Airworthiness Directives; Turbomeca S.A. Arriel 1 A2, 1 C, 1 C1, 1 C2, 1 D, 1 D1, 1 E2, 1 K, 1 K1, 1 S, 1 S1 and Arriel 2 B, 2 B1, 2 C, 2 C1, 2 S1 Series Turboshaft Engines

This amendment adopts a new airworthiness directive (AD), that is applicable to Turbomeca S.A. Arriel 1 A2, 1 C, 1 C1, 1 C2, 1 D, 1 D1, 1 E2, 1 K, 1 K1, 1 S, 1 S1 and Arriel 2 B, 2 B1, 2 C, 2 C1, 2 S1 series turboshaft engines. This amendment requires the insertion of a sleeve in the attachment boss of the compressor bleed valve, and bonding the sleeve in the bleed-valve mounting pad. This amendment is prompted by several cases of contained centrifugal compressor impeller blade ruptures that occurred in service. The actions specified by this AD are intended to prevent acoustic excitation of the centrifugal compressor impeller blades resulting in contained compressor impeller blade ruptures and power loss that could lead to an uncommanded in- flight shutdown.