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 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 44337). The NPRM was prompted by AD CF-2025-09, dated February 24, 2025 (Transport Canada AD CF-2025-09) (also referred to as the MCAI), issued by Transport Canada, which is the aviation authority for Canada. The MCAI states that titanium fasteners (part number (P/N) B0206003GD) had been incorrectly installed in the butt strap at the outer wing box lower skin to center wing box interface in lieu of the correct nickel alloy fasteners (P/N B0206033GD). The use of titanium fasteners could result in a reduction in joint strength, and the risk of a fuel leak if the fastener fails and falls free from the joint. This condition, if not corrected, could cause damage to and loss of principal structure and fatigue critical structure.

In the NPRM, the FAA proposed to require the identification of fasteners installed in the butt strap at the outer wing box lower skin to center wing box interface, and applicable on-condition actions, as specified in Transport Canada AD CF-2025-09. 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-2025-2543.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from an anonymous commenter who supported the NPRM without change.

The FAA received additional comments from Delta Air Lines (Delta) and the Citizens Rulemaking Alliance. The following presents the comments ( printed page 31342) received on the NPRM and the FAA's response to each comment.

Request To Remove the Requirement To Contact the Manufacturer for Disposition

Delta requested that the FAA add an exception to paragraph (h) of the proposed AD to allow use of an existing, approved Airbus Canada Limited Partnership (ACLP) disposition instead of contacting ACLP for an approved disposition via the instructions in the service information referenced in Transport Canada AD CF-2025-09. Delta noted that ACLP is changing the contact method specified in the service information, so operators may need to request an alternative method of compliance (AMOC) to use an alternative contact method. Delta also noted that ACLP has already issued two Generic Repair Engineering Orders (GREOs) to address discrepant fasteners found during the inspection, and that the GREOs meet the provisions of paragraph (j)(2) of the proposed AD for obtaining an approved disposition.

The FAA agrees that operators may use existing repair instructions, including GREOs, for compliance with this AD provided the repair instructions were approved under the provisions of paragraph (j)(2) of this AD. No change to this AD is necessary in regard to that part of Delta's comment.

The FAA also agrees with removing the requirement to obtain an approved disposition in accordance with the contact method specified in the service information referenced in Transport Canada AD CF-2025-09 and has added a new exception in paragraph (h)(3) of this AD accordingly. The FAA notes that under paragraph (j)(2) of this AD operators must contact the Manager, AIR-520, Continued Operational Safety Branch, FAA; or Transport Canada; or ACLP's Transport Canada Design Approval Organization (DAO) to obtain an approved disposition for any requirement in this AD to obtain instructions from a manufacturer.

Request To Extend the Compliance Times

Delta requested that the FAA revise paragraph (h)(2) of the proposed AD to allow the required inspection to be accomplished within 11,400 total flight cycles, 22,800 total flight hours, or 500 flight cycles from the effective date of this AD, whichever occurs later, instead of performing the inspections within 500 flight cycles from the effective date of the AD or before accumulating 10,000 total flight cycles, whichever occurs later. Delta stated that ACLP has already issued two approved GREOs to address discrepant fasteners found during the inspection, and that one of the GREOs authorizes continued flight with the discrepant fasteners up to 11,400 total flight cycles or 22,800 total flight hours, whichever occurs first. Delta asserted that if replacement of the discrepant fasteners can be deferred to those later thresholds, then deferring the inspection to the same thresholds provides an acceptable level of safety.

The FAA disagrees with extending the compliance time for performing the inspection to determine if serviceable fasteners are installed. Transport Canada, as the state of design authority for these airplanes, analyzed the data, considered the recommendations of the manufacturers, and determined that the inspection must be accomplished before accumulating 10,000 total flight cycles or within 500 flight cycles from the effective date of the AD, whichever occurs later; and the FAA concurs with Transport Canada's determination. However, under the provisions of paragraph (j)(1) of this AD, the FAA will consider requests for approval of an extension of the compliance time if sufficient data are submitted to substantiate that the new compliance time would provide an acceptable level of safety. The FAA has not changed this AD as a result of this comment.

Request To Justify Forgoing Notice and Comment or Issue an NPRM

The Citizens Rulemaking Alliance requested that the FAA either provide its justification for finding good cause to bypass notice and comment procedures and the 30-day delayed effective date, or convert this action to an NPRM with a 30-day comment period. 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 Comply With the Paperwork Reduction Act (PRA)

The Citizens Rulemaking Alliance 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 paragraph (i) of this AD specifies that 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 Consider Impact on Small Entities

The Citizens Rulemaking Alliance requested that the FAA either provide the factual basis for its certification under the Regulatory Flexibility Act (RFA) that the AD will not have a significant economic impact on a substantial number of small entities, or prepare an initial regulatory flexibility analysis that identifies potentially affected small entities and considers alternatives that minimize impact.

The FAA provides the following clarification. The RFA of 1980 (5 U.S.C. 601-612), as amended by the Small Business Regulatory Enforcement Fairness Act of 1996 (Pub. L. 104-121) and the Small Business Jobs Act of 2010 (Pub. L. 111-240), requires Federal agencies to consider the effects of the regulatory action on small business and other small entities and to minimize any significant economic impact. The term “small entities” comprises small businesses and not-for-profit organizations that are independently owned and operated and are not dominant in their fields, and governmental jurisdictions with populations of less than 50,000.

The FAA identified three air carriers that will be affected by this AD. Based on the Small Business Administration size standard, all three entities are large businesses: ( printed page 31343)

If an agency determines that a rulemaking will not result in a significant economic impact on a substantial number of small entities, the head of the agency may so certify under section 605(b) of the RFA. Therefore, as provided in section 605(b) and based on the foregoing, the head of the FAA certifies that this AD will not result in a significant economic impact on a substantial number of small entities. The FAA did not change this AD as a result of this comment.

Request To Provide Additional Cost Information

The Citizens Rulemaking Alliance requested that the FAA augment the economic analysis to include downtime and scheduled disruption costs, parts availability constraints, and cumulative fleet impacts, and adjust the compliance times to align with scheduled maintenance intervals and broaden AMOC pathways accordingly. The commenter stated that the FAA should also provide the per airplane and fleet costs, including labor hours, parts, engineering, software loads, and special tools.

The FAA recognizes that, in doing the actions required by an AD, operators might incur indirect costs (such as engineering work or loss of revenue due to airplane downtime, scheduled disruptions, parts availability constraints, etc.) 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 costs since the FAA lacks data on those costs and they vary significantly among operators. Additionally, the FAA determined that there may be no downtime costs for some of the affected operators because the compliance times required by this AD would allow the required inspection to be performed during regularly scheduled maintenance. Further, special tools and software are not necessary to complete the actions required by this AD.

In the Costs of Compliance section of the proposed AD, the FAA disclosed the number of affected airplanes on the U.S. registry, estimated number of work hours and parts costs provided by the manufacturer, and the fleet cost. 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 provide additional information in the AD docket.

Further, in developing an appropriate compliance time for this AD, the FAA considered the compliance time in Transport Canada AD CF-2025-09, the urgency associated with the subject unsafe condition, the availability of required parts, and the practical aspect of accomplishing the required actions within a period of time that corresponds to the normal scheduled maintenance for most affected operators. However, under the provisions of paragraph (j)(1) of this AD, the FAA will consider requests for approval of an extension of the compliance time if sufficient data are submitted to substantiate that the new compliance time would provide an acceptable level of safety. 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

The FAA reviewed Transport Canada AD CF-2025-09, which specifies procedures for a detailed inspection to identify the part markings on the head of the fasteners, and applicable on-condition actions. On-condition actions include replacing non-serviceable fasteners (those not identified as HST54, HST154, HST254, B0201074, B0201074 with oversize code X, or B0201074 with oversize code Y). For non-serviceable fasteners, the replacement includes a detailed inspection to make sure that the fastener heads are not damaged; the fastener heads are installed within requirements; and there are no signs of loose fasteners, fasteners that rotated, or fasteners that moved.

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 71 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD:

The FAA estimates the following costs to do any necessary on-condition actions that would be required based on the results of any required actions. The FAA has no way of determining the number of aircraft that might need this on-condition action: ( printed page 31344)

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.

The Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

91 FR 31341