Airworthiness Directives; Air Tractor Incorporated Models AT-301, AT-401, and AT-501 Airplanes

This amendment adopts a new airworthiness directive (AD) that applies to certain Air Tractor Incorporated (Air Tractor) Models AT- 301, AT-401, and AT-501 airplanes that are equipped with a \3/16\-inch thick aluminum fin front spar fitting and an all metal rudder. This AD requires that you repetitively inspect the vertical fin front spar attachment fittings for fatigue cracks, and rework the vertical fin if any cracks are found. This AD is the result of reports of a vertical fin front spar fitting failure on a Model AT-401 airplane. The actions specified by this AD are intended to detect and correct cracks in the vertical fin front spar attachment fittings, which could result in failure of the vertical fin. This condition could lead to loss of directional control and eventual loss of airplane control.