Summary
We propose to supersede Airworthiness Directive (AD) 2003-13- 04, which applies to Pilatus Aircraft Ltd (Pilatus) Model PC-6 airplanes, all manufacturer serial numbers (MSN) up to and including 939. AD 2003-13-04 currently requires you to inspect the integral fuel tank wing ribs for cracks and the top and bottom wing skins for distortion, repair any cracks or distortion before further flight, and do a fuel tank ventilating system installation. Since we issued AD 2003-13-04, the FAA determined the action should also apply to all the models of the PC-6 airplanes listed in the type certification data sheet of Type Certificate (TC) No. 7A15 that are produced in the United States through a licensing agreement between Pilatus and Fairchild Republic Company (also identified as Fairchild Industries, Fairchild Heli Porter, or Fairchild-Hiller Corporation). In addition, the intent of the applicability of AD 2003-13-04 was to apply to all the affected serial numbers of the airplane models listed in TC No. 7A15. Consequently, this proposed AD would retain all the actions of AD 2003- 13-04, would add those Fairchild Republic Company airplanes to the applicability of this proposed AD, and would list out the individual specific airplane models. We are proposing this AD to detect and correct cracks in the ribs of the inboard integral fuel tanks in the left and right wings, which could lead to wing failure during flight.