# [Amended]
**AGENCY:**
Federal Aviation Administration (FAA), DOT.
**ACTION:**
Notice of proposed rulemaking (NPRM).
**SUMMARY:**
The FAA proposes to supersede Airworthiness Directive (AD) 2020-14-06, which applies to all Diamond Aircraft Industries Inc. (DAI) Model DA 40, DA 40 F, and DA 40 NG airplanes. AD 2020-14-06 requires 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 prohibits 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 proposed AD would require the same actions as AD 2020-14-06 and would require updated service material to be used for the Model DA 40 NG airplanes. The FAA is proposing this AD to address the unsafe condition on these products.
**DATES:**
The FAA must receive comments on this NPRM by February 6, 2026.
**ADDRESSES:**
You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:
• *Federal eRulemaking Portal:* Go to *regulations.gov* . Follow the instructions for submitting comments.
• *Fax:* (202) 493-2251.
• *Mail:* U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
• *Hand Delivery:* Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
*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 NPRM, the mandatory continuing airworthiness information (MCAI), any comments received, and other information. The street address for Docket Operations is listed above.
*Material Incorporated by Reference:*
• For Diamond Aircraft Industries material identified in this proposed AD, contact DAI, 1560 Crumlin Sideroad, London, Ontario, Canada, N5V 1S2; phone: (519) 457-4041, fax: (519) 457-4045; email: *[email protected].*
• 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.
**FOR FURTHER INFORMATION CONTACT:**
Joseph Catanzaro, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7366; email: *[email protected]* .
**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-2025-5397; Project Identifier MCAI-2025-00972-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 the 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 Joseph Catanzaro, 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.
**Background**
The FAA issued AD 2020-14-06, Amendment 39-21160 (85 FR 42687, July 15, 2020) (AD 2020-14-06), for 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), all serial numbers, certificated in any category. AD 2020-14-06 was prompted by AD CF-2019-39, dated October 31, 2019 (Transport Canada AD CF-2019-39) issued by Transport Canada, which is the aviation authority for Canada. Transport Canada issued Transport Canada AD CF-2019-39 to correct an unsafe condition identified as fuel tank connection hose deterioration.
AD 2020-14-06 requires 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 prohibits installing an affected part on any airplane. The FAA issued AD 2020-14-06 to detect deterioration of fuel tank connection hoses, 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.
**Actions Since AD 2020-14-06 Was Issued**
Since the FAA issued AD 2020-14-06, Transport Canada superseded Transport Canada AD CF-2019-39 and issued Transport Canada AD CF-2019-39R1, dated May 21, 2025 (also referred to as the MCAI). The MCAI states that since the issuance of Transport Canada AD CF-2019-39, Transport Canada has received reports of 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.
You may examine the MCAI in the AD docket at *regulations.gov* under Docket No. FAA-2025-5397.
**Material Incorporated by Reference Under 1 CFR Part 51**
The FAA reviewed Diamond Aircraft Industries Mandatory Service Bulletin 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 proposed AD would also require 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.
**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 the same actions as AD 2020-14-06 and would require updated material to be used for the Model DA 40 NG airplanes.
**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:
| Action | Labor cost | Parts cost | Cost per | Cost on U.S. |
| --- | --- | --- | --- | --- |
| 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 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 that the 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.
**List of Subjects in 14 CFR Part 39**
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
**The Proposed Amendment**
Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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
2. The FAA amends § 39.13 by:
a. Removing Airworthiness Directive AD 2020-14-06, Amendment 39-21160 (85 FR 42687, July 15, 2020); and
b. Adding the following new airworthiness directive:
*Diamond Aircraft Industries Inc.:* Docket No. FAA-2025-5397; Project Identifier MCAI-2025-00972-A.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by February 6, 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**
(1) For the purpose of this AD, “affected part” means a fuel tank connection hose that meets the criteria in paragraph (g)(1)(i), (ii), or (iii) of this AD.
(i) Part number (P/N) D4D-2817-10-70 installed during production on Model DA 40 NG airplanes with a serial number listed in Section I.2. of Diamond Aircraft Industries Mandatory Service Bulletin MSB 40NG-064 Rev. 3, dated January 23, 2025; or
(ii) 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
(iii) 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)(i) or (ii) 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: *[email protected].*
(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: *[email protected].*
(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 February 6, 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: *[email protected].*
(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 *[email protected].*
Issued on December 16, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.