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-2026-13807; Project Identifier MCAI-2026-00620-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 Camille Seay, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 817-222-5149; email: Camille.L.Seay@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 2021-13-20, Amendment 39-21625 (86 FR 38223, July 20, 2021) (AD 2021-13-20), for certain Airbus Canada Limited Partnership Model BD-500-1A10 and BD-500-1A11 airplanes. AD 2021-13-20 was prompted by an MCAI originated by Transport Canada, which is the aviation authority for Canada. Transport Canada issued AD CF-2020-42, dated October 16, 2020 (Transport Canada AD CF-2020-42), to correct an unsafe condition.

AD 2021-13-20 requires inspecting the waste box, waste access doubler, and waste service door for corrosion, and doing applicable on-condition actions. The FAA issued AD 2021-13-20 to address this corrosion, which could lead to cracking or holes in the waste box or airplane skin, and consequent cabin pressure leakage and catastrophic structural damage of the airplane. ( printed page 72466)

Actions Since AD 2021-13-20 Was Issued

Since the FAA issued AD 2021-13-20, Transport Canada superseded Transport Canada AD CF-2020-42 and issued Transport Canada AD CF-2026-26, dated June 19, 2026 (Transport Canada AD CF-2026-26) (also referred to as the MCAI), to correct an unsafe condition for certain Model BD-500-1A10 and BD-500-1A11 airplanes.

The MCAI states that corrosion, caused by leakage of wastewater from the waste service panel ball valve, has been reported on the waste box, waste access doubler, and waste service door at the rear fuselage, and that some corrosion findings have been severe enough to require structural repairs or replacement of the affected parts. Since Transport Canada AD CF-2020-42 was issued, the manufacturer revised the service information, designating the existing instructions as Part A and introducing a new Part B applicable to certain airplanes; Part A improves the prior instructions ( i.e., Part A ensures a full application of secondary fuel vapor barrier to the entire waste box), and Part B adds repairs to the waste access doubler, replacement of fillet sealant, removal of corrosion-inhibiting compound, and application of secondary fuel vapor barrier (to the Part B inspection of the waste box, waste access doubler, and waste service door for corrosion, and applicable on-condition actions).

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-2026-13807.

Explanation of Retained Requirements

Although this proposed AD does not explicitly restate the requirements of AD 2021-13-20, this proposed AD would retain all of the requirements of AD 2021-13-20. Those requirements are referenced in Transport Canada AD CF-2026-26, which, in turn, is referenced in paragraph (g) of this proposed AD.

Material Incorporated by Reference Under 1 CFR Part 51

Transport Canada AD CF-2026-26 specifies procedures for a general visual inspection of the waste box, waste access doubler, and waste service door for corrosion, applying secondary fuel barrier sealant (for certain airplanes), and applicable on-condition actions. On-condition actions include repairing any corrosion found, applying secondary fuel barrier to the entire waste box, and applying corrosion protection.

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 retain all of the requirements of AD 2021-13-20. This proposed AD would require accomplishing the actions specified in Transport Canada AD CF-2026-26 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-2026-26 by reference in the FAA final rule. This proposed AD would, therefore, require compliance with Transport Canada AD CF-2026-26 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-2026-26 for compliance will be available at regulations.gov by searching for and locating Docket No. FAA-2026-13807 after the FAA final rule is published.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 32 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD:

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

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 ( printed page 72467) 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) 2021-13-20, Amendment 39-21625 ( 86 FR 38223, July 20, 2021); 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-2026-13807; Project Identifier MCAI-2026-00620-T.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by December 28, 2026.

(b) Affected ADs

This AD replaces AD 2021-13-20, Amendment 39-21625 (86 FR 38223, July 20, 2021) (AD 2021-13-20).

(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-2026-26, dated June 19, 2026 (Transport Canada AD CF-2026-26).

(d) Subject

Air Transport Association (ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

This AD was prompted by reports of corrosion on the waste box, waste access doubler, and waste service door at the aft waste service port, caused by leakage of wastewater from the waste service panel ball valve. The FAA is issuing this AD to address this corrosion, which could lead to cracking or holes in the waste box or airplane skin, and consequent cabin pressure leakage and catastrophic structural damage of the airplane.

(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-2026-26.

(h) Exception to Transport Canada AD CF-2026-26

(1) Where Transport Canada AD CF-2026-26 refers to its effective date, this AD requires using the effective date of this AD.

(2) Where Transport Canada AD CF-2026-26 refers to hours air time, this AD requires using flight hours.

(3) Where Part I of Transport Canada AD CF-2026-26 specifies a compliance time of “Within 14,200 flight cycles or 56 months from the aeroplane date of manufacture, as identified on the identification plate of the aeroplane, whichever occurs first” or “Within 9,900 flight cycles or 56 months from the aeroplane date of manufacture, as identified on the identification plate of the aeroplane, whichever occurs first”, depending on airplane configuration, to accomplish all applicable actions, this AD requires that corrosion repair be done before further flight after detection of corrosion, as identified in the applicable service information specified in Transport Canada AD CF-2026-26.

(4) Where Part II of Transport Canada AD CF-2026-26 specifies “repair any corrosion found”, for this AD, replace that text with “repair any corrosion found before further flight”.

(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 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.

(j) Additional Information

For more information about this AD, contact Camille Seay, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 817-222-5149; email: Camille.L.Seay@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-2026-26, dated June 19, 2026.

(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 98198. 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.

91 FR 72465