page 36774)
(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 2024-0127, dated July 3, 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:
ADs@easa.europa.eu;
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, Airworthiness Products Section, Operational Safety Branch, 10101 Hillwood Parkway, Fort Worth, TX 76177. For information on the availability of this material at the FAA, call (817) 222-5110.