SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2025-06-04, Amendment 39-22992 (90 FR 14723, April 4, 2025), (AD 2025-06-04). AD 2025-06-04 applied to all Airbus Helicopters Model AS350B, AS350B1, AS350B2, AS350B3, AS350BA, AS350D, AS355E, AS355F, AS355F1, AS355F2, AS355N, AS355NP, EC130B4, and EC130T2 helicopters. The NPRM was published in the Federal Register on November 25, 2025 (90 FR 53238). The NPRM was prompted by EASA AD 2023-0044, dated February 28, 2023 (EASA AD 2023-0044) (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 after a fleet design review for detection of particles in the MGB, it was determined that additional maintenance actions are necessary to improve detection of particles in MGB that have certain part-numbered planet gear bearings installed.

In the NPRM, the FAA proposed to continue to require the actions of AD 2025-06-04 and revise the interval compliance times. The FAA is issuing this AD to detect and correct particles in the MGB. The unsafe condition, if not addressed, could result in reduced or loss of control of the helicopter.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from two commenters. The commenters were Airbus Helicopters and an anonymous individual. The individual did not request any changes to the AD, therefore the FAA infers that the commenter supported the NPRM. Airbus Helicopters requested that the FAA require periodic inspections and requested revision to the interval compliance times.” The following presents the comments received on the NPRM and the FAA's response to each comment.

Request for Borescope Bevel Wheel Inspection

Airbus Helicopters requested that the proposed AD be revised to require a periodic borescope inspection of the bevel wheel without condition. Airbus Helicopters stated that the proposed AD only requires a borescope bevel wheel inspection in case of particles found on MGB magnetic plugs during a visual inspection, and this does not address the unsafe condition.

The FAA infers that Airbus Helicopters requested that the periodic borescope bevel wheel inspections be required at defined compliance times, without any conditions in accordance with the Airbus material. The proposed AD already adopts paragraph (1) of EASA AD 2023-0044, which requires accomplishing repetitive borescope inspections of the bevel wheel of the affected MGB in accordance with the instructions of the material. Therefore, there is no change made to this AD based on this request.

Request for Correction of the Compliance Times

Airbus Helicopters stated the interval compliance times listed in Table 1 to paragraph (h)(6)(i) of the proposed AD (150 hours time-in-service (TIS) for EC130T2 and 100 hours TIS for all other versions) are not in accordance with published maintenance documents, including the Airworthiness Limitations Section, the Master Servicing Manual, the Aircraft Maintenance Manual (AMM), or the Maintenance Manual.

The exception in paragraph (h)(6) of the proposed AD was intended to address the compliance times of the AMM tasks and not change the inspection requirement. After further review the FAA has determined this exception, which includes Table 1 to paragraph (h)(6)(i), is no longer necessary due to the FAA incorporating the MCAI compliance times. Accordingly, the final rule has been updated with the deletion of this exception and table.

Conclusion

The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting the AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, and any other changes described previously, 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

This AD requires EASA AD 2023-0044, which the Director of the Federal Register approved for incorporation by reference as of May 9, 2025 (90 FR 14723, April 4, 2025). EASA AD 2023-0044 specifies procedures for performing repetitive borescope visual inspections of the bevel wheel of the affected MGB for particles, collecting and analyzing any particles detected, and depending on the results, accomplishing further actions, accomplishing corrective action in accordance with the ASB, or contacting AH [Airbus Helicopters] for further corrective action. EASA AD 2023-0044 also specifies procedures for accomplishing a borescope visual inspection of the bevel wheel of the ( printed page 34748) affected MGB for particles following the detection of any particles at the MGB magnetic plug during accomplishment of certain maintenance tasks and depending on the results, taking corrective action. EASA AD 2023-0044 also prohibits installing an affected MGB on any helicopter unless certain 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 AS350BB helicopters, whereas this AD does not because that model does not have an FAA type certificate.

Where Note 1 in the material referenced in the MCAI specifies the option of 1 mechanical technician and 1 crew member, for this AD, the pilot is only permitted to turn the tail rotor (b) because the other actions specified in the note must be accomplished by persons authorized under 14 CFR 43.3. Therefore, for the purposes of this AD, the owner/operator (pilot) may turn the tail rotor (b) and must enter compliance with the applicable paragraph of this AD in the helicopter maintenance records in accordance with 14 CFR 43.9(a) and 91.417(a)(2)(v). The pilot may perform this action because it only involves turning the tail rotor (b). This action can be performed equally well by a pilot or a mechanic. This action is an exception to the FAA's standard maintenance regulations.

Where the material referenced in the MCAI specifies contacting Airbus Helicopters for a certain action, this AD requires accomplishing action in accordance with a method approved by the FAA, EASA, or Airbus Helicopters' EASA Design Organization Approval.

Costs of Compliance

The FAA estimates that this AD affects 522 helicopters of U.S. registry.

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

The new requirements of this AD add no additional economic burden.

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

Certain corrective action could vary significantly from helicopter to helicopter. The FAA has no data to determine the costs to accomplish the corrective action.

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.

The Amendment

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

( printed page 34749) Authority: 49 U.S.C. 106(g), 40113, 44701.

2. The FAA amends § 39.13 by:

a. Removing Airworthiness Directive 2025-06-04, Amendment 39-22992 ( 90 FR 14723, April 4, 2025); and

b. Adding the following new airworthiness directive:

2026-12-03 Airbus Helicopters: Amendment 39-23373; Docket No. FAA-2025-5032; Project Identifier AD-2025-01042-R.

(a) Effective Date

This airworthiness directive (AD) is effective July 14, 2026.

(b) Affected ADs

This AD replaces AD 2025-06-04, Amendment 39-22992 (90 FR 14723, April 4, 2025) (AD 2025-06-04).

(c) Applicability

This AD applies to all Airbus Helicopters Model AS350B, AS350B1, AS350B2, AS350B3, AS350BA, AS350D, AS355E, AS355F, AS355F1, AS355F2, AS355N, AS355NP, EC130B4, and EC130T2 helicopters, certificated in any category.

(d) Subject

Joint Aircraft System Component (JASC) Code 6320, Main rotor gearbox.

(e) Unsafe Condition

This AD was prompted by an assessment performed by the manufacturer which revealed that additional maintenance actions are necessary to improve detection of particles in the main gearbox (MGB) with certain part-numbered planet gear bearings installed. The FAA is issuing this AD to detect and correct particles in the MGB. The unsafe condition, if not addressed, could result in reduced or 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 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 2023-0044, dated February 28, 2023 (EASA AD 2023-0044).

(h) Exceptions to EASA AD 2023-0044

(1) Where EASA AD 2023-0044 defines “serviceable MGB” as “An affected MGB which has accumulated less than 330 flight hours (FH) since new (first installation on a helicopter), or since an overhaul, or since an inspection in accordance with the instructions of the ASB”, this AD requires replacing that text with “An affected MGB which has accumulated less than 330 total hours time-in-service (TIS) since new (zero total hours TIS), since last overhaul if an overhaul has been accomplished, or since last inspection and any specified corrective action in accordance with the instructions of the ASB if an inspection and any specified corrective action by following the instructions of the ASB have been accomplished”.

(2) Where EASA AD 2023-0044 requires compliance in terms of flight hours, this AD requires using hours TIS.

(3) Where EASA AD 2023-0044 refers to its effective date, this AD requires using May 9, 2025 (the effective date of AD 2025-06-04).

(4) Where Note 1 in the material referenced in paragraph (1) of EASA AD 2023-0044 specifies the option of 1 mechanical technician and 1 crew member, for this AD, the pilot is only permitted to turn the tail rotor (b). The owner/operator (pilot) holding at least a private pilot certificate may turn the tail rotor (b) and must enter compliance with paragraph (g) of this AD in the helicopter maintenance records in accordance with 14 CFR 43.9(a) and 91.417(a)(2)(v). The record must be maintained as required by 14 CFR 91.417, 121.380, or 135.43. All other actions specified in Note 1 in the material referenced in paragraph (1) of EASA AD 2023-0044 must be accomplished by persons authorized under 14 CFR 43.3.

(5) Where Note 2 in the material referenced in paragraph (1) of EASA AD 2023-0044 specifies contacting Airbus Helicopters [AH] for further instructions if the bottom of the radius (a6) of the bevel wheel (a3) or head screws (a4) (see Figure 2) are not clearly visible, this AD requires, before further flight, accomplishing action in accordance with a method approved by the FAA, EASA, or Airbus Helicopters' EASA Design Organization Approval (DOA). If approved by the DOA, the approval must include the DOA-authorized signature.

(6) Where the material referenced in paragraph (3) of EASA AD 2023-0044 specifies performing a metallurgical analysis and contacting Airbus Helicopters if collected particles cannot be characterized with Work Card 20-08-01-601, this AD does not require contacting Airbus Helicopters but does require performing the metallurgical analysis.

(7) Where the material referenced in paragraph (3) of EASA AD 2023-0044 contains a special flight permit provision, this AD does not allow that provision but instead requires the special flight permit limitations in paragraph (j) of this AD.

(8) Where the material referenced in paragraph (3) of EASA AD 2023-0044 specifies contacting Airbus Helicopters if the damaged module cannot be identified, this AD requires, before further flight, accomplishing action in accordance with a method approved by the FAA, EASA, or Airbus Helicopters' EASA DOA. If approved by the DOA, the approval must include the DOA-authorized signature.

(9) Where paragraph (5) of EASA AD 2023-0044 states “to contact AH for corrective action(s) instructions, and within the compliance time specified therein, to accomplish those instructions accordingly”, this AD requires replacing that text with “accomplishing corrective actions in accordance with a method approved by the FAA, EASA, or Airbus Helicopters' EASA DOA. If approved by the DOA, the approval must include the DOA-authorized signature”.

(10) Where paragraph (7) of EASA AD 2023-0044 states “since new (first installation on a helicopter), or since an overhaul, or since an inspection in accordance with the instructions of the ASB, as applicable, and, thereafter, as required by this AD”, this AD requires replacing that text with “since new (zero total hours time-in-service), or since last overhaul if an overhaul has been accomplished, or since last inspection and any specified corrective action in accordance with the instructions of the ASB if an inspection and any specified corrective action by following the instructions of the ASB have been accomplished, and thereafter as required by this AD”.

(11) This AD does not adopt the “Remarks” section of EASA AD 2023-0044.

(i) No Reporting Requirement

Although the material referenced in EASA AD 2023-0044 specifies to submit certain information to the manufacturer, this AD does not require that action.

(j) Special Flight Permit

A special flight permit may be issued in accordance with 14 CFR 21.197 and 21.199 to permit a one-time, non-revenue flight to a location where the actions required by this AD can be accomplished. This flight must be performed with only essential flight crew.

(k) 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 (l) 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.

(l) Additional Information

For more information about this AD, contact Luna Yang, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (847) 294-7380; email: luna.y.yang@faa.gov.

(m) 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 May 9, 2025 (90 FR 14723, April 4, 2025).

(i) European Union Aviation Safety Agency (EASA) AD 2023-0044, dated February 28, 2023.

(ii) [Reserved] ( printed page 34750)

(4) 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.

(5) 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.

(6) 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 34746