# [Amended]
**AGENCY:**
Federal Aviation Administration (FAA), DOT.
**ACTION:**
Notice of proposed rulemaking (NPRM).
**SUMMARY:**
The FAA proposes to supersede Airworthiness Directive (AD) 2024-23-06, which applies to certain MD Helicopters, LLC (MDHI) Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters. AD 2024-23-06 requires repetitively inspecting the torque tube assembly and roller bearings, and depending on the results, replacing parts or accomplishing additional inspections. Since the FAA issued AD 2024-23-06, it has been determined that additional torque tube assemblies are affected by this unsafe condition. This proposed AD would continue to require the actions of AD 2024-23-06 and would expand the applicability. 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 January 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-2025-3987; 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.
**FOR FURTHER INFORMATION CONTACT:**
Eduardo Orozco-Duran, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: (562) 627-5264; 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 using a method listed under the *ADDRESSES* section. Include “Docket No. FAA-2025-3987; Project Identifier AD-2025-00017-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 Eduardo Orozco-Duran, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712. 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 2024-23-06, Amendment 39-22885 (89 FR 91248, November 19, 2024) (AD 2024-23-06), for MDHI Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters with a pilot interconnecting cyclic torque tube (torque tube) part number 369H7133-7 installed. AD 2024-23-06 was prompted by a report of a seized and damaged roller bearing assembly in the torque tube assembly of an MDHI Model MD369E helicopter. This damage did not allow the torque tube to rotate as designed, which initiated a crack and resulted in an emergency landing. The seized roller bearings were due to rust compounded with dried grease residue and an aggressive chemical environment. Because the seized roller bearings did not allow the torque tube to rotate freely, additional torsional stresses occurred on the torque tube, which caused a crack to initiate and eventually propagate until the part failed and longitudinal control was lost. Since certain MDHI Model 369, 369A, 369D, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters have the same torque tube assembly installed, they are also affected by this unsafe condition. AD 2024-23-06 requires repetitive visual inspections of the torque tube for corrosion and cracks, repetitive visual inspections of the roller bearings for corrosion and degradation, a repetitive freedom-of-movement inspection of the torque tube assembly for binding or ratcheting, and corrective or additional action as necessary. The FAA issued AD 2024-23-06 to prevent failure of the torque tube assembly which, if not addressed, could result in reduced controllability and subsequent loss of control of the helicopter.
**Actions Since AD 2024-23-06 Was Issued**
Since AD 2024-23-06 was issued, the FAA received a report that additional torque tube assemblies are affected by this unsafe condition and should be included in the AD action. Due to this determination, this proposed AD would expand the applicability to include all MD Helicopters, LLC Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters regardless of the torque tube part number.
**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.
**Proposed AD Requirements in This NPRM**
This proposed AD would retain all requirements of AD 2024-23-06 and expand the applicability by removing the specific part number requirement.
**Costs of Compliance**
The FAA estimates that this AD, if adopted as proposed, would affect 353 helicopters of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:
| Action | Labor cost | Parts cost | Cost per | Cost on U.S. |
| --- | --- | --- | --- | --- |
| Visual inspection of torque tube and roller bearings | 1 work-hour × $85 per hour = $85 | $0 | $85 | $30,005 |
| Inspection of torque tube for freedom-of-movement | 0.75 work-hours × $85 per hour = $64 | 0 | 64 | 22,592 |
The FAA estimates the following costs to do any necessary replacements 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 replacements:
| Action | Labor cost | Parts cost | Cost per |
| --- | --- | --- | --- |
| Replacement of torque tube | 6 work-hours × 85 per hour = $510 | $4,773 | $5,283 |
| Visual inspection of roller bearings | 0.25 work-hour × $85 per hour = $21 | 0 | 21 |
| Replacement of roller bearing | 6 work-hours × 85 per hour = $510 | 210 | 720 |
**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 AD 2024-23-06, Amendment 39-22885 (89 FR 91248, November 19, 2024); and
b. Adding the following new airworthiness directive:
*MD Helicopters, LLC:* Docket No. FAA-2025-3987; Project Identifier AD-2025-00017-R.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by January 2, 2026.
**(b) Affected ADs**
This AD replaces AD 2024-23-06, Amendment 39-22885 (89 FR 91248, November 19, 2024) (AD 2024-23-06).
**(c) Applicability**
This AD applies to MD Helicopters, LLC Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters, certificated in any category.
**(d) Subject**
Joint Aircraft System Component (JASC) Code 6700, Rotorcraft Flight Control.
**(e) Unsafe Condition**
This AD was prompted by a report of a seized and damaged roller bearing in the torque tube assembly. The FAA is issuing this AD to prevent failure of the torque tube assembly. The unsafe condition, if not addressed, could result in reduced controllability and subsequent loss of control of the helicopter.
**(f) Compliance**
Comply with this AD within the compliance times specified, unless already done.
**(g) Required Actions**
(1) Within 100 hours time-in-service (TIS) or within 12 months after the effective date of this AD, whichever occurs first, and thereafter at intervals not to exceed 100 hours TIS, accomplish the actions required by paragraphs (g)(1)(i) and (ii) of this AD.
(i) Using a flashlight and mirror, visually inspect the torque tube for corrosion and cracks. If there is any corrosion or a crack, before further flight, remove the torque tube from service and install an airworthy torque tube.
(ii) Visually inspect each roller bearing (number 5) as depicted in Figure 1 to paragraph (g)(1) of this AD for corrosion and degradation. If a roller bearing has any corrosion or degradation, before further flight, remove the roller bearing from service and install an airworthy roller bearing.
(2) Before the helicopter accumulates 3,000 total hours TIS or within 100 hours TIS after the effective date of this AD, whichever occurs later, and thereafter at intervals not to exceed 100 hours TIS, perform a freedom-of-movement inspection on the torque tube assembly by accomplishing the actions required by paragraphs (g)(2)(i) through (v) of this AD.
(i) Disconnect the one-way lock (number 6) of the torque tube by removing the cotter pin (number 7), nut (number 8), bolt (number 9), washers (number 10), and slotted bushing (number 11) from the torque tube assembly as depicted in Figure 1 to paragraph (g)(1) of this AD.
(ii) Loosen the longitudinal cyclic friction knob (number 12 or 13) of the torque tube assembly as depicted in Figure 1 to paragraph (g)(1) of this AD.
(iii) While moving the cyclic control forward and aft to allow the torque tube assembly to rotate through its full range of motion, inspect the torque tube assembly for binding and ratcheting.
(A) If there is any binding or ratcheting as a result of the action required by paragraph (g)(2)(iii) of this AD, before further flight, inspect each roller bearing (number 5) as depicted in Figure 1 to paragraph (g)(1) of this AD for damage. For the purposes of this inspection, damage may be indicated by corrosion, lack of lubrication (dry exterior surface), or material degradation.
(B) If any roller bearing (number 5) as depicted in Figure 1 to paragraph (g)(1) of this AD has any damage, before further flight, remove the roller bearing from service and install an airworthy roller bearing.
(iv) If there is not any binding or ratcheting as a result of the action required by paragraph (g)(2)(iii) of this AD or after accomplishing the action required by paragraph (g)(2)(iii)(B) of this AD, as applicable, tighten the cyclic friction knob (number 12 or 13) as depicted in Figure 1 to paragraph (g)(1) of this AD.
(v) Connect the one-way lock (number 6) as depicted in Figure 1 to paragraph (g)(1) of this AD by accomplishing the actions required by paragraphs (g)(2)(v)(A) and (B).
(A) Install the slotted bushing (number 11), washers (number 10), bolt (number 9), nut (number 8), and new (zero total hours TIS) cotter pin (number 7) as depicted in Figure 1 to paragraph (g)(1) of this AD.
(B) Ensure the edge of the slotted bushing (number 11) protrudes 0.010 to 0.080 inch (0.25 to 2.03 mm) above the surface of the cyclic torque tube after the nut is tightened.
**(h) Alternative Methods of Compliance (AMOCs)**
(1) The Manager, West 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 responsible Flight Standards Office, as appropriate. If sending information directly to the manager of the West Certification Branch, send it to the attention of the person identified in paragraph (i) 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 local flight standards district office/certificate holding district office.
**(i) Additional Information**
For more information about this AD, contact Eduardo Orozco-Duran, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: (562) 627-5264; email: *[email protected].*
**(j) Material Incorporated by Reference**
None.
Issued on October 22, 2025.
Christopher R. Parker,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.