2025-20-10: Tail Rotor System

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: a. Removing Airworthiness Directive 2021-26-07, Amendment 39-21866 (86 FR 72829, December 23, 2021); and b. Adding the following new airworthiness directive: 2025-20-10 Airbus Helicopters: Amendment 39-23163; Docket No. FAA-2025-0922; Project Identifier MCAI-2024-00650-R. (a) Effective Date This airworthiness directive (AD) is effective December 30, 2025. (b) Affected ADs This AD replaces AD 2021-26-07, Amendment 39-21866 (86 FR 72829, December 23, 2021). (c) Applicability This AD applies to Airbus Helicopters Model EC120B helicopters, certificated in any category. (d) Subject Joint Aircraft System Component (JASC) Code 6422, Tail Rotor System. (e) Unsafe Condition This AD was prompted by analysis of recurrent loss of tightening torque on several attachment bolts on the tail rotor (TR) hub body. The FAA is issuing this AD to detect cracking and fretting of the TR hub body. The unsafe condition, if not addressed, could lead to loss of the TR drive, and consequent loss of yaw control of the helicopter. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Required Actions (1) Within 15 hours time-in-service (TIS) or 7 days, whichever occurs first after the effective date of this AD, and thereafter at intervals not to exceed 15 hours TIS, using a light source and mirror, visually inspect TR hub body part number (P/N) C642A0100103 for a crack in the entire inspection area depicted in Figure 1 of Airbus Helicopters Emergency Alert Service Bulletin 05A020 Revision 3, dated September 19, 2024. If any crack is found, before further flight, perform the actions in paragraphs (g)(1)(i) and (ii) of this AD. (i) Remove the TR hub body and each bolt, washer, and nut installed on the TR hub body from service and replace with airworthy parts. (ii) Inspect the TR splined flange for corrosion, impacts, fretting, wear, and a crack in the areas identified in Figure 2 to paragraph (g)(1)(ii) of this AD. If the condition of the part (including corrosion, impacts, fretting, wear, or cracks) exceeds the criteria as specified in Figure 1 to paragraph (g)(1)(ii) of this AD, before further flight, remove the splined flange from service and replace with an airworthy part. Note 1 to paragraph (g)(1)(ii): You may refer to "Detailed Check-Splined Flange," Task 64-21-00, 6-5, Airbus Aircraft Maintenance Manual (AMM), dated October 15, 2020, which pertains to the TR splined flange inspection. Figure 1 to paragraph (g)(1)(ii)-Inspection Criteria for TR Splined Flange ER25NO25.300 Figure 2 to paragraph (g)(1)(ii)-Inpsection Area of Tail Rotor Splined Flange ER25NO25.301 (2) For helicopters with 9,000 or more total hours TIS or with unknown total hours TIS, within 15 hours TIS or 7 days, whichever occurs first after the effective date of this AD, and thereafter at intervals not to exceed 1,000 hours TIS, remove each bolt washer, and nut installed on the TR hub body from service and replace with airworthy parts and perform the actions in paragraph (g)(1)(ii) of this AD. (3) For helicopters with less than 9,000 total hours TIS, within 1,000 hours TIS or before accumulating 9,000 total hours TIS, whichever occurs first after the effective date of this AD, and thereafter at intervals not to exceed 1,000 hours TIS, remove each bolt, washer, and nut installed on the TR hub body from service and replace with airworthy parts and perform the actions in paragraph (g)(1)(ii) of this AD. (4) Within 24 months after the effective date of this AD, inspect the torque on the nut of the TR hub body in accordance with paragraph 4.1.2 of Airbus Helicopters Alert Service Bulletin ASB EC120-64-21-0001, Issue 001, dated September 19, 2024. (i) If the torque is not within allowable limits, before further flight, remove the nut on the TR hub body from service and replace it with an airworthy nut; and accomplish the actions in paragraph (g)(4)(ii) of this AD. (ii) If the torque is within allowable limits, before further flight, using polyurethane paint, apply a red paint line to the bolt and washer on the TR hub body; and apply a red paint line to the nut and washer on the splined flange. These actions terminate the repetitive inspections and replacements required by paragraphs (g)(1) through (3) of this AD. (5) Within 100 hours TIS or 12 months, whichever occurs first after the action required in paragraph (g)(4)(ii) of this AD, and thereafter at intervals not to exceed 100 hours TIS or 12 months, whichever occurs first, inspect the red paint line for alignment. If the red paint line is misaligned, before further flight, perform the actions as specified in paragraphs (g)(4)(i) of this AD. (h) Parts Installation Limitations As of the effective date of this AD, do not install on any helicopter a TR hub body P/N C642A0100103 or a splined flange unless the part is new (zero hours TIS) or has passed the inspection requirements required by paragraph (g)(1) of this AD. (i) Credit for Previous Actions This paragraph provides credit for the initial instance of the actions required by paragraphs (g)(1) through (3) of this AD, if those actions were performed before the effective date of this AD in accordance with Airbus Helicopters Emergency Alert Service Bulletin 05A020 Revision 0, dated October 29, 2019; Revision 1, dated November 8, 2019; or Revision 2, dated February 8, 2021. (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 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 (k)(1) 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 responsible Flight Standards Office. The following provisions also apply to this AD. (k) Additional Information (1) For more information about this AD, contact Camille Seay, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (817) 222-5149; email: camille.l.seay@faa.gov . (2) For Airbus Helicopters material identified in this AD that is not incorporated by reference, can be found at the contact information identified in paragraph (l)(3) of this AD. (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) Airbus Helicopters Emergency Alert Service Bulletin 05A020, Revision 3, dated September 19, 2024. (ii) Airbus Helicopters Alert Service Bulletin EC120-64-21-0001, Issue 001, dated September 19, 2024. (3) 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; website: airbus.com/en/products-services/helicopters/hcare-services/airbusworld. (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 November 20, 2025. Steven W. Thompson, Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service. [FR Doc. 2025-20946 Filed 11-24-25; 8:45 am]BILLING CODE 4910-13-P