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-2026-11819; Project Identifier AD-2025-01199-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 Binod Singh, 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 90-19-02, Amendment 39-6716 55 FR 36270 (September 5, 1990) (AD 90-19-02), for certain McDonnell Douglas Helicopter Company (MDHC) Model 369 series helicopters. AD 90-19-02 was prompted by reports of sprag element chipping and wear of the sprag, cage, and the inner and outer races of the overrunning clutch assembly on all MDHC model helicopters equipped with a cargo hook. AD 90-19-02 requires removing and replacing certain overrunning clutch assemblies. AD 90-19-02 also requires repetitively inspecting certain overrunning clutch assemblies with a certain subassembly installed, and replacing certain sprag assemblies before exceeding a specified life limit. The FAA issued AD 90-19-02 to prevent an overrunning clutch assembly failure, which may result in the loss of engine power to the main rotor.

Actions Since AD 90-19-02 Was Issued

Since the FAA issued AD 90-19-02, an incident occurred involving an MD Helicopters Model 369E helicopter that resulted in a forced emergency landing ( printed page 69226) due to a total loss of engine power. Subsequent investigation revealed that the in-flight loss of engine power was the direct result of inadequate regreasing of the overrunning clutch output bearing, which caused frictional heating and thermal damage to the clutch inner race, ultimately leading to clutch inner race failure. The investigation also determined that a gap in the applicability of AD 90-19-02 was inadvertently introduced subsequent to the original publication of the AD, allowing certain aircraft to operate without the mandated inspections or modifications. The FAA has determined that MD Helicopters Model 500N helicopters are also affected by the same unsafe condition. The FAA is proposing this AD to ensure the unsafe condition is addressed on these additional helicopters. Additionally, since the FAA issued AD 90-19-02, inspection intervals of the sprag assembly, clutch inner and outer races have been introduced in the ALS of the helicopters' maintenance manual.

FAA's Determination

The FAA is proposing 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 require for helicopters with certain overrunning clutch assemblies installed, removing from service a certain overrunning clutch subassembly, if installed, and installing certain clutch subassemblies or replacing the clutch assembly with a different part-numbered clutch assembly. This proposed AD would also require reidentifying the overrunning clutch assembly, as applicable.

This proposed AD would require for certain model helicopters, revising the ALS of the existing AMM or ICA and the existing approved maintenance or inspection program, as applicable, by incorporating the actions and associated thresholds and intervals specified in this proposed AD.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 568 helicopters of U.S. registry.

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

Note:

The FAA believes that most helicopters have incorporated overrunning clutch assembly part number (P/N) 369A5350-605 and thus have also incorporated overrunning clutch subassembly P/N 369A5350-41 or 369A5350-51.

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.

The Proposed Amendment

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

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 90-19-02, Amendment 39-6716 ( 55 FR 36270, September 5, 1990); and

b. Adding the following new airworthiness directive:

MD Helicopters, LLC: Docket No. FAA-2026-11819; Project Identifier AD-2025-01199-R.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by December 18, 2026.

(b) Affected ADs

This AD replaces AD 90-19-02, Amendment 39-6716 (55 FR 36270, September 5, 1990) (AD 90-19-02).

(c) Applicability

This AD applies to all MD Helicopters, LLC Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, and 500N helicopters, certified in any category, equipped with a cargo hook. ( printed page 69227)

(d) Subject

Joint Aircraft System Component (JASC) Code 6320, Main rotor drive gearbox/clutch assembly.

(e) Unsafe Condition

This AD was prompted by reports of sprag element chipping and wear of the sprag, cage, and inner and outer races of the overrunning clutch assemblies. The FAA is issuing this AD to prevent overrunning clutch assembly failures caused by such chipping and wear. The unsafe condition, if not addressed, could result in loss of power to the main rotor and 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 with an overrunning clutch assembly part number (P/N) 369A5350-BSC, 369A5350-601, or 369A5350-603 installed, within 300 hours time-in-service (TIS) or at the next annual inspection, whichever occurs first after the effective date of this AD, accomplish all of the following:

(i) Remove from service any overrunning clutch subassembly that does not have P/N 369A5350-41 or 369A5350-51.

(ii) If the overrunning clutch subassembly was removed in accordance with paragraph (g)(1)(i) of this AD, install overrunning clutch subassembly P/N 369A5350-41 or 369A5350-51.

(iii) Reidentify overrunning clutch assembly to P/N 369A5350-605.

(2) For all helicopters except for Model 369 and 369A helicopters, within 30 days after the effective date of this AD: Revise the airworthiness limitations section (ALS) of the existing aircraft maintenance manual (AMM) or instructions for continued airworthiness (ICA), and the existing approved maintenance or inspection program, as applicable, by incorporating the information identified in table 1 to paragraph (g)(2) of this AD.

(3) For Model 369 and 369A helicopters, within 30 days after the effective date of this AD, revise the ALS of the existing AMM or ICA, and the existing approved maintenance or inspection program, as applicable, in accordance with a method approved by the Manager, West Certification Branch, FAA.

Note 1 to Table 1 of this AD:

For the sprag assembly with cargo hook attached and no separate log, the finite life hours is 1,800 hours; with cargo hook attached and with separate log: 1,800 hours of external load operating time when logged separately.

(h) Provisions for Alternative Actions and Intervals

After the action required by paragraph (g)(2) or (g)(3) of this AD has been done, no alternative actions and associated thresholds and intervals are allowed unless they are approved as specified in the provisions of paragraph (i) of this AD.

(i) 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 (j) 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.

(j) Additional Information

For more information about this AD, contact Binod Singh, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: (562) 627-5264; email: binod.singh@faa.gov.

(k) Material Incorporated by Reference

None.

91 FR 69225