FAA Proposes Airworthiness Directive for Sikorsky Helicopter Tail Rotor Blades

Proposed Rule

Airworthiness Directives; Various Helicopters

A Proposed Rule by the Federal Aviation Administration on 04/23/2026

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• Public Inspection Published Document: 2026-07937 (91 FR 21738) Document Headings ###### Department of Transportation

Federal Aviation Administration

1. 14 CFR Part 39
2. [Docket No. FAA-2026-3863; Project Identifier AD-2024-00567-R]
3. RIN 2120-AA64

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede Airworthiness Directive (AD) 2020-02-17, which applies to certain Sikorsky Aircraft Corporation (Sikorsky) Model S-70, S-70A, S-70C, S-70C(M), and S-70C(M1) helicopters. AD 2020-02-17 requires recurring visual and tap inspections of the tail rotor blade (TRB) and, depending on the results, replacing the TRB. Since the FAA issued AD 2020-02-17, it was determined additional helicopter models are affected by the unsafe condition. The manufacturer has developed a split pitch horn modification and a safety enhancement modification kit for the TRB. This proposed AD would continue to require the actions of AD 2020-02-17, would expand the applicability, and would require modifying and re-identifying the TRB. This proposed AD would also require revising the airworthiness limitations section (ALS) of the existing helicopter maintenance manual or instructions for continued airworthiness and the existing approved maintenance or inspection program, as applicable, to incorporate recurring inspections of the TRB disbond indicator. The FAA is proposing this AD to address the unsafe condition on these products.

DATES:

The FAA must receive comments on this proposed AD by June 8, 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-2026-3863; 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, any comments received, and other information. The street address for Docket Operations is listed above.

Material Incorporated by Reference:

• For Sikorsky material identified in this proposed AD, contact your local Sikorsky Field Representative or Sikorsky's Service Engineering Group at Sikorsky Aircraft Corporation, 124 ( printed page 21739) Quarry Road, Trumbull, CT 06611; phone: (800) Winged-S or (203) 416-4299; email: wcscustservice_eng.gr-sik@lmco.com. Operators may also log on to the Sikorsky 360 website at sikorsky360.com.
• 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. It is also available at regulations.gov under Docket No. FAA-2026-3863.

FOR FURTHER INFORMATION CONTACT:

Isabel Saltzman, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone: (781) 238-7649; email: ECB-COS@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments using a method listed under ADDRESSES. Include “Docket No. FAA-2026-3863; Project Identifier AD-2024-00567-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 revise this 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 Isabel Saltzman, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337. 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 2020-02-17, Amendment 39-21025 (85 FR 7191, February 7, 2020) (AD 2020-02-17), for Sikorsky Model S-70, S-70A, S-70C, S-70C(M), and S-70C(M1) helicopters with a TRB part number 70101-31000 (all dash numbers) with a serial number up to and including A009-08915. AD 2020-02-17 was prompted by four incidents of disbonding between the TRB pitch horn and the torque tube. AD 2020-02-17 requires recurring visual and tap inspections of the TRB and, depending on the results, replacing the TRB. The agency issued AD 2020-02-17 to detect disbonding. The unsafe condition, if not addressed, could result in increased tail rotor vibrations, physical failure of the torque tube, and consequent loss of control of the helicopter.

Actions Since AD 2020-02-17 Was Issued

Since the FAA issued AD 2020-02-17, a determination was made that Sikorsky Model S-70M helicopters and restricted category military surplus Models EH-60A, HH-60L, UH-60A, and UH-60L helicopters are also affected by the unsafe condition defined in AD 2020-02-17. Sikorsky has developed a split pitch horn modification for certain TRBs and a safety enhancement modification kit for certain TRBs, which consists of a disbond indicator (three white stripes applied to both upper and lower airfoil blade surfaces). Sikorsky has also issued a temporary revision to the maintenance manual to specify procedures for recurring inspections of the disbond indicator for TRBs modified with the safety enhancement modification kit. In addition, Sikorsky updated the service information into two separate bulletins based on the TRB manufactured date. A manufacturing improvement was implemented between 2006 and 2007, and the service bulletin reflects this difference.

FAA's Determination

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.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Sikorsky Aircraft Model S-70A Blackhawk Derivatives Maintenance Manual Temporary Revision No. 82, dated June 27, 2023. This material specifies procedures for the visual, tap test, and borescope inspections of the modified TRBs with the disbond indicator. This material also provides instructions for maintaining the disbond indicator.

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.

Proposed AD Requirements in This NPRM

This proposed AD would continue to require the actions of AD 2020-02-17. This proposed AD would require modifying and re-identifying the TRB. This proposed AD would also require revising the ALS of the existing helicopter maintenance manual or instructions for continued airworthiness and the existing approved maintenance or inspection program, as applicable, to incorporate recurring inspections of the TRB disbond indicator. This proposed AD would also expand the applicability by adding helicopter models.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 96 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.
operators |
| --- | --- | --- | --- | --- |
| Inspect and tap test TRBs (retained from AD 2020-02-17) | 1 work-hour × $85 per hour = $85 | $0 | $85 per inspection cycle | $8,160 per inspection cycle. |
| Install split pitch horn modification (for certain TRBs) | 6 work-hours × $85 per hour = $510 | 50,000 | 50,510 | Up to $4,848,960. |
| Install safety enhancement modification kit (for certain TRBs) | 6 work-hours × $85 per hour = $510 | 300,000 | 300,510 | Up to $28,848,960. |
| Revise ALS | 1 work-hour × $85 per hour = $85 | 0 | 85 | $8,160. |
The FAA estimates the following costs to do any on-condition actions that would be required based on the results of the proposed inspection. The agency has no way of determining the number of helicopters that might need these on-condition actions:

| Action | Labor cost | Parts cost | Cost per
product |
| --- | --- | --- | --- |
| Perform tap test or borescope inspection | 1 work-hour × $85 per hour = $85 | $0 | $85 |
| Replace TRBs
(set of two—unmodified) | 6 work-hours × $85 per hour = $510 | 192,304 | 192,814 |

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 [Amended] 2. The FAA amends § 39.13 by:

a. Removing Airworthiness Directive 2020-02-17, Amendment 39-21025 (85 FR 7191, February 7, 2020); and

b. Adding the following new airworthiness directive:

Various Helicopters: Docket No. FAA-2026-3863; Project Identifier AD-2024-00567-R.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by June 8, 2026.

(b) Affected ADs

This AD replaces AD 2020-02-17, Amendment 39-21025 (85 FR 7191, February 7, 2020) (AD 2020-02-17).

(c) Applicability

This AD applies to the helicopters listed in paragraphs (c)(1) through (5) of this AD, certificated in any category, with a tail rotor blade (TRB) part number (P/N) 70101-31000 (all dash numbers) installed.

(1) Model EH-60A helicopters; type certificate holders include, but are not limited to, Delta Enterprise, LLC; Heliqwest International Inc.; Pickering Aviation, Inc.; and Sixtyhawk TC, LLC.

(2) Model HH-60L helicopters; type certificate holders include, but are not limited to, Capitol Helicopters Inc.; Central Copters Inc.; and Sixtyhawk TC, LLC.

(3) Sikorsky Aircraft Corporation Model S-70, S-70A, S-70C, S-70C(M), S-70C(M1), and S-70M helicopters.

(4) Model UH-60A helicopters; type certificate holders include, but are not limited to, ACE Aeronautics, LLC.; Air Resources Helicopters Inc.; Billings Flying Service Inc.; Blackhawk Mission Equipment; Capitol Helicopters Inc.; Carson Helicopters, Inc.; Delta Enterprise, LLC; H-60, LLC; Hallux Aerospace, LLC.; Heliqwest International Inc.; High Performance Helicopters Corp.; Northwest Rotorcraft LLC; Pickering Aviation, Inc.; PJ Helicopters Inc.; Reeder Flying Service Inc.; Sixtyhawk TC, LLC; Skydance Blackhawk Operations, LLC; Timberline Helicopters, Inc.; and Unical Air Inc.

(5) Model UH-60L helicopters; type certificate holders include, but are not limited to, ACE Aeronautics, LLC.; Air Resources Helicopters Inc.; Delta Enterprise, LLC; H-60, LLC.; Hallux Aerospace, LLC.; Pickering Aviation, Inc.; and Timberline Helicopters, Inc.

(d) Subject

Joint Aircraft System Component (JASC) Code 6400, Tail Rotor System.

(e) Unsafe Condition

This AD was prompted by four incidents of disbonding between the TRB pitch horn ( printed page 21741) and the torque tube. The FAA is issuing this AD to detect and address disbonding. The unsafe condition, if not addressed, could result in increased tail rotor vibrations, physical failure of the torque tube, and consequent loss of control of the helicopter.

(f) Compliance

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

(g) TRB Inspection With Applicable Corrective Actions

For helicopters with TRB P/N 70101-31000 (all dash numbers), before the first flight of each day:

(1) Visually inspect each TRB for a crack, leading edge erosion, and trailing edge skin disbonding and separation, paying particular attention to the area from the midspan to the pitch control horn. If there is a crack, any leading edge erosion, trailing edge disbonding, or trailing edge separation, before further flight, remove the TRB from service and replace with a serviceable part.

(2) Tap test inspect each TRB for disbonding in the pitch horn to torque tube bond area. If there is any disbonding, before further flight remove the TRB from service and replace with a serviceable part.

(h) TRB Modification and Applicable Re-Identification

(1) For helicopters with TRB P/N 70101-31000-043, P/N 70101-31000-048, P/N 70101-31000-050, P/N 70101-31000-051, or P/N 70101-31000-052 without a split pitch horn installed, accomplish the safety enhancement modification kit. This action must be accomplished by an authorized Sikorsky Aircraft overhaul facility, or by a method approved by the Manager, East Certification Branch, FAA, within the compliance time specified in paragraph (h)(1)(i) or (ii) of this AD.

Note 1 to the introductory text of paragraph (h)(1): Upon completion of the safety enhancement modification kit, the TRB is marked with P/N 70070-10052-041.

Note 2 to the introductory text of paragraph (h)(1): Information on the safety enhancement modification kit is in Sikorsky Aircraft Corporation (Sikorsky) Alert Service Bulletin 70-05-52, Revision B, dated March 27, 2025, and Sikorsky Alert Service Bulletin 70-05-58, Revision A, dated July 10, 2025.

(i) TRBs manufactured on or before December 31, 2007: within 12 months after the effective date of this AD.

(ii) TRBs manufactured on or after January 1, 2008: within 48 months after the effective date of this AD.

(2) For helicopters with TRB P/N 70101-31000-046 without a split pitch horn installed, accomplish the split pitch horn modification. This action must be accomplished by an authorized Sikorsky Aircraft overhaul facility or by a method approved by the Manager, East Certification Branch, FAA, within the compliance time specified in paragraph (h)(2)(i) or (ii) of this AD.

Note 3 to the introductory text of paragraph (h)(2): Upon completion of the split pitch horn modification, the TRB is marked with P/N 70070-15005-042.

Note 4 to the introductory text of paragraph (h)(2): Information on the split pitch horn modification is in Sikorsky Alert Service Bulletin 70-05-52, Revision B, dated March 27, 2025, and Sikorsky Alert Service Bulletin 70-05-58, Revision A, dated July 10, 2025.

(i) TRBs manufactured on or before December 31, 2007: within 12 months after the effective date of this AD.

(ii) TRBs manufactured on or after January 1, 2008: within 48 months after the effective date of this AD.

(i) Revise Maintenance Procedures Manual

Upon completion of the modification required by paragraph (h)(1) of this AD (when the TRB P/N is changed to P/N 70070-10052-041), revise the airworthiness limitation section of the existing helicopter maintenance manual or instructions for continued airworthiness and the existing approved maintenance or inspection program, as applicable, by incorporating Sikorsky Aircraft Model S-70A Blackhawk Derivatives Maintenance Manual Temporary Revision No. 82, dated June 27, 2023.

(j) Provisions for Alternative Actions and Intervals

After the action required by paragraph (i) of this AD has been done, no alternative actions and associated intervals are allowed unless they are approved as specified in the provisions of the alternative methods of compliance (AMOC) paragraph.

(k) Alternative Methods of Compliance (AMOCs)

(1) The Manager, East Certification 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 East Certification Branch, send it to the attention of the person identified in paragraph (l)(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 local flight standards district office/certificate holding district office.

(l) Additional Information

(1) For more information about this AD, contact Isabel Saltzman, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone: (781) 238-7649; email: ECB-COS@faa.gov.

(2) Material identified in this AD that is not incorporated by reference is available at the address specified in paragraph (m)(3) of this AD.

(m) 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) Sikorsky Aircraft Corporation Model S-70A Blackhawk Derivatives Maintenance Manual Temporary Revision No. 82, dated June 27, 2023.

(ii) [Reserved]

(3) For Sikorsky Aircraft Corporation material identified in this AD, contact your local Sikorsky Field Representative or Sikorsky's Service Engineering Group at Sikorsky Aircraft Corporation, 124 Quarry Road, Trumbull, CT 06611; phone 1-800-Winged-S or 203-416-4299; email wcscustservice_eng.gr-sik@lmco.com. Operators may also log on to the Sikorsky 360 website at sikorsky360.com.

(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.

Issued on April 20, 2026.

Steven W. Thompson,

Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.

[FR Doc. 2026-07937 Filed 4-22-26; 8:45 am]

BILLING CODE 4910-13-P

Published Document: 2026-07937 (91 FR 21738)