Airworthiness Directive · Amendment 39-17925 · Main rotor head
MD Helicopters, Inc., Helicopters
Superseded. A later AD replaced this one: AD 2017-17-03. Comply with the one in force.
This AD applies to Model MD900 helicopters, serial numbers 900-00008 through 900-00140, with main rotor upper hub assembly (upper hub) part number 900R2101006-105, -107, -109, or -111 installed, certificated in any category.
We are adopting a new airworthiness directive (AD) for MD Helicopters, Inc. (MDHI), Model MD900 helicopters. This AD requires an eddy current inspection of the main rotor upper hub assembly (upper hub) for a crack and replacing the upper hub with an airworthy upper hub before further flight if there is a crack. This AD is prompted by a report of cracks on an upper hub at the blade attach holes. The actions specified by this AD are intended to detect a crack in the upper hub to prevent failure of the upper 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 previously accomplished.
Within the next 25 hours time-in-service (TIS) or at the next annual inspection, whichever occurs first:
(1) Clean each upper hub inspection area as shown in Figure 1 of MD Helicopters Service Bulletin SB900-122, dated April 8, 2014 (SB900-122).
(2) Eddy current inspect the upper hub for a crack by following the Accomplishment Instructions, paragraphs 2.A.(3) through 2.A.(11) of SB900-122. This eddy current inspection must be performed by a Level II or higher technician with the National Aerospace Standard 410 or equivalent certification who has performed an eddy current inspection within the last 12 months. If there is a crack, before further flight, replace the upper hub with an airworthy upper hub.
