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MCAI-2025-01763-R; Airbus Helicopters Model AS350B2 Helicopters; ATA 29 – Hydraulic Power – Single Generation Hydraulic System Wiring Diode – Cut-Off Test
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Published Document: 2026-16507 (91 FR 52221)
This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.
AGENCY:
Federal Aviation Administration (FAA), DOT.
ACTION:
Final rule.
SUMMARY:
The FAA is adopting a new airworthiness directive (AD) for certain Airbus Helicopters Model AS350B2 helicopters. This AD was prompted by a report of magnetization on the solenoid valves for the three main servo-controls, the regulator block, and the tail servo-control due to a diode not properly installed in the hydraulic circuit. This AD requires performing a cut-off test of the rear rotor actuator valve and, depending on the results of the test, performing corrective actions. The FAA is issuing this AD to address the unsafe condition on these products.
DATES:
This AD is effective September 17, 2026.
The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of September 17, 2026.
ADDRESSES:
AD Docket:
You may examine the AD docket at
regulations.gov
under Docket No. FAA-2026-4646; 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 final rule, the mandatory continuing airworthiness information (MCAI), any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
For European Union Aviation Safety Agency (EASA) material identified in this AD, contact Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; phone: +49 221 8999 000; email:ADs@easa.europa.eu;
website:
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. It is also available atregulations.gov
under Docket No. FAA-2026-4646.
FOR FURTHER INFORMATION CONTACT:
Aryanna Sanchez, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (817) 222-4058; email:
aryanna.t.sanchez@faa.gov.
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Airbus Helicopters Model AS350B2 helicopters. The NPRM was published in the
Federal Register
on May 28, 2026 (91 FR 31673). The NPRM was prompted by an MCAI, issued by EASA, which is the Technical Agent for the Member States of the European Union. EASA issued EASA AD 2025-0263, dated November 26, 2025; corrected December 9, 2025 (EASA AD 2025-0263) (also referred to as the MCAI). The MCAI states that during maintenance on a helicopter, magnetization was observed on the solenoid valves for the three main servo-controls, the regulator block, and the tail servo-control. The MCAI also states that after further investigation, it was determined that diode 43D2 was not installed in the hydraulic circuit. In the NPRM, the FAA proposed to require performing a cut-off test of the rear rotor actuator valve and depending on the results of the test, the FAA proposed to require performing corrective actions. The FAA is issuing this AD to address the unsafe condition on these products.
You may examine the MCAI in the AD docket at
regulations.gov
under Docket No. FAA-2026-4646.
Discussion of Final Airworthiness Directive
Comments
The FAA received no comments on the NPRM or on the determination of the costs.
Conclusion
These products have been approved by the civil 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, that authority has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed EASA AD 2025-0263, which specifies procedures for performing a cut-off test, and, if any discrepancy (failure of the test) is detected, replacing any affected diodes, or installing any missing diodes. This material is reasonably available because the interested parties have access to it through their normal course of business
( printed page 52222)
or by the means identified in the
ADDRESSES
section.
Costs of Compliance
The FAA estimates that this AD affects 12 helicopters of U.S. registry.
The FAA estimates the following costs to comply with this AD:
Estimated Costs
Action
Labor cost
Parts cost
Cost per
product
Cost on U.S.
operators
Perform cut-off test
3 work-hours × $85 per hour = $255
$0
$255
$3,060
The FAA estimates the following costs to do any installations or replacements that would be required based on the results of the test. The agency has no way of determining the number of helicopters that might need these installations or replacements.
On-Condition Costs
Action
Labor cost
Parts cost
Cost per
product
Replace diode
1 work-hour × $85 per hour = $85
$180
$265
Install diode
5 work-hours × $85 per hour = $425
1,000
1,425
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
This AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD:
(2) Will not affect intrastate aviation in Alaska, and
(3) Will 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 airworthiness directive (AD) is effective September 17, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all Airbus Helicopters Model AS350B2 helicopters as specified in European Union Aviation Safety Agency AD 2025-0263, dated November 26, 2025; corrected December 9, 2025 (EASA AD 2025-0263).
(d) Subject
Joint Aircraft System Component (JASC) Code 2900, Hydraulic power system.
(e) Unsafe Condition
This AD was prompted by a report of magnetization on the solenoid valves for the three main servo-controls, the regulator block, and the tail servo-control due to a diode not properly installed in the hydraulic circuit. The FAA is issuing this AD to prevent loss of the efficiency of the yaw load compensator and of hydraulic assistance for the three main servo-controls and the tail servo-control. The unsafe condition, if not addressed, could result in reduced 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, EASA AD 2025-0263.
(h) Exceptions to EASA AD 2025-0263
(1) Where EASA AD 2025-0263 refers to its effective date, this AD requires using the effective date of this AD.
(2) Where EASA AD 2025-0263 requires compliance in terms of flight hours, this AD requires using hours' time-in-service.
(3) Where the material referenced in EASA AD 2025-0263 specifies “remove the diode 43D2”, this AD requires replacing that text with “remove the diode 43D2 from service”.
(4) This AD does not adopt the “Remarks” section of EASA AD 2025-0263.
(i) No Reporting Requirement
Although the material referenced in EASA AD 2025-0263 specifies to submit certain information to the manufacturer, this AD does not require that action.
( printed page 52223)
(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 Aryanna Sanchez, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (817) 222-5110; email:
aryanna.t.sanchez@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.
(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 2025-0263, dated November 26, 2025; corrected December 9, 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:
ADs@easa.europa.eu;
website:
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.