Summary
We propose to adopt a new airworthiness directive (AD) for all Turbomeca S.A. Arrius 2B1, 2B1A, 2B2, and 2K1 turboshaft engines. This proposed AD was prompted by in-flight shutdowns caused by interrupted fuel supply at the hydro-mechanical metering unit (HMU). This proposed AD would require initial and repetitive inspections of the 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. We are proposing this AD to prevent in-flight shutdown and damage to the engine.