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Airworthiness Directives; Diamond Aircraft Industries Inc. Airplanes

A Rule by the Federal Aviation Administration on 03/26/2026

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• Public Inspection Published Document: 2026-05883 (91 FR 14643) Document Headings ###### Department of Transportation

Federal Aviation Administration

1. 14 CFR Part 39
2. [Docket No. FAA-2025-5397; Project Identifier MCAI-2025-00972-A; Amendment 39-23291; AD 2026-06-03]
3. RIN 2120-AA64

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule.

SUMMARY:

The FAA is superseding Airworthiness Directive (AD) 2020-14-06, which applied to all Diamond Aircraft Industries Inc. (DAI) Model DA 40, DA 40 F, and DA 40 NG airplanes. AD 2020-14-06 required replacing affected parts, inspecting the fuel tank chambers, and removing rubber material that has detached from the fuel tank connection hoses. AD 2020-14-06 also prohibited installing an affected part on any airplane. Since the FAA issued AD 2020-14-06, additional affected parts installed during production on Model DA 40 NG airplanes have been reported. As a result, the manufacturer has published updated service material for the Model DA 40 NG. This AD requires the same actions as AD 2020-14-06 and requires updated service material to be used for the Model DA 40 NG airplanes. The FAA is issuing this AD to address the unsafe condition on these products.

DATES:

This AD is effective April 30, 2026.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of April 30, 2026.

The Director of the Federal Register approved the incorporation by reference of certain other publications listed in this AD as of August 4, 2020 (85 FR 42687, July 15, 2020).

ADDRESSES:

AD Docket: You may examine the AD docket at regulations.gov under Docket No. FAA-2025-5397; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, the mandatory continuing airworthiness information (MCAI), any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

Material Incorporated by Reference:

• For Diamond Aircraft Industries material identified in this AD, contact DAI, 1560 Crumlin Sideroad, London, Ontario, Canada, N5V 1S2; phone: (519) 457-4041, fax: (519) 457-4045; email: support-canada@diamondaircraft.com.
• 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. It is also available at regulations.gov under Docket No. FAA-2025-5397.

FOR FURTHER INFORMATION CONTACT:

Joseph Catanzaro, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7366; email: joseph.catanzaro@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2020-14-06, Amendment 39-21160 (85 FR 42687, July 15, 2020), (AD 2020-14-06). AD 2020-14-06 applied to DAI Model DA 40, DA 40 F, and DA 40 NG airplanes (including Model DA 40 NG airplanes that have been converted from the Model DA 40 D). AD 2020-14-06 required replacing affected parts, inspecting the fuel tank chambers, and removing rubber material that has detached from the fuel tank connection hoses. AD 2020-14-06 also prohibited installing an affected part on any airplane. The FAA issued AD 2020-14-06 to detect and prevent fuel starvation and reduced control of the airplane. AD 2020-14-16 was prompted by Transport Canada CF-2019-39, dated October 31, 2019 (Transport Canada AD CF-2019-39) issued by Transport Canada, which is the aviation authority for Canada.

The NPRM was published in the Federal Register on December 23, 2025 (90 FR 60031). The NPRM was prompted by Transport Canada AD CF-2019-39R1, dated May 21, 2025 (also referred to as the MCAI), which superseded Transport Canada AD CF-2019-39 based on reports of additional affected parts installed during production on DAI Model DA 40 NG airplanes. As a result, the manufacturer published updated service material for the Model DA 40 NG. The MCAI also continues to require replacing affected fuel tank connection hoses, inspecting the fuel tank chambers, and removing rubber material that has detached from the fuel tank connection hoses.

In the NPRM, the FAA proposed to require the same actions as AD 2020-14-06 and to require updated service material to be used for the Model DA 40 NG airplanes.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2025-5397.

Discussion of Final Airworthiness Directive

Comments

The FAA received no comments on the NPRM or on the determination of the costs.

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, and any other changes described previously, 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 Diamond Aircraft Industries Mandatory Service Bulletin ( printed page 14644) No. MSB 40NG-064 Rev. 3, dated January 23, 2025, which specifies procedures for replacing affected parts, inspecting the fuel tank chambers, and removing rubber material that has detached from the hoses. This material also specifies the service centers from which the affected parts could have been obtained and the serial numbers for additional DAI Model DA 40 NG airplanes that are affected by the unsafe condition and were not in the previous version of the material.

This AD also requires the following Diamond Aircraft Industries Mandatory Service Bulletins, which the Director of the Federal Register approved for incorporation by reference as of August 4, 2020 (85 FR 42687, July 15, 2020):

• Diamond Aircraft Industries Mandatory Service Bulletin No. MSB 40-087, Revision 3, dated November 5, 2019.
• Diamond Aircraft Industries Mandatory Service Bulletin No. MSB F4-037, Revision 3, dated November 5, 2019.
• Diamond Aircraft Industries Work Instruction WI-MSB 40-087, Revision 0, dated July 1, 2019.
• Diamond Aircraft Industries Work Instruction WI-MSB F4-037, Revision 0, dated July 1, 2019.
• Diamond Aircraft Industries Work Instruction WI-MSB 40 NG-064, Revision 0, dated July 1, 2019. 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 987 airplanes of U.S. registry.

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

| Action | Labor cost | Parts cost | Cost per
product | Cost on U.S.
operators |
| --- | --- | --- | --- | --- |
| Inspect the fuel tank chambers | 1 work-hour × $85 per hour = $85 | $0 | $85 | $83,895 |
| Remove detached rubber material | 5 work hours × $85 per hour = $425 | 0 | 425 | 419,475 |
| Replace fuel tank connection hose | 10 work hours × $85 per hour = $850 | 383 | 1,233 | 1,216,971 |
The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some 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

The FAA has determined that 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:

a. Removing Airworthiness Directive 2020-14-06, Amendment 39-21160 (85 FR 42687, July 15, 2020); and

b. Adding the following new airworthiness directive:

2026-06-03  Diamond Aircraft Industries Inc: Amendment 39-23291; Docket No. FAA-2025-5397; Project Identifier MCAI-2025-00972-A.

(a) Effective Date

This airworthiness directive (AD) is effective April 30, 2026.

(b) Affected ADs

This AD replaces AD 2020-14-06, Amendment 39-21160 (85 FR 42687, July 15, 2020); (AD 2020-14-06).

(c) Applicability

This AD applies to all Diamond Aircraft Industries Inc. Model DA 40, DA 40 F, and DA 40 NG airplanes (including Model DA 40 NG airplanes that have been converted from the Model DA 40 D), certificated in any category.

(d) Subject

Joint Aircraft System Component (JASC) Code 1410, Hoses and tubes.

(e) Unsafe Condition

This AD was prompted by reports of fuel tank connection hose deterioration and reports of affected parts that were installed during production on Model DA 40 NG airplanes. The FAA is issuing this AD to detect and address such deterioration, which, if not corrected, could result in contamination of the fuel system and restriction of fuel flow and could lead to fuel starvation and reduced control of the airplane.

(f) Compliance

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

(g) Definitions

For the purpose of this AD, “affected part” means a fuel tank connection hose that meets the criteria in paragraph (g)(1), (2), or (3) of this AD.

(1) Part number (P/N) D4D-2817-10-70 installed during production on Model DA 40 NG airplanes with a serial number listed in ( printed page 14645) Section I.2. of Diamond Aircraft Industries Mandatory Service Bulletin MSB 40NG-064 Rev. 3, dated January 23, 2025; or

(2) P/N D4D-2817-10-70 or BENOLPRESS (no part number) purchased between July 13, 2017, and February 26, 2019, as listed in Section I.11 of Diamond Aircraft Industries Mandatory Service Bulletin No. MSB 40-087, Revision 3, dated November 5, 2019; Diamond Aircraft Industries Mandatory Service Bulletin No. MSB 40NG-064 Rev. 3, dated January 23, 2025; or Diamond Aircraft Industries Mandatory Service Bulletin No. MSB F4-037, Revision 3, dated November 5, 2019; or

(3) P/N D4D-2817-10-70 installed as a replacement part on or after July 13, 2017, if it is unknown whether the part meets the criteria in paragraph (g)(1) or (2) of this AD.

(h) Required Actions

Within 100 hours time-in-service or within 2 months, whichever occurs first after the effective date of this AD, replace each affected part as defined in paragraph (g) of this AD, inspect the main fuel tank chambers, and remove any detached rubber material in accordance with Sections III.1 and III.2 of the Instructions in Diamond Aircraft Industries Work Instruction WI-MSB 40-087, Revision 0, dated July 1, 2019; Diamond Aircraft Industries Work Instruction WI-MSB F4-037, Revision 0, dated July 1, 2019; or Diamond Aircraft Industries Work Instruction WI-MSB 40NG-064, Revision 0, dated July 1, 2019; as applicable to your model airplane.

(i) No Reporting Requirement

Although the service material specifies to submit information to the manufacturer, this AD does not require that action.

(j) Installation Prohibition

As of the effective date of this AD, do not install an affected part, as defined in paragraph (g) of this AD, on any airplane.

(k) Credit for Previous Actions

This paragraph provides credit for the actions required by paragraph (h) of this AD if those actions were performed before the effective date of this AD, and the affected part for the Model DA 40 NG airplane was identified using Diamond Aircraft Industries Mandatory Service Bulletin No. MSB 40NG-064, Revision 2, dated August 29, 2019.

(l) Alternative Methods of Compliance (AMOCs)

(1) 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)(1) of this AD and email it to: AMOC@faa.gov.

(2) 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

(1) For more information about this AD, contact Joseph Catanzaro, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7366; email: joseph.catanzaro@faa.gov.

(2) Material identified in this AD that is not incorporated by reference is available at the address specified in paragraph (n)(5) of this AD.

(n) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) 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.

(3) The following material was approved for IBR on April 30, 2026.

(i) Diamond Aircraft Industries Mandatory Service Bulletin MSB 40NG-064 Rev. 3, dated January 23, 2025.

(ii) [Reserved]

(4) The following material was approved for IBR on August 4, 2020 (85 FR 42687, July 15, 2020).

(i) Diamond Aircraft Industries Mandatory Service Bulletin No. MSB 40-087, Revision 3, dated November 5, 2019.

(ii) Diamond Aircraft Industries Mandatory Service Bulletin No. MSB F4-037, Revision 3, dated November 5, 2019.

(iii) Diamond Aircraft Industries Work Instruction WI-MSB 40-087, Revision 0, dated July 1, 2019.

(iv) Diamond Aircraft Industries Work Instruction WI-MSB 40NG-064, Revision 0, dated July 1, 2019.

(v) Diamond Aircraft Industries Work Instruction WI-MSB F4-037, Revision 0, dated July 1, 2019.

(5) 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, fax: (519) 457-4045; email: support-canada@diamondaircraft.com.

(6) 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.

(7) 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 March 18, 2026.

Steven W. Thompson,

Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.

[FR Doc. 2026-05883 Filed 3-25-26; 8:45 am]

BILLING CODE 4910-13-P

Published Document: 2026-05883 (91 FR 14643)