Airworthiness Directives; Turbomeca S.A. Turboshaft Engines

We are adopting a new airworthiness directive (AD) for certain Turbomeca S.A. Arriel 2B, 2B1, 2C, 2C1, 2C2, 2D, 2E, 2S1, and 2S2 turboshaft engines. This AD requires inspection, and, depending on the results, removal of the engine accessory gearbox (AGB). This AD was prompted by a report of an uncommanded in-flight shutdown (IFSD) of an Arriel 2 engine caused by rupture of the 41-tooth gear, which forms part of the bevel gear in the engine AGB. We are issuing this AD to prevent failure of the engine AGB, which could lead to in-flight shutdown, damage to the engine, and damage to the aircraft.