AD 2026-04-02

This AD is effective March 19, 2026.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of March 19, 2026.

The FAA must receive comments on this AD by April 20, 2026.

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-2026-1321; 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 street address for Docket Operations is listed above.

Material Incorporated by Reference:

• For Rotax material identified in this AD, contact Rotax, Rotaxstrasse 1, Gunskirchen, Austria; phone: +43 7246 601 0; website: www.flyrotax.com.

• You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 1200 District Avenue, Burlington, MA 01803. 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-2026-1321.

David Bergeron, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (860) 386-1805; email: david.j.bergeron@faa.gov.

The FAA invites you to send any written data, views, or arguments about this final rule. Send your comments using a method listed under the ADDRESSES section. Include “Docket No. FAA-2026-1321; Project Identifier MCAI-2025-01769-E” at the beginning of your comments. The most helpful comments reference a specific portion of the final rule, 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 final rule 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 final rule.

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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to David Bergeron, 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.

The European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA Emergency AD 2025-0267-E, dated November 28, 2025 (EASA AD 2025-0267-E) (also referred to as the MCAI), to correct an unsafe condition on Rotax Model 915 iSc2 A, 915 iSc3 A, 915 iSc2 C24, 915 iSc3 C24, 916 iSc2 A, 916 iSc3 A, 916 iSc3 B, 916 iSc2 C24, and 916 iSc3 C24 engines. The MCAI states that an occurrence was reported of the M40 x 1.5 collar nut that had not been installed on the propeller gearbox of a recently manufactured engine, which could result in the propeller shaft being pulled out of the gearbox housing during operation. To address this potential unsafe condition, Rotax published service material to provide instructions for inspection of the propeller gearbox and corrective action if the M40 x 1.5 collar nut is not installed on the propeller gearbox. This condition, if not detected and corrected, could lead to an in-flight engine failure and loss of propeller retention, possibly resulting in loss of control of the airplane.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2026-1321.

The FAA reviewed Rotax Alert Service Bulletin ASB-915 i-021R1/ASB-916 i-009R1, Revision 1, dated November 27, 2025 (published as a single document) (Rotax ASB-915 i-021R1/ASB-916 i-009R1), which specifies procedures for a visual inspection of the propeller gearbox to determine if a collar nut is installed on the propeller shaft and, if not installed, replacement of the propeller gearbox with a serviceable propeller gearbox.

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.

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 AD after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

This AD requires accomplishing the actions specified in the material already described, except as discussed under “Differences Between This AD, the MCAI, and the Referenced Material.”

Where EASA AD 2025-0267-E applies to Rotax Model 915 iSc2 A, 915 iSc3 A, 916 iSc2 A, 916 iSc3 A, 916 iSc3 B, 916 iSc2 C24, and 916 iSc3 C24 engines, all serial numbers, this AD does not, as these engine models do not have an FAA type certificate. Although none of these models are listed on the current FAA type certificate, certain Rotax Model 915i and 916i series engines are undergoing FAA validation towards FAA type certification.

Where Rotax ASB-915 i-021R1/ASB-916 i-009R1 specifies “If contamination is found, contact your local ROTAX Authorized Distributors or their independent Service Centers,” this AD requires, before further flight, accomplishing further action in accordance with a method approved by the Manager, International Validation Branch, FAA; EASA; or Rotax' EASA Design Organization Approval (DOA). If approved by the DOA, the approval must include the DOA-authorized signature.

Section 553(b) of the Administrative Procedure Act (APA) (5 U.S.C. 551 et seq.) authorizes agencies to dispense with notice and comment procedures for rules when the agency, for “good cause,” finds that those procedures are “impracticable, unnecessary, or contrary to the public interest.” Under this section, an agency, upon finding good cause, may issue a final rule without providing notice and seeking comment prior to issuance. Further, section 553(d) of the APA authorizes agencies to make rules effective in less than thirty days, upon a finding of good cause.

The FAA justifies waiving notice and comment prior to adoption of this rule because no domestic operators are affected by this AD. It is unlikely that the FAA will receive any adverse comments or useful information about this AD from any U.S. operator.

Accordingly, notice and opportunity for prior public comment are unnecessary, pursuant to 5 U.S.C. 553(b). In addition, for the foregoing reason(s), the FAA finds that good cause exists pursuant to 5 U.S.C. 553(d) for making this amendment effective in less than 30 days.

The requirements of the Regulatory Flexibility Act (RFA) do not apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt a rule without prior notice and comment. Because the FAA has determined that it has good cause to adopt this rule without prior notice and comment, RFA analysis is not required.

There are no costs of compliance with this AD because there are no engines with this type certificate on the U.S. Registry.

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.

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, and

(2) Will not affect intrastate aviation in Alaska.

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

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

2. The FAA amends § 39.13 by adding the following new airworthiness directive: