Airworthiness Directives; Pratt & Whitney Canada Corp. Turboshaft Engines

The FAA is superseding Airworthiness Directive (AD) 2015-20-04 for certain Pratt & Whitney Canada Corp. (P&WC) PT6B-37A turboshaft engines. AD 2015-20-04 required initial and repetitive inspections until replacement of the No. 10 bearing, and eventual replacement of the No. 9 bearing, both located in the engine reduction gearbox (RGB) assembly. This AD requires removal from service and replacement of the No. 9 and No. 10 position bearings. This AD was prompted by reports of incorrect engine torque for PT6B-37A turboshaft engines. The FAA is issuing this AD to address the unsafe condition on these products.