Airworthiness Directive · Amendment 39-21784 · Tail rotor control system
MD Helicopters Inc. (MDHI) Helicopters
This AD applies to MD Helicopters Inc. (MDHI) Model 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters, certificated in any category, with pilot-to-copilot tail rotor torque tube (torque tube) part number 369H7531-9/-11/-13, installed.
The FAA is adopting a new airworthiness directive (AD) for certain MD Helicopters Inc. (MDHI), Model 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters. This AD was prompted by a report of a spiral crack in the pilot-to-copilot tail rotor torque tube (torque tube). This AD requires a one-time visual and recurring borescope inspections of the torque tube and depending on the results, removing the torque tube from service. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Using a flashlight and mirror, visually inspect the exterior of the torque tube at the interface of the torque tube and bushing segments, and borescope inspect the interior of the torque tube at the interface of the torque tube and bushing segments for a crack, elongation, and other damage, which may be indicated by any corrosion, pitting, crazing, dents, dings, displacement of material at the bolt hole edge, or fretting of the hole by following the Accomplishment Instructions, paragraphs 2.A.(1). through (3).(a)., of MD Helicopters Service Bulletin SB369H-263R2, SB369D-229R2, SB369E-129R2, SB369F-119R2, SB500N-066R2, or SB600N-080R2, each dated March 24, 2021, as applicable to your model helicopter, as follows:
Note 1 to the introductory text of paragraph (g)(1): Scaling of the inner diameter primer or paint may be an indication of a crack.
(i) For helicopters that have accumulated 600 or less total hours time-in-service (TIS), within 100 hours TIS after the effective date of this AD.
(ii) For helicopters that have accumulated more than 600 total hours TIS, within 5 hours TIS or 30 days after the effective date of this AD, whichever occurs later. Note 2 to paragraph (g)(1)(ii): It is advised to limit flights with increased, excessive, or rapid pedal movements before the first instance of the actions required by paragraph (g)(1)(ii) of this AD are accomplished.
(iii) If there is a crack, elongation, or other damage, before further flight, remove the torque tube from service.
(2) Thereafter following paragraph (g)(1) of this AD, at intervals not to exceed 300 hours TIS, borescope inspect the interior of the torque tube at the interface of the torque tube and bushing segments as required by paragraph (g)(1) of this AD. If there is a crack, elongation, or other damage, before further flight, remove the torque tube from service.
