Summary
We propose to revise Airworthiness Directive (AD) 68-17-03, which applies to all Pilatus Aircraft Ltd. PC-6 series airplanes. AD 68-17-03 currently requires you to repetitively inspect the rudder end rib for cracks and replace the rudder end rib with a modified rudder end rib when you find cracks. Installing the modified rudder end rib terminates the repetitive inspection requirements of AD 68-17-03. Under a licensing agreement with Pilatus, Fairchild Republic Company (also identified as Fairchild Industries, Fairchild Heli Porter, or Fairchild-Hiller Corporation) produced Model PC-6 series airplanes (manufacturer serial numbers 2001 through 2092) in the United States. AD 68-17-03 was intended to apply to all affected serial numbers of Model PC-6 series airplanes listed on Type Certificate Data Sheet (TCDS) No. 7A15, including the Fairchild-produced airplanes. Consequently, this proposed AD would clarify that all models of the PC- 6 airplane on TCDS No. 7A15 (including those models produced under the licensing agreement by Fairchild Republic Company) are included in the applicability. We are proposing this AD to detect and correct cracks in the rudder end rib, which could result in failure of the rudder end rib. This failure could result in loss of directional control.