SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written data, views, or arguments about this final rule. Send your comments using a method listed under ADDRESSES . Include “Docket No. FAA-2026-3867; Project Identifier MCAI-2026-00403-R” 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.

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 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 Enns, 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 Emergency AD 2026-08-51, dated April 16, 2026 (Emergency AD 2026-08-51) (also referred to as the emergency AD), to address an unsafe condition on all AHD Model MBB-BK 117 D-3 helicopters. The FAA sent the emergency AD to all known U.S. owners and operators of these helicopters. The emergency AD requires inspecting the rotor hub-shaft for a crack and depending on the inspection results, replacing any rotor hub-shaft that has any cracks and reporting information after accomplishment of the replacement. The emergency AD also prohibits installing any affected rotor hub-shaft on any helicopter, unless certain requirements are met.

Emergency AD 2026-08-51 was prompted by EASA Emergency AD 2026-0078-E, dated April 13, 2026 (EASA Emergency AD 2026-0078-E) (also referred to as the MCAI), issued by EASA, which is the Technical Agent for the Member States of the European Union, to correct an unsafe condition on all AHD Model MBB-BK 117 D-3 and D-3m helicopters. The MCAI states a report of a crack on the affected part was detected after the crew reported an increased vibration of the helicopter. The MCAI defines the affected part as a rotor hub-shaft manufacturer part number D623M1501203 and D623M1501204.

The FAA is issuing this AD to address cracking of the rotor hub-shaft, which could lead to failure of the main rotor transmission and consequent loss of control of the helicopter.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2026-3867.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed EASA Emergency AD 2026-0078-E, which specifies procedures for inspecting the rotor hub-shaft and depending on the results of the inspection, replacing any rotor hub-shaft that has cracks or suspicion of cracks, and reporting the results of the inspection to Airbus Helicopters. EASA Emergency AD 2026-0078-E also prohibits installing any affected rotor hub-shaft that has not passed an inspection on any helicopter.

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 (CAA) 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 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.

AD Requirements

This AD requires accomplishing the actions specified in EASA Emergency AD 2026-0078-E, described previously, as incorporated by reference, except for any differences identified as exceptions in the regulatory text of this AD. See “Differences Between this AD and the MCAI,” for a detailed description of the differences.

Differences Between This AD and the MCAI

The MCAI applies to MBB-BK117 D-3m helicopters, whereas this AD does not because that model does not have an FAA type certificate.

Explanation of Required Compliance Information

In the FAA's ongoing efforts to improve the efficiency of the AD process, the FAA developed a process to use some CAA ADs as the primary source of information for compliance with requirements for corresponding FAA ADs. The FAA has been coordinating this process with ( printed page 22997) manufacturers and CAAs. As a result, EASA Emergency AD 2026-0078-E is incorporated by reference in this AD. This AD requires compliance with EASA Emergency AD 2026-0078-E in its entirety through that incorporation, except for any differences identified as exceptions in the regulatory text of this AD. Using common terms that are the same as the heading of a particular section in EASA Emergency AD 2026-0078-E does not mean that operators need comply only with that section. For example, where EASA Emergency AD 2026-0078-E refers to “all required actions and compliance times,” compliance with this AD requirement is not limited to the section titled “Required Action(s) and Compliance Time(s)” in EASA Emergency AD 2026-0078-E. Material required by EASA Emergency AD 2026-0078-E for compliance will be available at regulations.gov under Docket No. FAA-2026-3867 after this AD is published.

Justification for Immediate Adoption and Determination of the Effective Date

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.

An unsafe condition exists that required the immediate adoption of Emergency AD 2026-08-51, issued on April 16, 2026, to all known U.S. owners and operators of these helicopters. The FAA found that the risk to the flying public justified forgoing notice and comment prior to adoption of this rule because a number of helicopters that have the affected part installed require immediate action. 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 forego notice and comment.

Regulatory Flexibility Act

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 FAA has determined that it has good cause to adopt this rule without prior notice and comment, RFA analysis is not required.

Interim Action

The FAA considers that this AD is an interim action. If final action is later identified, the FAA might consider additional rulemaking.

Costs of Compliance

The FAA estimates that this AD affects 78 helicopters of U.S. registry.

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

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

Paperwork Reduction Act

A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a currently valid OMB Control Number. The OMB Control Number for this information collection is 2120-0056. Public reporting for this collection of information is estimated to be approximately 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. All responses to this collection of information are mandatory. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to: Information Collection Clearance Officer, Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177-1524.

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. ( printed page 22998)

Regulatory Findings

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.

The Amendment

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:

Authority: 49 U.S.C. 106(g), 40113, 44701.

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

2026-08-51 Airbus Helicopters Deutschland GmbH (AHD): Amendment 39-23249; Docket No. FAA-2026-3867; Project Identifier MCAI-2026-00403-R.

(a) Effective Date

The FAA issued Emergency Airworthiness Directive (AD) 2026-08-51 on April 16, 2026 (also referred to as the emergency AD), directly to affected owners and operators. As a result of such actual notice, the emergency AD was effective for those owners and operators on the date it was received. This AD contains the same requirements as the emergency AD and, for those who did not receive actual notice, is effective on May 14, 2026.

(b) Affected ADs

None.

(c) Applicability

This AD applies to all Airbus Helicopters Deutschland GmbH (AHD) Model MBB-BK 117 D-3 helicopters, certificated in any category.

(d) Subject

Joint Aircraft Service Component (JASC) Code: 6300, Main rotor drive system.

(e) Unsafe Condition

This AD was prompted by a report of a crack on the affected part, which was detected after the crew reported increased vibration of the helicopter. The mandatory continuing airworthiness information defines the affected part as a rotor hub-shaft manufacturer part number D623M1501203 and D623M1501204. The FAA is issuing this AD to address cracking of the rotor hub-shaft, which could lead to failure of the main rotor transmission and consequent loss of control of the helicopter.

(f) Compliance

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

(g) Required Actions

Except as specified in paragraph (h) of this AD: Comply with all required actions and compliance times specified in, and in accordance with European Union Aviation Safety Agency Emergency AD 2026-0078-E, dated April 13, 2026 (EASA Emergency AD 2026-0078-E).

(h) Exceptions to EASA Emergency AD 2026-0078-E

(1) Where EASA Emergency AD 2026-0078-E refers to its effective date, this AD requires using the effective date of this AD.

(2) Where EASA Emergency AD 2026-0078-E requires compliance in terms of flight hours, this AD requires using hours time-in-service.

(3) This AD does not adopt the “Remarks” section of EASA Emergency AD 2026-0078-E.

(i) Special Flight Permits

Special flight permits, as described in 14 CFR 21.197 and 21.199, are not allowed.

(j) 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 (k) of this AD and email 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.

(k) Additional Information

For more information about this AD, contact David Enns, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (316) 946-4147; email: david.enns@faa.gov.

(l) 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) European Union Aviation Safety Agency (EASA) Emergency AD 2026-0078-E, dated April 13, 2026.

(ii) [Reserved]

(3) For EASA material identified in this AD, contact EASA, Konrad-Adenauer-Ufer 3, 50668 Cologne, Germany; phone: +49 221 8999 000; email: ADs@easa.europa.eu; website: easa.europa.eu. You may find the EASA material on the EASA website at ad.easa.europa.eu.

(4) You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 10101 Hillwood Parkway, Fort Worth, TX 76177. 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 22995