Airworthiness Directives; Turbomeca S.A. Arrius 2 B1, 2 B1A, 2 B1A 1, and 2 K1 Turboshaft Engines

The FAA is adopting a new airworthiness directive (AD) for Turbomeca S.A. Arrius 2 B1, 2 B1A, 2 B1A 1, and 2 K1 turboshaft engines. This AD requires replacement of the gas generator high pressure (HP) turbine disk before further flight after the engine has accumulated 5 minutes of operating time at the 2\1/2\ minute one engine inoperative (OEI) power rating. This amendment is prompted by a failure of an HP turbine blade during accelerated aging simulation tests performed by the manufacturer on an Arrius 2 B1A engine. We are issuing this AD to prevent engine failure of the only operating engine while experiencing an OEI condition.