Summary
This notice revises an earlier proposed airworthiness directive (AD), applicable to Turbomeca S.A. Arriel-1 D, 1 D1, 1S, 1 S1, 2 S1, and -2B series turboshaft engines. That proposal would have required the insertion of a sleeve in the attachment boss of the compressor bleed valve. That proposal was prompted by several cases of contained centrifugal compressor impeller blade ruptures that occurred in service. This proposed action revises the proposed rule by retaining the insertion of a sleeve in the attachment boss of the compressor bleed valve, adding requirements for bonding the sleeve in the bleed-valve mounting pad, and expanding the applicability to Turbomeca 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. The actions specified by this proposed 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.