AD 2025-23-51

This AD is effective on December 1, 2025. Emergency AD 2025-23-51, issued on November 8, 2025, which contains the requirements of this amendment, was effective with actual notice.

The FAA must receive comments on this AD by December 29, 2025.

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 by searching for and locating Docket No. FAA-2025-4002; 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, any comments received, and other information. The street address for Docket Operations is listed above.

Brian Knaup, Manager, AIR-520, Continued Operational Safety Branch, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 817-222-5390; email: OperationalSafety@faa.gov.

The FAA invites you to send any written relevant data, views, or arguments about this AD. Send your comments using a method listed under the ADDRESSES section. Include “Docket No. FAA-2025-4002; Project Identifier AD-2025-01671-T” 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 Brian Knaup, Manager, AIR-520, Continued Operational Safety Branch, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 817-222-5390; email: OperationalSafety@faa.gov. Any commentary that the FAA receives that is not specifically designated as CBI will be placed in the public docket for this rulemaking.

The FAA issued Emergency AD 2025-23-51, dated November 8, 2025 (Emergency AD 2025-23-51), to address an unsafe condition on all The Boeing Company Model MD-11 and MD-11F airplanes. The FAA sent the emergency AD to all known U.S. owners and operators of these airplanes. Emergency AD 2025-23-51 prohibits further flight until the airplane is inspected and all applicable corrective actions are performed using a method approved by the FAA.

Emergency AD 2025-23-51 was prompted by an accident where the left-hand engine and pylon detached from the airplane during takeoff. The cause of the detachment is currently under investigation. This condition could result in loss of continued safe flight and landing.

The FAA is issuing this AD because the agency has determined the unsafe condition is likely to exist or develop in other products of the same type design.

This AD prohibits further flight until the airplane is inspected and all applicable corrective actions are performed using a method approved by the Manager, AIR-520, Continued Operational Safety Branch, FAA.

The FAA considers this AD to be an interim action. If final action is later identified, the FAA might consider further rulemaking then.

Section 553(b) of the Administrative Procedure Act (APA) (5 U.S.C. 551 et seq.) authorizes agencies to forgo 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.

An unsafe condition exists that required the immediate adoption of Emergency AD 2025-23-51 issued on November 8, 2025, to all known U.S. owners and operators of these airplanes. The FAA found that the risk to the flying public and safety in air commerce justified forgoing notice and comment prior to adoption of this rule because the severity of the unsafe condition necessitates prohibiting further flight until the airplane is inspected and the applicable corrective actions are performed. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to 14 CFR 39.13 to make it effective to all persons. Given the significance of the risk presented by this unsafe condition, it must be immediately addressed. Accordingly, notice and opportunity for prior public comment are impracticable and contrary to the public interest pursuant to 5 U.S.C. 553(b).

In addition, 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, for the same reasons the FAA found good cause to forgo notice and comment.

The requirements of the 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 notice and comment, RFA analysis is not required.

The FAA estimates that this AD affects 109 airplanes of U.S. registry. The FAA has no definitive data on which to base the cost estimates for the inspection and corrective actions specified in this AD.

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: