Airworthiness Directives; Bell Helicopter Textron Model 212, 412, and 412EP Helicopters

This amendment adopts a new airworthiness directive (AD) for the specified Bell Helicopter Textron (Bell) model helicopters modified with Aeronautical Accessories, Inc. (AAI), Supplemental Type Certificate (STC) SH2820SO or that have the affected AAI Parts Manufacturer Approval (PMA) parts installed. This action requires inspecting a certain part-numbered reservoir assembly adapter (adapter) for the counter bore depth (dimension D). If the dimension D of the adapter exceeds .860 inch, before further flight, this AD requires replacing the reservoir assembly and adapter with airworthy parts. This amendment is prompted by a report of a rupture of an adapter during nitrogen charging because of inadequate wall thickness for the operating pressures. The actions specified in this AD are intended to prevent the rupture of an adapter, uncontrolled jetting of pressurized gas from the nitrogen bottle, and subsequent injury to occupants or damage to the helicopter.