Airworthiness Directives; Pratt & Whitney Canada PT6B-36A and PT6B-36B Turboshaft Engines

The FAA is adopting a new airworthiness directive (AD) for Pratt & Whitney Canada (PWC) PT6B-36A and PT6B-36B turboshaft engines with compressor rear hubs, part number (P/N) 3018111 installed. This AD requires reviewing, and correcting if necessary the critical part record for compressor rear hubs, P/N 3018111. This AD also requires removing compressor rear hubs from service that exceed the published part life limit, before further flight. This AD results from the discovery of a compressor rear hub, P/N 3018111, that exceeded the published life limit. This occurred because the operator used an incorrect life limit calculation contained in a PWC Service Bulletin. We are issuing this AD to prevent uncontained failure of the compressor rear hub and damage to the airplane.