Background The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to Airbus Helicopters Deutschland GmbH Model EC135P1, EC135P2, EC135P2+, EC135P3, EC135T1, EC135T2, EC135T2+, EC135T3, EC635T2+, MBB-BK 117 C-2, MBB-BK 117 D-2, and MBB-BK 117 D-3 helicopters. The NPRM was published in the Federal Register on April 25, 2025 (90 FR 17348). The NPRM was prompted by EASA AD 2023-0066, dated March 24, 2023 (EASA AD 2023-0066) (also referred to as the MCAI), issued by EASA, which is the Technical Agent for the Member States of the European Union. The MCAI states that due to a review of design data, it was determined that hoist boom assemblies, part number (P/N) 44301-500, 44307-500, and 44307-500-1, must be inspected repetitively based on accumulated cycles. The additional inspection criteria were due to a new fatigue calculation to factor in external load, particularly human external cargo. In the NPRM, the FAA proposed to require determining the total cycles of certain hoist boom assemblies, inspecting those hoist boom assemblies, and depending on the results, taking corrective action. The FAA is issuing this AD to prevent failure of the hoist boom assembly. The unsafe condition, if not addressed, could lead to in-flight loss of the hoist load and consequent injury to occupants. You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2025-0630. Discussion of Final Airworthiness Directive Comments The FAA received one comment from Air Evac Lifeteam. The following presents the comment received on the NPRM and the FAA's response to the comment. Air Evac Lifeteam commented that the proposed AD lacks a compliance path for aircraft that do not have the affected part installed and requested the FAA revise the Applicability paragraph of the proposed AD to specify aircraft with the affected part installed. Air Evac Lifeteam alternatively suggested that the FAA add a compliance requirement for aircraft that do not have the affected part installed (Group 2 helicopters) that states that no further action is required. The applicability statement in each AD action identifies all aircraft affected by that AD. All of the requirements of an AD apply to the aircraft listed in the applicability, unless a specific paragraph in the AD specifies that it applies only to certain aircraft, such as those with an affected part installed. The MCAI that this AD incorporates by reference includes an installation limitation that currently applies to all models listed in the Applicability paragraph of this AD. If the Applicability paragraph of this AD were revised to apply only to those aircraft with the affected part installed, the installation limitation would only apply to aircraft with the affected part installed, rather than all aircraft. The FAA did not change this AD as a result of this comment. 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 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, 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 EASA AD 2023-0066, which specifies procedures for inspecting certain part-numbered hoist boom assemblies at certain intervals and, depending on the results, replacing or removing certain parts or taking further corrective action to resolve the discrepancy [crack, deformation, dent, corrosion, or other damage] or replacing the hoist boom assembly. EASA AD 2023-0066 also provides a terminating action for the inspections and prohibits installing those part-numbered hoist boom assemblies on any helicopter unless its requirements are met. 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. Differences Between This AD and the MCAI The MCAI applies to Model EC635 P2+, EC635 P3, EC635 T1, EC635 T3, and MBB-BK117 D-3m helicopters, whereas this AD does not because these model helicopters do not have an FAA type certificate. The MCAI requires accomplishing a corrective action in accordance with the instructions of the service material, whereas this AD requires repairing or replacing affected parts that have certain discrepancies, within allowable limits, as described in this AD. Costs of Compliance The FAA estimates that this AD affects 732 helicopters of U.S. registry. Labor rates are estimated at $85 per hour. Based on these numbers, the FAA estimates the following costs to comply with this AD. If required, determining the total cycles will take 0.5 work-hour for an estimated cost of $43 per helicopter. Inspecting a hoist boom assembly will take 4 work-hours for an estimated cost of $340 per helicopter and $248,880 for the U.S. fleet, per inspection cycle. Repairing any surface deformation, damage, or corrosion that is within allowable limits will take up to 1 work-hour and parts will cost a nominal amount for an estimated cost of up to $85 per helicopter. Replacing a hoist boom assembly (which includes a boom elbow, boom tube, and boom adapter) will take up to 5 work-hours (depending on configuration) and parts will cost up to $88,812 (depending on P/N) for an estimated cost of up to $89,237 per helicopter. 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 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 adding the following new airworthiness directive: 2025-18-04 Airbus Helicopters Deutschland GmbH: Amendment 39-23131; Docket No. FAA-2025-0630; Project Identifier MCAI-2023-00518-R. (a) Effective Date This airworthiness directive (AD) is effective October 21, 2025. (b) Affected ADs None. (c) Applicability This AD applies to Airbus Helicopters Deutschland GmbH Model EC135P1, EC135P2, EC135P2+, EC135P3, EC135T1, EC135T2, EC135T2+, EC135T3, EC635T2+, MBB-BK 117 C-2, MBB-BK 117 D-2, and MBB-BK 117 D-3 helicopters, certificated in any category. Note 1 to paragraph (c): Helicopters with an EC135P3H designation are Model EC135P3 helicopters, helicopters with an EC135T3H designation are Model EC135T3 helicopters, and helicopters with an MBB-BK 117C-2e designation are Model MBB-BK 117C-2 helicopters. (d) Subject Joint Aircraft System Component (JASC) Code: 2500, Cabin Equipment/Furnishings. (e) Unsafe Condition This AD was prompted by a review of design data and the determination for a new calculation of accumulated hoist boom cycles (cycles) to factor in external load and repetitive inspections. The FAA is issuing this AD to prevent failure of the hoist boom assembly. The unsafe condition, if not addressed, could lead to in-flight loss of the hoist load and consequent injury to occupants. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Requirements Except as specified in paragraphs (h) and (i) of this AD: Comply with all required actions and compliance times specified in, and in accordance with, European Union Aviation Safety Agency AD 2023-0066, dated March 24, 2023 (EASA AD 2023-0066). (h) Exceptions to EASA AD 2023-0066 (1) Where EASA AD 2023-0066 refers to its effective date, this AD requires using the effective date of this AD. (2) Where paragraphs (3) and (4) of EASA AD 2023-0066 refer to any discrepancy, for the purposes of this AD, a discrepancy is identified as surface deformation, damage, or corrosion that is within allowable limits. (3) Where paragraph (3) of EASA AD 2023-0066 specifies "before next hoist operation, accomplish the applicable corrective action in accordance with the instructions of the ASB", this AD requires replacing that text with "before next hoist operation, repair any deformation, damage, and corrosion that is within the allowable limit, apply a protective chemical film, and restore the protective finish. If the inspection criteria fails (if there is surface deformation, damage, or corrosion that exceeds the allowable limit, any damage or corrosion in a riveted bore hole, or any crack), before further flight, replace the hoist boom assembly (which includes the support assembly) with a serviceable part, as defined in EASA AD 2023-0066". (4) This AD does not adopt the "Remarks" section of EASA AD 2023-0066. (i) No Reporting Requirement Although the material referenced in EASA AD 2023-0066 specifies to submit certain information to the manufacturer, this AD does not require that action. (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 Steven Warwick, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (817) 222-5225; email: steven.r.warwick@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) AD 2023-0066, dated March 24, 2023. (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 this material on the EASA website at ad.easa.europa.eu . (4) You may view this material at the FAA, Office of the Regional Counsel, Southwest Region, 10101 Hillwood Parkway, Room 6N-321, 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. Issued on September 3, 2025. Steven W. Thompson, Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.