Airworthiness Directives; Pilatus Aircraft Ltd. Models PC-12 and PC-12/45 Airplanes

We are adopting a new airworthiness directive (AD) for all Pilatus Aircraft Ltd. Models PC-12 and PC-12/45 airplanes equipped with certain crew seat bucket assemblies with and without a backrest recline system. This AD requires you to replace the backrest tubes on these crew seat bucket assemblies at a specified time and adds a life limit for these backrest tubes. This AD results from mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. We are issuing this AD to prevent cracks in the backrest tubes of certain crew seat bucket assemblies, which could result in failure of the seat system. This failure could lead to the pilot and co-pilot's reduced ability to control the airplane. This failure could also affect the proper function of the seat restrain system in the case of an emergency landing.