Airworthiness Directives; Turbomeca S.A. Turboshaft Engines

We are adopting a new airworthiness directive (AD) for all Turbomeca S.A. Arrius 2B1, 2B1A, 2B2, and 2K1 turboshaft engines. This AD requires initial and repetitive inspections of the hydro-mechanical metering unit (HMU) high pressure pump drive gear shaft splines, cleaning and inspections of the sleeve assembly splines, and replacement of the HMU if it fails inspection. This AD was prompted by in-flight shutdowns caused by interrupted fuel supply at the HMU. We are issuing this AD to prevent in-flight shutdown and damage to the engine.