Airworthiness Directives; Pratt & Whitney Canada PT6A-25C and -114A Series Turboprop Engines

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This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Pratt & Whitney Canada (P&WC) PT6A-25C and -114A turboprop engines. This proposal would require initial and repetitive visual inspections, and eventual replacement of the compressor bleed valve assembly, with a redesigned valve assembly for the -114A engines, and initial and repetitive visual inspections only for -25C engines. This proposal is prompted by reports of two occurrences of uncommanded engine power loss. The actions specified by the proposed AD are intended to detect wear in the compressor bleed valve assembly which may cause valve orifice blockage, resulting in a loss of power, inability of engine acceleration, and in-flight shut down.