AD 2021-22-11 Airworthiness Directives; MD Helicopters Inc. (MDHI) Helicopters

Models named: 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, 600N. Read the applicability below — it usually turns on serial or part numbers too.

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.

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

(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.

This AD was prompted by a report of a spiral crack in the torque tube. The FAA is issuing this AD to prevent failure of a torque tube. The unsafe condition, if not addressed, could result in loss of tail rotor control and subsequent loss of control of the helicopter.

None.