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 Canada Limited Partnership Model BD-500-1A10 and BD-500-1A11 airplanes. The NPRM was published in the Federal Register on September 15, 2025 (90 FR 44356). The NPRM was prompted by AD CF-2024-37, dated November 4, 2024 (Transport Canada AD CF-2024-37) (also referred to as the MCAI), issued by Transport Canada, which is the aviation authority for Canada. The MCAI states that there have been several reports of fuel transfer float valves failing in the closed position, preventing normal fuel transfer between the center fuel tank and wing fuel tanks. An investigation determined that high friction of the fuel transfer float valve carbon seal prevents the fuel transfer float valve from opening. Each wing tank is equipped with one fuel transfer float valve. If one fuel transfer float valve fails closed, the crew is alerted and may manually transfer fuel to correct the resulting lateral fuel imbalance. A gravity fuel transfer system provides a back-up to the manual transfer. If both fuel transfer float valves simultaneously fail in the closed position, the crew is alerted, and fuel in the center tank becomes unusable as it cannot be transferred to the wing tanks. The crew may need to divert to prevent fuel starvation before reaching the destination airport. Simultaneous failure of both fuel transfer float valves in the closed position is critical for ETOPS missions as fuel starvation and engine shutdown may occur before reaching a diversion airport. In the NPRM, the FAA proposed to require replacing the existing fuel transfer float valves on airplanes approved for ETOPS, as specified in Transport Canada AD CF-2024-37. The FAA is issuing this AD to address the simultaneous failure of both fuel transfer float valves in the closed position during an ETOPS flight. The unsafe condition, if not addressed, during an ETOPS flight, could lead to a forced diversion or fuel starvation and engine shutdown before reaching a diversion airport. You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2025-2545. Discussion of Final Airworthiness Directive Comment The FAA received comments from the Citizens Rulemaking Alliance. The following presents the comments received on the NPRM and the FAA's response to each comment. Request To Justify Forgoing Notice and Comment or Issue an NPRM The commenter requested that the FAA either provide its justification for finding good cause to bypass notice and comment procedures, convert this action to an NPRM, or stay the effective date until 30 days after close of a comment period of at least 45 days. The commenter asserted the FAA has not adequately justified use of the good cause exemption to bypass notice and comment and the 30-day delayed effective date. The FAA notes the comment was submitted in response to an NPRM for which the FAA provided a 45-day comment period. This final rule is effective 35 days after its publication in the Federal Register . Therefore, no change to this AD is necessary. Request To Make Incorporation by Reference (IBR) Materials Reasonably Available The commenter stated that the FAA's current practices for IBR frequently fail to meet the legal and regulatory standards for reasonable availability. The commenter called on the FAA to guarantee that all IBR materials are easily and freely accessible to the public and affected parties for both commenting and compliance purposes. They also requested that this access be documented in the rulemaking record. The FAA's practices comply with 5 U.S.C. 552(a) of the Administrative Procedure Act and 1 CFR part 51. The FAA makes IBR materials available in the AD docket when the final rule is published in the Federal Register , following formal approval of the IBR by the Office of the Federal Register. Materials may only be posted before the final rule's publication if they are already publicly available or if there is written consent from the owner of the IBR material. All relevant materials incorporated by reference will be accessible in the AD docket on Regulations.gov , which the public can access without registration or fees. The FAA also provides summaries and access details in the preamble and regulatory text, makes materials available for inspection at FAA and National Archives and Records Administration (NARA) offices, offers publisher contact information, and obtains formal IBR approval from the Office of the Federal Register. These efforts are intended to ensure that all IBR materials meet the "reasonably available" standard required by 1 CFR part 51. The FAA did not change this AD as a result of this comment. Request To Comply With the Paperwork Reduction Act (PRA) The commenter requested that the FAA revise the AD to comply with the PRA if reporting is required or remove any reporting provisions until PRA requirements are satisfied. If reporting is not required, the commenter requested the FAA clarify that in the AD. The FAA notes this AD does not require reporting. If an AD were to require reporting, the preamble of the AD would include a paragraph titled "Paperwork Reduction Act" that would provide the applicable OMB control number, required PRA statements, and the estimated time to collect the required information (burden). Any costs associated with the reporting requirement would be included in the Costs of Compliance section in the preamble of the AD. Therefore, the FAA did not change this AD as a result of this comment. Request To Provide Additional Cost Information The commenter requested that the FAA add to the AD docket the methodology and assumptions supporting the estimated cost of the proposed AD and reopen the comment period for public input on the additional cost information. The commenter stated that the FAA should also provide the fleet size, per airplane labor and parts cost, any assumed downtime or out-of-service impacts, and any assumption that the manufacturer would provide parts free of charge. The FAA recognizes that, in doing the actions required by an AD, operators might incur indirect or incidental costs in addition to the direct costs. The cost analysis in an AD typically describes only the direct costs of the specific actions required by an AD, which does not include indirect or incidental costs such as downtime, loss of revenue, planning, or time necessitated by other administrative actions since those costs might vary significantly among operators. The number of work hours necessary to do the required actions of an AD is provided by the manufacturer. This number represents the time necessary to perform only the actions actually required by an AD. The cost of parts or special tools, if necessary, to complete the actions required by an AD is also provided by the manufacturer. Further, when the FAA is informed that the manufacturer may cover some or all of the estimated costs of an AD under warranty, the FAA indicates that in the AD. In the Cost of Compliance section of the proposed AD, the FAA disclosed the estimated number of work hours and the number of airplanes affected on the U.S. registry. The FAA did not disclose an estimated parts cost in the proposed AD but noted the parts would be provided at no charge to all operators for a limited time. Since the FAA has assessed and disclosed the total known costs of the AD requirements in the Costs of Compliance section of the proposed AD, and the commenter did not provide additional cost data for the FAA to consider in its cost analysis, it is not necessary to reopen the comment period or provide additional information in the AD docket. The FAA did not change this AD as a result of this comment. 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 Transport Canada AD CF-2024-37 specifies procedures for replacing the existing fuel transfer float valves and O-rings on the left and right wing with new fuel transfer float valves and O-rings and performing operational tests of the center-to-wing fuel transfer. Transport Canada AD CF-2024-37 also specifies that inserting a copy of Transport Canada AD CF-2024-37 into the ETOPS Configuration, Maintenance, and Procedures (CMP) or using ETOPS CMP issue 009.00 or later is an acceptable method of compliance. 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. Costs of Compliance The FAA estimates that this AD affects 35 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: Estimated Costs for Required Actions Labor cost Parts cost Cost per product Cost on U.S. operators Up to 16 work-hours × $85 per hour = $1,360 Unknown * Up to $1,360 Up to $47,600. * The FAA has received no definitive data on which to base the cost estimate for the parts specified in this AD. The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some or all of the costs of this 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 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: (1) Is not a "significant regulatory action" under Executive Order 12866, (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. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. The Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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 [Amended] 2. The FAA amends § 39.13 by adding the following new airworthiness directive: 2026-04-04 Airbus Canada Limited Partnership (Type Certificate Previously Held by C Series Aircraft Limited Partnership (CSALP); Bombardier, Inc.): Amendment 39-23264; Docket No. FAA-2025-2545; Project Identifier MCAI-2024-00657-T. (a) Effective Date This airworthiness directive (AD) is effective April 8, 2026. (b) Affected ADs None. (c) Applicability This AD applies to Airbus Canada Limited Partnership (type certificate previously held by C Series Aircraft Limited Partnership (CSALP); Bombardier, Inc.) Model BD-500-1A10 and BD-500-1A11 airplanes, certificated in any category, as identified in Transport Canada AD CF-2024-37, dated November 4, 2024 (Transport Canada AD CF-2024-37). (d) Subject Air Transport Association (ATA) of America Code 28, Fuel. (e) Unsafe Condition This AD was prompted by reports of certain fuel transfer float valves failing in the closed position, preventing normal fuel transfer between the center and wing fuel tanks. The FAA is issuing this AD to address the simultaneous failure of both fuel transfer float valves in the closed position during an extended-range twin-engine operation performance standards (ETOPS) flight. The unsafe condition, if not addressed, during an ETOPS flight, could lead to a forced diversion or fuel starvation and engine shutdown before reaching a diversion airport. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Requirements Except as specified in paragraph (h) of this AD: Comply with all required actions and compliance times specified in, and in accordance with, Transport Canada AD CF-2024-37. (h) Exceptions to Transport Canada AD CF-2024-37 (1) Where Transport Canada AD CF-2024-37 refers to its effective date, this AD requires using the effective date of this AD. (2) Where Transport Canada AD CF-2024-37 refers to hours air time, this AD requires using flight hours. (3) Where paragraph B. of Transport Canada AD CF-2024-37 specifies "thereafter, operating that aeroplane accordingly," this AD does not require that action as that action is already required by existing FAA operating regulations (see 14 CFR 121.374(n)). (4) Where the material referenced in Transport Canada AD CF-2024-37 specifies discarding parts, this AD requires removing those parts from service. (i) Additional AD Provisions The following provisions also apply to this AD: (1) Alternative Methods of Compliance (AMOCs): The Manager, AIR-520, Continued Operational Safety 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 responsible Flight Standards Office, as appropriate. If sending information directly to the manager of the Continued Operational Safety Branch, send it to the attention of the person identified in paragraph (j) of this AD and email to: AMOC@faa.gov . Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office. (2) Contacting the Manufacturer: For any requirement in this AD to obtain instructions from a manufacturer, the instructions must be accomplished using a method approved by Manager, AIR-520, Continued Operational Safety Branch, FAA; or Transport Canada; or Airbus Canada Limited Partnership's Transport Canada Design Approval Organization (DAO). If approved by the DAO, the approval must include the Designee's authorized signature. (j) Additional Information For more information about this AD, contact Joseph Catanzaro, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 516-228-7366; email: joseph.catanzaro@faa.gov. (k) 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) Transport Canada AD CF-2024-37, dated November 4, 2024. (ii) [Reserved] (3) For Transport Canada material identified in this AD, contact Transport Canada, Transport Canada National Aircraft Certification, 159 Cleopatra Drive, Nepean, Ontario K1A 0N5, Canada; telephone 888-663-3639; email TC.AirworthinessDirectives-Consignesdenavigabilite.TC@tc.gc.ca. You may find this material on the Transport Canada website at tc.canada.ca/en/aviation. (4) You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195. (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 fr.inspection@nara.gov. Issued on February 17, 2026. Peter A. White, Deputy Director, Integrated Certificate Management Division, Aircraft Certification Service.