Summary
This document proposes to supersede AD 95-20-06, which currently requires inspecting the front spar attachment lugs and the rear spar for fatigue cracks and modifying the vertical fin if cracks are found. If no cracks are found, continue repetitively inspecting the area until cracks are found; and then incorporate the modification as a terminating action. The proposed action would retain the actions required in AD 95-20-06 for all Air Tractor models that have a \3/16\- inch fin front spar fitting. Air Tractor models that are fitted with a \1/4\-inch fin front spar fitting would not be required to accomplish this action. This action is prompted by two incident reports involving the failure of the front and rear spar attachment of the vertical fin. The actions specified by this AD are intended to prevent in-flight vertical fin structural failure of the front spar attachments and eventually the rear spar attachment, which, if not detected and corrected, could result in loss of directional control and loss of control of the airplane.