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 ADDRESSES . Include “Docket No. FAA-2026-4633; Project Identifier MCAI-2025-01173-A” 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 Fatin Saumik, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking. ( printed page 26953)

Background

Transport Canada, which is the aviation authority for Canada, has issued Transport Canada AD CF-2025-30, dated June 23, 2025 (Transport Canada AD CF-2025-30) (also referred to as the MCAI), to correct an unsafe condition on all DAI Model DA 40, DA 40 D, DA 40 F, and DA 40 NG airplanes. The MCAI states that DAI received several reports of passenger door separation. DAI attributed the root cause of certain instances to the passenger door not being properly latched and subsequent attempts to latch the passenger door in flight. DAI was unable to find a definitive root cause of the remaining occurrences. Passenger door separation, if not addressed, could result in damage to the airplane structure and lead to loss of control of the airplane and injury to persons on the ground. The MCAI requires updating the AFM, modifying the airplane in the passenger door latching mechanism and safety hook mechanism areas, repetitively inspecting the door latching and safety hook mechanisms, and reporting all findings to DAI.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2026-4633.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Diamond Aircraft Mandatory Service Bulletin MSB 40-103/MSB F4-042/MSB D4-114/MSB 40NG-084 REV. 2, dated June 5, 2025 (issued as one document), published with Diamond Aircraft Work Instruction WI-MSB 40-103/WI-MSB F4-042/WI-MSB D4-114/WI-MSB 40NG-084 REV. 2, dated June 5, 2025 (issued as one document). This material specifies procedures for inspecting the passenger door latching mechanism and safety hook mechanism areas and performing corrective action, as applicable; inspecting the safety hook, latching bolts, front and rear door guide blocks, canopy and passenger door warning light, carbon hinges, tension spring, retaining block, safety hook push button, latching mechanism spring, gas spring, and door frame; measuring the passenger door handle actuation force; modifying the airplane with placards; replacing the gas spring; and replacing the hook assembly, retaining block, door guide blocks, and door sealant if necessary for Model DA 40, DA 40 F, and DA 40 NG airplanes.

The FAA also reviewed Diamond Aircraft DA 40 AFM Doc. No. 6.01.01-E Temporary Revision TR-MAM-40-1203, Door Latching and Locking, dated December 16, 2024; Diamond Aircraft DA 40 F AFM Doc. No. 6.01.02-E Temporary Revision TR-MAM-40-1203, Door Latching and Locking, dated December 16, 2024; and Diamond Aircraft DA 40 NG AFM Doc. No. 6.01.15-E Temporary Revision TR-MAM-40-1203/a, Door Latching and Locking, dated February 18, 2025. This material specifies procedures for amending the AFM by revising the operating limitations, emergency procedures, and normal operating procedures related to door latching and locking for Model DA 40, DA 40 F, and DA 40 NG airplanes.

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 and material referenced above. The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified in the material already described, except as discussed under “Differences Between this Proposed AD and the MCAI.” The owner/operator (pilot) holding at least a private pilot certificate may revise the existing AFM for the airplane and must enter compliance with the applicable paragraph of this proposed AD into the airplane maintenance records in accordance with 14 CFR 43.9(a) and 91.417(a)(2)(v). The pilot may perform this action because it only involves revising the existing AFM. This action could be performed equally well by a pilot or mechanic. This is an exception to the FAA's standard maintenance regulations.

Differences Between This Proposed AD, the MCAI, and the Referenced Material

The MCAI applies to DAI Model DA 40 D airplanes, but this proposed AD would not include this model because it does not have an FAA type certificate.

The service bulletin referred to in the MCAI specifies to contact DAI for repair instructions, but this proposed AD would require contacting the Manager, International Validation Branch, FAA; Transport Canada; or DAI's Transport Canada Design Organization Approval (DOA) instead.

The material referenced above specifies recording any findings in the execution report and submitting the execution report to DAI, but this proposed AD does not include that requirement.

Interim Action

The FAA considers that this proposed AD would be an interim action. This unsafe condition is still under investigation by the manufacturer and, depending on the results of that investigation, the FAA may consider further rulemaking action.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 987 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this proposed AD:

( printed page 26954)

The FAA estimates the following costs to do any replacements that would be required based on the results of the proposed inspection. The agency has no way of determining the number of airplanes that might need these replacements:

The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some of the costs of this proposed 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

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 adding the following new airworthiness directive:

Diamond Aircraft Industries Inc.: Docket No. FAA-2026-4633; Project Identifier MCAI-2025-01173-A.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by June 29, 2026.

(b) Affected ADs

None.

(c) Applicability

This AD applies to all Diamond Aircraft Industries Inc. (DAI) Model DA 40, DA 40 F, and DA 40 NG airplanes, certificated in any category.

(d) Subject

Joint Aircraft System Component (JASC) Code 5210, Passenger/Crew Doors.

(e) Unsafe Condition

This AD was prompted by several reports of passenger door separation during flight. The FAA is issuing this AD to address this unsafe condition. The unsafe condition, if not addressed, could result in damage to the airplane structure and lead to loss of control of the airplane and injury to persons on the ground.

(f) Definition

For the purposes of this AD, the Diamond Aircraft work instruction is defined as Diamond Aircraft Work Instruction WI-MSB 40-103/WI-MSB F4-042/WI-MSB D4-114/WI-MSB 40NG-084 REV. 2, dated June 5, 2025 (issued as one document), published with Diamond Aircraft Mandatory Service Bulletin MSB 40-103/MSB F4-042/MSB D4-114/MSB 40NG-084 REV. 2, dated June 5, 2025 (issued as one document).

(g) Applicable Airplane Flight Manual (AFM) Temporary Revisions

The following presents the AFM and temporary revisions that apply to this AD and each individual model.

(1) For Model DA 40 airplanes: Diamond Aircraft DA 40 AFM Doc. No. 6.01.01-E Temporary Revision TR-MAM-40-1203, Door Latching and Locking, dated December 16, 2024.

(2) For Model DA 40 F airplanes: Diamond Aircraft DA 40 F AFM Doc. No. 6.01.02-E Temporary Revision TR-MAM-40-1203, Door Latching and Locking, dated December 16, 2024.

(3) For Model DA 40 NG airplanes: Diamond Aircraft DA 40 NG AFM Doc. No. 6.01.15-E Temporary Revision TR-MAM-40-1203/a, Door Latching and Locking, dated February 18, 2025.

(h) Compliance

Comply with this AD within the compliance times specified, unless already done.

(i) Required Actions

(1) Within 100 hours time-in-service (TIS) or 100 days, whichever occurs first after the effective date of this AD, revise the existing AFM for the airplane to include the information specified in the applicable AFM temporary revision specified in paragraphs (g)(1) through (3) of this AD.

(i) The owner/operator (pilot) holding at least a private pilot certificate may revise the existing AFM for the airplane and must enter compliance with the applicable paragraph of this AD into the airplane maintenance records in accordance with 14 CFR 43.9(a) and 91.417(a)(2)(v). The record must be maintained as required by 14 CFR 91.417, 121.380, or 135.439.

(ii) The AFM revision required by paragraph (i)(1) of this AD may be accomplished before the initial inspection and modification required by paragraph (i)(2) or (3) of this AD for that airplane. ( printed page 26955)

(2) For airplanes with less than 100 total hours TIS as of the effective date of this AD: Within 100 hours TIS or 100 days, whichever occurs first after the effective date of this AD, accomplish the initial inspection of the safety hook, latching bolts, front and rear door guide blocks and the modification of the airplane with placards in accordance with the instructions of Section III, steps 5, 20 through 23, 28, 30, 31, and 33 through 36 in the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD, except accomplish the actions required by step 20(f) in accordance with paragraphs (i)(4) and (5) of this AD.

(3) For airplanes that have accumulated 100 or more total hours TIS as of the effective date of this AD: Within 100 hours TIS or 100 days, whichever occurs first after the effective date of this AD, accomplish the initial inspection of the canopy and passenger door warning light, carbon hinges, safety hook, tension spring, retaining block, safety hook push button, safety hook mechanism, latching mechanism spring, gas spring, latching bolts, front and rear door guide blocks, and door frame; measure the passenger door handle actuation force; and accomplish the modification of the airplane with placards in accordance with the instructions of Section III, steps 2 through 10, 12, 13, 15, 17, 18, 20 through 24, and 28 through 36 in the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD, except accomplish the actions required by step 20(f) in accordance with paragraphs (i)(4) and (5) of this AD.

(4) If, during the inspection required by step 20(f) in the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD, the force measured is less than 1.8 kg (18 N), and if the force measured during the inspection required by step 20(c) was between 2 kg (20 N) and 6 kg (60 N), perform the following:

(i) Repeat the inspection required by step 20(c) in the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD every 100 hours TIS until the replacement of the gas spring required by paragraph (i)(4)(ii) of this AD is accomplished.

(ii) Within 12 months after the effective date of this AD, replace the gas spring in accordance with the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD.

(5) If, during the inspection specified in step 20(f) in the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD, the force measured is less than 1.8 kg (18 N), and if the force measured during the inspection required by step 20(c) was greater than 6 kg (60 N) or less than 2 kg (20 N), before further flight, replace the gas spring.

(6) If, during any inspection as required by paragraph (i)(2) or (3) of this AD, any findings, as defined in Section III, steps 5, 6, 9, 12, 20, and 23 are identified, before further flight, accomplish the applicable corrective action(s) in accordance with the instructions of Section IV, IV.1, steps 1 through 9, IV.2, steps 1 and 2, IV.3, steps 1 and 2, and IV.4, steps 1 through 5 in the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD.

(7) Where the instructions of Section III or Section IV of the Diamond Aircraft Work Instruction specified in paragraph (f) of this AD state to contact the manufacturer “in case of doubt” or for approved instructions, this AD requires before further flight, using instructions approved by the Manager, International Validation Branch, FAA; Transport Canada; or DAI's Transport Canada Design Organization Approval (DOA), and within the compliance time specified therein, accomplishing those instructions. If approved by the DOA, the approval must include the DOA-authorized signature.

(j) No Reporting Requirement

Although the material referenced in paragraph (f) of this AD specifies to submit information to the manufacturer, this AD does not require that action.

(k) Credit for Previous Actions

You may take credit for the actions required by paragraph (i) of this AD if you performed those actions before the effective date of this AD using Diamond Aircraft Mandatory Service Bulletin MSB 40-103/MSB F4-042/MSB D4-114/MSB 40NG-084 REV. 1, dated May 15, 2025 (issued as one document), published with Diamond Aircraft Work Instruction WI-MSB 40-103/WI-MSB F4-042/WI-MSB D4-114/WI-MSB 40NG-084 REV. 1, dated May 15, 2025 (issued as one document); or Diamond Aircraft Mandatory Service Bulletin MSB 40-103/MSB F4-042/MSB D4-114/MSB 40NG-084 REV. 0, dated March 20, 2025 (issued as one document), published with Diamond Aircraft Work Instruction WI-MSB 40-103/WI-MSB F4-042/WI-MSB D4-114/WI-MSB 40NG-084 REV. 0, dated March 20, 2025 (issued as one document).

(l) Alternative Methods of Compliance (AMOCs)

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 (m) 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 local flight standards district office/certificate holding district office.

(m) Additional Information

For more information about this AD, contact Fatin Saumik, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7300; email: fatin.r.saumik@faa.gov.

(n) 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) Diamond Aircraft Mandatory Service Bulletin MSB 40-103/MSB F4-042/MSB D4-114/MSB 40NG-084 REV. 2, dated June 5, 2025 (issued as one document), published with Diamond Aircraft Work Instruction WI-MSB 40-103/WI-MSB F4-042/WI-MSB D4-114/WI-MSB 40NG-084 REV. 2, dated June 5, 2025 (issued as one document).

(ii) Diamond Aircraft DA 40 Airplane Flight Manual (AFM) Doc. No. 6.01.01-E Temporary Revision TR-MAM-40-1203, Door Latching and Locking, dated December 16, 2024.

(iii) Diamond Aircraft DA 40 F AFM Doc. No. 6.01.02-E Temporary Revision TR-MAM-40-1203, Door Latching and Locking, dated December 16, 2024.

(iv) Diamond Aircraft DA 40 NG AFM Doc. No. 6.01.15-E Temporary Revision TR-MAM-40-1203/a, Door Latching and Locking, dated February 18, 2025.

(3) For Diamond Aircraft Industries material identified in this AD, contact Diamond Aircraft Industries Inc., 1560 Crumlin Sideroad, London, Ontario, Canada, N5V 1S2; phone: (519) 457-4041; email: support-canada@diamondaircraft.com; website: diamondaircraft.com.

(4) You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For information on the availability of this material at the FAA, call (817) 222-5110.

(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 26952