Airworthiness Directive · Amendment 39-17216 · Equipment/furnishing system wiring
MD Helicopters, Inc.
This AD applies to MDHI Model MD900 helicopters with main rotor lower hub assembly (lower hub) part number 900R2101008-107, with serial numbers beginning with 5009, certificated in any category.
We are adopting a new airworthiness directive (AD) to supersede an existing airworthiness directive for MD Helicopters, Inc. (MDHI), Model MD900 helicopters. The existing AD requires a visual inspection, and if necessary, an eddy current inspection of the main rotor lower hub assembly (lower hub) for a crack. If a crack exists, the AD requires replacing the lower hub with an airworthy lower hub before further flight. Because that AD was immediately effective, we declined to require certain long-term actions prior to public comment. This superseding AD will require the same inspections as the existing AD but will also require long-term recurring inspections and replacing the lower hub with an airworthy lower hub. We are issuing this AD to detect a crack in the lower hub and prevent failure of the lower hub and subsequent loss of control of the helicopter.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
(1) Within 100 hours time-in-service (TIS) or during the next annual inspection, whichever occurs first, unless done within the last 200 hours TIS, and thereafter at intervals not to exceed 300 hours TIS or during the next annual inspection, whichever occurs first:
(i) Visually inspect the sides and bottom of the area between the arms for the centering bearing and the areas adjacent to the bushings of the lower hub assembly for a crack. If there is a crack, before further flight, replace the lower hub with an airworthy lower hub.
(ii) If the lower hub is not replaced as a result of the visual inspection required by paragraph (f)(1)(i) of this AD, eddy current inspect the lower hub for a crack by following the Accomplishment Instructions, paragraphs 2.A(2) through 2.A.(10)., of MD Helicopters Inc. Service Bulletin SB900-117, dated January 14, 2011. If there is a crack, before further flight, replace the lower hub with an airworthy hub.
(2) The eddy current inspection required by paragraph (f)(1)(ii) of this AD must be done by a Level II technician with ASNT-TC-1A, CEN EN 4179, MIL-STD-410, NAS410, or equivalent certification in eddy current inspections. The technician must have done an eddy current inspection in the last 12 months.
(3) Within 3 years, replace the lower hub with an airworthy lower hub not included in the Applicability section of this AD. This replacement is terminating action for the requirements of this AD.
