# [Amended]
**AGENCY:**
Federal Aviation Administration (FAA), DOT.
**ACTION:**
Notice of proposed rulemaking (NPRM).
**SUMMARY:**
The FAA proposes to supersede Airworthiness Directive (AD) 2020-09-15, which applies to certain Airbus Helicopters Model AS332C, AS332C1, AS332L, and AS332L1 helicopters. AD 2020-09-15 requires removing the removable parts of the dual hoist installation or removing the de-icing system and allows, for certain helicopters, revising the rotorcraft flight manual (RFM) for the helicopter and installing a placard as an optional method of compliance. Since the FAA issued AD 2020-09-15, analysis revealed that additional vibration level measurements are necessary. This proposed AD would retain all the requirements of AD 2020-09-15 and would require for certain helicopters repetitively measuring vibration levels in-flight, and depending on the results, performing corrective actions. The FAA is proposing this AD to address the unsafe condition on these products.
**DATES:**
The FAA must receive comments on this NPRM by February 2, 2026.
**ADDRESSES:**
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-2025-5389; 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 NPRM, 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 Airbus Helicopters material identified in this AD, contact Airbus Helicopters, 2701 North Forum Drive, Grand Prairie, TX 75052; phone: (972) 641-0000 or (800) 232-0323; fax: (972) 641-3775; or at *airbus.com/en/products-services/helicopters/hcare-services/airbusworld.*
• 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. It is also available at *regulations.gov* under Docket No. FAA-2025-5389.
**FOR FURTHER INFORMATION CONTACT:**
Matthew Williams, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (316) 946-4134; email: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
**Comments Invited**
The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the *ADDRESSES* section. Include “Docket No. FAA-2025-5389; Project Identifier MCAI-2024-00716-R” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, 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 the proposal 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 NPRM.
**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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to Matthew Williams, 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 AD 2020-09-15, Amendment 39-19911 (85 FR 30589, May 20, 2020) (AD 2020-09-15), for Airbus Helicopters Model AS332C, AS332C1, AS332L, and AS332L1 helicopters equipped with a dual hoist installation and de-icing system, except those that have Airbus Helicopters modification 0722907 installed in production. AD 2020-09-15 was prompted by an MCAI originated by the European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union. EASA issued AD 2018-0142R1, dated December 9, 2019 (EASA AD 2018-0142R1) to address vibrations around the 12Hz frequency. EASA AD 2018-0142R1 states that during the first flight of an Airbus Helicopters Model AS332L helicopter after a retrofit that re-installed the deicing system, vibrations around the 12Hz frequency were observed. Subsequent flight tests and analysis determined that this vibration is due to the specific helicopter configuration. Factors that contributed to the vibration included simultaneous installation of riveted main frames X3855 and X5295 (pre-Airbus Helicopter modification 0722907), additional weight created by parts of the rotor de-icing system on the main rotor head (the distributor and de-icing harnesses), and removable parts (hoist arm and hoists) of the dual hoist installation.
AD 2020-09-15 requires removing the removable parts of the dual hoist installation or removing the de-icing system, and allows, for certain helicopters, revising the RFM for the helicopter and installing a placard as an optional method of compliance. The FAA issued AD 2020-09-15 to address vibrations around the 12Hz frequency. The unsafe condition, if not addressed, could generate divergent aeromechanic coupling between the helicopter structure and the rotor, possibly resulting in mechanical failure of structural parts and loss of control of the helicopter.
**Actions Since AD 2020-09-15 Was Issued**
Since the FAA issued AD 2020-09-15, EASA issued EASA AD 2024-0100, dated May 10, 2024 (EASA AD 2024-0100), which superseded EASA AD 2018-0142R1. EASA AD 2024-0100 stated that the same occurrence of the 12Hz vibratory condition was reported on a helicopter with Airbus Helicopters modification 0722907 embodied and that it was necessary for all helicopters with this modification to measure vibrations in-flight, interpret the results, and depending on the results, send the vibration levels to Airbus Helicopters or modify the helicopter configuration.
After EASA issued EASA AD 2024-0100, EASA superseded EASA AD 2024-0100 and issued EASA AD 2024-0233, dated December 5, 2024 (EASA AD 2024-0233) (also referred to as the MCAI). The MCAI states that since EASA AD 2024-0100 was issued, it was determined that further vibration level measurements were necessary after performing certain maintenance tasks. The MCAI further states that EASA AD 2024-0233 is considered to be an interim action.
This condition, if not addressed, could generate divergent aeromechanic coupling between the helicopter structure and the rotor, possibly resulting in mechanical failure of structural parts and loss of control of the helicopter.
You may examine the MCAI in the AD docket at *regulations.gov* under Docket No. FAA-2025-5389.
**Material Incorporated by Reference Under 1 CFR Part 51**
The FAA reviewed Airbus Helicopters Alert Service Bulletin AS332-04-00-0001 Issue 002, dated December 4, 2024 (ASB AS332-04-00-0001), which specifies procedures for installing the accelerometer in the cockpit of the helicopter, repetitively inspecting the vibration level at 12 Hz each time a specific maintenance task is completed, and interpreting the results. Depending on the results of this inspection, ASB AS332-04-00-0001 specifies procedures for corrective actions, which include changing the configuration by either removing the dual hoist system or removing the de-icing harness and contacting Airbus Helicopters for further instructions.
This proposed AD would also require Airbus Helicopters Emergency Alert Service Bulletin (EASB) No. 01.00.91 Revision 1 (EASB 01.00.91 Rev 1) for Model AS332C, and AS332C1 helicopters, and EASB No. 01.00.96 Revision 0 (EASB 01.00.96) for Model AS332L and AS332L1 helicopters, both dated December 4, 2019. EASB 01.00.91 Rev 1 specifies procedures for removing parts of the dual hoist installation or removing the de-icing system. EASB 01.00.96 describes procedures for amending the RFM of Airbus Helicopters Model AS332L and AS332L1 helicopters to limit the flight envelope and the Vne and installing a placard. EASB 01.00.96 also describes procedures for removing parts of the dual hoist installation or removing the de-icing system. The Director of the Federal Register approved EASB 01.00.91 Rev 1 and EASB 01.00.96 for incorporation by reference as of May 20, 2020 (85 FR 30589, May 20, 2020).
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 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, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.
**Proposed AD Requirements in This NPRM**
This proposed AD would retain all the requirements of AD 2020-09-15 and would require repetitively measuring the vibration level, interpreting the results, and depending on the results, removing certain parts and further inspections. This proposed AD would also allow an alternative to removing parts by placing a placard and revising the RFM for the helicopter.
Measuring the vibration levels in-flight and revising the existing RFM for the helicopter may be performed by the owner/operator (pilot) holding at least a private pilot certificate and must be entered into the aircraft records showing compliance with this action in accordance with 14 CFR 43.9(a) and 91.417(a)(2)(v). The pilot may perform these actions because they only involve recording data in-flight and revising the existing RFM by inserting pages, which are not considered maintenance actions. This proposed AD would also prohibit installing the de-icing system and the dual hoist unless certain requirements are accomplished.
**Interim Action**
The FAA considers that this proposed AD would be an interim action. If final action is later identified, the FAA might consider further rulemaking.
**Costs of Compliance**
The FAA estimates that this AD, if adopted as proposed, would affect five helicopters of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD.
| Action | Labor cost | Parts cost | Cost per product | Cost on U.S. |
| --- | --- | --- | --- | --- |
| Remove the removable parts of the dual hoist | 12 work-hours × $85 per hour = $1,020 per helicopter | $0 | $1,020 | $5,100 |
| Remove the de-icing system | 12 work-hours × $85 per hour = $1,020 per helicopter | 0 | $1,020 | 5,100 |
| Measure vibrations to include interpreting results | 7 work-hours × $85 per hour = $595 | 0 | $595 per cycle | 2,975 |
The FAA estimates the following costs to do any repairs/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 repairs or replacements:
| Action | Labor cost | Parts cost | Cost per product |
| --- | --- | --- | --- |
| Revise the RFM | 1 work-hour × $85 per hour = $85 | $0 | $85 |
| Install a placard | 1 work-hour × $85 per hour = $85 | 0 | 85 |
**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**
The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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 the proposed regulation:
(1) Is not a “significant regulatory action” under Executive Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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 Proposed Amendment**
Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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
2. The FAA amends § 39.13 by:
a. Removing Airworthiness Directive 2020-09-15, Amendment 39-19911 (85 FR 30589, May 20, 2020); and
b. Adding the following new airworthiness directive:
*Airbus Helicopters:* Docket No. FAA-2025-5389; Project Identifier MCAI-2024-00716-R.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by February 2, 2026.
**(b) Affected ADs**
This AD replaces AD 2020-09-15, Amendment 39-19911 (85 FR 30589, May 20, 2020).
**(c) Applicability**
This AD applies to Airbus Helicopters Model AS332C, AS332C1, AS332L, and AS332L1 helicopters, certificated in any category, equipped with a dual hoist installation and de-icing system.
**(d) Subject**
Joint Aircraft System Component (JASC) Code 1810, Helicopter vibration analysis.
**(e) Unsafe Condition**
This AD was prompted by a report of vibrations around the 12 Hz frequency due to the specific helicopter configuration and determination that additional vibration level measurements are necessary. The FAA is issuing this AD to prevent divergent aeromechanic coupling between the helicopter structure and rotor. The unsafe condition, if not addressed, could result in mechanical failure of structural parts 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**
(1) For helicopters without Airbus Helicopters modification 0722907 installed, within 7 days after May 20, 2020 (the effective date of AD 2020-09-15): Remove the removable parts of the dual hoist installation or remove the de-icing system in accordance with the instructions of section 3.B of Airbus Helicopters Emergency Alert Service Bulletin (EASB) AS332 01.00.91, Revision 1, dated December 4, 2019 (EASB AS32 01.00.91 Rev 1), or Section 3.B.2 of Airbus Helicopters EASB AS332 01.00.96, Revision 0, dated December 4, 2019 (EASB AS332 01.00.96), as applicable to the helicopter, except you are not required to contact Airbus Helicopters.
(2) For helicopters with Airbus Helicopters modification 0722907 installed, within 110 hours time-in-service (TIS) or 30 days whichever occurs first after the effective date of this AD and thereafter, during the first flight after each time any of the maintenance tasks identified in the COMPLIANCE: MANDATORY section of Airbus Helicopters Alert Service Bulletin (ASB) AS332-04-00-0001 Issue 002, dated December 4, 2024 (ASB AS332-04-00-0001) is accomplished, perform a vibration level measurement.
(i) With the accelerometer already installed, check the measurement of the vibration level in-flight, at 12 Hz by following figure 1 to paragraph (g)(2)(i) of this AD. The owner/operator (pilot) holding at least a private pilot certificate may perform this check and must enter compliance with these paragraphs into 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 135.439.
**Figure 1 to Paragraph (g)(2)(i)—Method of Measurement**
(ii) Interpret the results in accordance with the instructions in Section 4.4 of ASB AS332-04-00-0001 except you are not required to send any information to Airbus Helicopters. If the vibration level between 11.7 Hz and 12.7 Hz is more than 0.08g (0.40 IPS), before further flight, revise the helicopter configuration by removing the dual hoist system or removing the blade de-icing harnesses in accordance with instructions of section 4.5 through 4.5.2.1 of ASB AS332-04-00-0001.
**(h) Optional Method of Compliance**
For helicopters without Airbus Helicopters modification 0722907 installed: Revising the rotorcraft flight manual for your helicopter by inserting the information specified in Appendix 4A, 4B, or 4C of EASB AS332 01-00.96, as applicable to your helicopter model and configuration, and installing a locally made placard on the instrument panel, in accordance with the instructions of section 3.B.1 of EASB AS332 01-00.96, is an acceptable method for compliance with the requirements of paragraph (g)(1) of this AD.
**(i) 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 responsible Flight Standards 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 (j) of this AD and email to: *[email protected].*
(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office.
**(j) Additional Information**
For more information about this AD, contact Matthew Williams, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (316) 946-4134; email: *[email protected].*
**(k) 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 [DATE 35 DAYS AFTER PUBLICATION OF THE FINAL RULE].
(i) Airbus Helicopters Alert Service Bulletin AS332-04-00-0001 Issue 002, dated December 4, 2024.
(ii) [Reserved]
(4) The following material was approved for IBR on May 20, 2020, (85 FR 30589, May 20, 2020).
(i) Airbus Helicopters Emergency Alert Service Bulletin No. 01.00.91 Revision 1, dated December 4, 2019.
(ii) Airbus Helicopters Emergency Alert Service Bulletin No. 01.00.96 Revision 0, dated December 4, 2019.
(5) For Airbus material identified in this AD, contact Airbus Helicopters, 2701 North Forum Drive, Grand Prairie, TX 75052; phone: (972) 641-0000 or (800) 232-0323; fax: (972) 641-3775; or at *airbus.com/en/products-services/helicopters/hcare-services/airbusworld.*
(6) 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.
(7) 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 *[email protected].*
Issued on December 12, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.