AD 99-17-01 64 FR 44112

This amendment adopts a new airworthiness directive (AD) that applies to certain Pilatus Aircraft Ltd. (Pilatus) Models PC-12 and PC- 12/45 airplanes. This AD requires replacing all flap drive shafts with flap drive shafts of improved design, installing additional gaskets on the power drive unit, and modifying the attachment and supporting hardware. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. The actions specified by this AD are intended to prevent the flap drive shafts from corroding to the point where the flexible shafts in the flap drive system rupture, which could result in the inability to utilize the flap system with reduced airplane control.