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-2026-4634; Project Identifier MCAI-2024-00508-T” 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 John Massey, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 516-228-7320; email: John.A.Massey@faa.gov. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

Background

The FAA issued AD 2022-25-05, Amendment 39-22261 (87 FR 77487, December 19, 2022) (AD 2022-25-05), ( printed page 25810) for certain Airbus Canada Limited Partnership Model BD-500-1A10 and BD-500-1A11 airplanes. AD 2022-25-05 was prompted by an MCAI originated by Transport Canada, which is the aviation authority for Canada. Transport Canada issued AD CF-2021-43, dated November 29, 2021 (Transport Canada AD CF-2021-43), to correct an unsafe condition.

AD 2022-25-05 requires repetitive cleaning and greasing of all slat tracks to prevent damage or corrosion; doing repetitive inspections of the slat tracks for any damage or corrosion, and the correct application of grease; and applicable corrective actions. The FAA issued AD 2022-25-05 to address corrosion and wear on the slat tracks, which could lead to loss of one or more slat panels or loss of slat track guidance and, consequently, cause catastrophic structural damage to the wings or other parts of the airplane due to slat panels departing from the airplane.

Actions Since AD 2022-25-05 Was Issued

Since the FAA issued AD 2022-25-05, Transport Canada superseded Transport Canada AD CF-2021-43 and issued Transport Canada AD CF-2024-26, dated July 17, 2024 (Transport Canada AD CF-2024-26), and then superseded Transport Canada AD CF-2024-26 and issued Transport Canada AD CF-2025-61, dated November 24, 2025 (Transport Canada AD CF-2025-61) (also referred to as the MCAI), to correct an unsafe condition for certain Airbus Canada Limited Partnership Model BD-500-1A10 and BD-500-1A11 airplanes. The MCAI states that since Transport Canada AD CF-2021-43 was issued, it has been discovered that previous slat track repairs required the use of inappropriate NDT methods and, therefore, may have allowed cracks to remain undetected on slat tracks that were previously repaired. The MCAI states that reports have been received that the accomplishment instructions in the referenced service bulletin are ambiguous and that access constraints prevent the accomplishment of the service bulletin without the removal of all slat tracks from the airplane. The MCAI also states that since AD CF-2021-43 was issued, the manufacturer has revised the service information to specify procedures for a rework NDT inspection on all slat tracks that were previously repaired using an inappropriate NDT method, clarify the accomplishment instructions, and limit the repeat inspection and greasing of all slat tracks to visible portions of the slat tracks only.

Since Transport Canada AD CF-2024-26 was issued, Transport Canada has determined that the compliance times in Transport Canada AD CF-2024-26 need to be updated. The MCAI maintains the requirements of Transport Canada AD CF-2024-26 and updates the compliance times to consider airplanes in storage or airplanes operated under the low utilization maintenance program.

The FAA is proposing 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-2026-4634.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Transport Canada AD CF-2025-61, which specifies procedures for repetitive cleaning and greasing of all slat tracks, including the slat track rollers, the slat pinion gear bearings, and the slat pinion gears to prevent damage ( e.g., Reametal wear) and corrosion; repetitive general visual inspections (GVIs) of the slat tracks for any damage or corrosion, and correct application of grease; and applicable on-condition actions. On-condition actions include reworking and treating the area with either phosphate pre-treatment or silane pre-treatment if damage consists of abrasion, scratches, corrosion, or nicks, and performing a magnetic particle inspection (MPI) or high-frequency eddy current (HFEC) on the repair area of the slat track. Transport Canada AD CF-2025-61 also specifies procedures for an alternative method of compliance for the inspections.

The FAA also reviewed Spirit AeroSystems Service Bulletin 500SHW-57-4201, Issue No. 003, dated June 17, 2025, which specifies procedures for cleaning, inspecting, and greasing of slat tracks and applicable on-condition repairs.

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 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 in other products of the same type design.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified in Transport Canada AD CF-2025-61 described previously, except for any differences identified as exceptions in the regulatory text of this proposed 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 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 Transport Canada AD CF-2025-61 by reference in the FAA final rule. This proposed AD would, therefore, require compliance with Transport Canada AD CF-2025-61 in its entirety through that incorporation, except for any differences identified as exceptions in the regulatory text of this proposed AD. Material required by Transport Canada AD CF-2025-61 for compliance will be available at regulations.gov under Docket No. FAA-2026-4634 after the FAA final rule is published.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 161 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed 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 these on-condition actions:

The FAA has received no definitive data on which to base the cost estimates for the on-condition repairs specified in this proposed AD.

According to the manufacturer, some or all of the costs of this proposed AD may be covered under warranty, thereby reducing the cost impact on affected operators. The FAA does not control warranty coverage for affected operators. As a result, the FAA has included all known costs in the cost estimate.

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.

The Proposed Amendment

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

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

2. The FAA amends § 39.13 by:

a. Removing Airworthiness Directive (AD) 2022-25-05, Amendment 39-22261 ( 87 FR 77487, December 19, 2022); and

b. Adding the following new AD:

Airbus Canada Limited Partnership (Type Certificate Previously Held by C Series Aircraft Limited Partnership (CSALP); Bombardier, Inc.): Docket No. FAA-2026-4634; Project Identifier MCAI-2024-00508-T.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by June 26, 2026.

(b) Affected ADs

This AD replaces AD 2022-25-05, Amendment 39-22261 (87 FR 77487, December 19, 2022) (AD 2022-25-05).

(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-2025-61, dated November 24, 2025 (Transport Canada AD CF-2025-61).

(d) Subject

Air Transport Association (ATA) of America Code 57, Wings.

(e) Unsafe Condition

This AD was prompted by a report that corrosion and wear were discovered on the slat tracks due to insufficient grease applied to the slat tracks during production, and the discovery that previous slat track repairs required the use of inappropriate non-destructive test (NDT) methods and, therefore, may have allowed cracks to remain undetected on slat tracks that were previously repaired. The FAA is issuing this AD to address corrosion and wear on the slat tracks, which could lead to loss of one or more slat panels or loss of slat track guidance. The unsafe condition, if not addressed, could result in catastrophic structural damage to the wings or other parts of the airplane due to slat panels departing from the airplane.

(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, Transport Canada AD CF-2025-61. ( printed page 25812)

(h) Exception to Transport Canada AD CF-2025-61

(1) Where Transport Canada AD CF-2025-61 refers to its effective date, this AD requires using the effective date of this AD.

(2) Where Transport Canada CF-2025-61 specifies accomplishing actions in accordance with “the VSB,” this AD requires using Spirit AeroSystems Service Bulletin 500SHW-57-4201, Issue No. 003, dated June 17, 2025.

(3) Where Transport Canada CF-2025-61 refers to hours air time, this AD requires using flight hours.

(4) Where Transport Canada AD CF-2025-61 defines Group B as airplanes with “more than 2550 total hour air time”, this AD requires replacing that text with “equal to or more than 2,550 total flight hours”.

(5) Where Transport Canada AD CF-2025-61 specifies to accomplish certain actions using both the “applicable SB” and “the VSB” as defined in Transport Canada AD CF-2025-61, this AD requires using only “the VSB”.

(6) Where Transport Canada AD CF-2025-61 specifies accomplishing certain actions using “the VSB”, for this AD replace the text “Part A of the VSB” with “section 2., Procedure, of Part A of the VSB” and replace the text “Part B of the VSB” with “section 2., Procedure, of Part B of the VSB”.

(i) No Reporting Requirement

Although the material referenced in Transport Canada AD CF-2025-61 specifies to submit certain information to the manufacturer, this AD does not include that requirement.

(j) 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 International Validation Branch, send it to the attention of the person identified in paragraph (k) of this AD and email to: AMOC@faa.gov.

(i) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office.

(ii) AMOCs approved previously for AD 2022-25-05 are not approved as AMOCs for the corresponding provisions of Transport Canada AD CF-2025-61 that are required by paragraph (g) of this AD.

(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 the 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 DAO-authorized signature.

(k) Additional Information

For more information about this AD, contact John Massey, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 516-228-7320; email: John.A.Massey@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 this AD specifies otherwise.

(i) Transport Canada AD CF-2025-61, dated November 24, 2025.

(ii) Spirit AeroSystems Service Bulletin 500SHW-57-4201, Issue No. 003, dated June 17, 2025.

(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) For Spirit AeroSystems material identified in this AD, contact Short Brothers plc (Spirit AeroSystems Belfast) Airport Road, Belfast Co. Down Northern Ireland, BT3 9DZ phone 44 (0)28 9045 8444; email mro@spiritaero.com. You may find this material on the Spirit AeroSystems website at www.mro.spiritaero.com.

(5) 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.

(6) 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.

91 FR 25809