FAA Expands Airworthiness Directive for MD Helicopters Torque Tube Assemblies

What the Rule Does

The Federal Aviation Administration is issuing a final rule superseding Airworthiness Directive (AD) 2024-23-06, which applied to certain MD Helicopters, LLC Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters. The new AD continues all actions required by AD 2024-23-06 — namely, repetitively inspecting the torque tube assembly and roller bearings, and depending on the results, replacing parts or accomplishing additional inspections — and expands applicability to cover all MD Helicopters, LLC helicopters of those same model designations regardless of the torque tube part number.

Background and Rationale

AD 2024-23-06 was itself prompted by a report of a seized and damaged roller bearing assembly in the torque tube assembly of an MD Helicopters, LLC Model 369E helicopter. The FAA subsequently received a report indicating that additional torque tube assemblies beyond those covered by AD 2024-23-06 are affected by the same unsafe condition, necessitating the expanded scope of the new directive. The FAA states the purpose of this AD is to prevent failure of the torque tube assembly, which, if not addressed, could result in reduced controllability and loss of control of the helicopter.

Rulemaking Process

The FAA published a Notice of Proposed Rulemaking (NPRM) on November 18, 2025 (90 FR 51596), providing a 45-day comment period. The original AD 2024-23-06 had been issued as Amendment 39-22885 (89 FR 91248, November 19, 2024). The FAA received comments from the Citizens Rulemaking Alliance on three issues: a request to forgo the final rule in favor of a renewed NPRM with a comment period or a 30-to-60-day deferred effective date; a request to supplement the AD docket with risk assessment data, background report data, and a summary of alternatives considered; and a request to address Paperwork Reduction Act (PRA) compliance.

The FAA responded to each comment without making changes to the AD. On the procedural question, the agency noted that the comment was submitted in response to an NPRM for which a 45-day comment period had already been provided, and that the final rule is effective 35 days after publication. On the docket supplement request, the FAA stated that the background, basis, and rationale for the rulemaking were disclosed in the NPRM preamble and available to the public during the comment period, and that the agency evaluated but rejected the alternative of not promulgating the AD, determining that relying on voluntary compliance would leave the unsafe condition unaddressed and would not ensure an acceptable level of safety. On the PRA question, the FAA clarified that this AD does not require reporting.

What to Watch

The rule is effective October 20, 2026, amending 14 CFR part 39. Operators of all MD Helicopters, LLC Model 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters should confirm compliance with the expanded applicability criteria, particularly as the directive now applies regardless of the torque tube part number installed.

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