The FAA has adopted a new Airworthiness Directive for the Pratt & Whitney Canada PT6A-15AG, -27, -28, -34, -34AG, -34B and -36 turboprop engines. It requires the removal of certain affected PMA replacement Timken Alcor Aerospace Technologies first-stage reduction sun gears and/or the interacting planetary gear sets from the propeller reduction gearbox assembly. The AD is intended to prevent failure of the sun gear, which will result in an in-flight engine shutdown, possible uncontained engine failure, aircraft damage and serious injuries.