Airworthiness Directives; Air Tractor, Inc. AT-400, AT-500, and AT-800 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 2000- 14-51, which requires inspection of the wing lower spar cap for cracks on Air Tractor, Inc. (Air Tractor) Models AT-501, AT-502, and AT-502A airplanes, and modification or replacement of any cracked wing lower spar cap. This AD lowers the safe life for the wing lower spar cap on Air Tractor AT-400, AT-500, and AT-800 series airplanes. This AD is the result of numerous reports of cracks in the \3/8\-inch bolthole of the wing lower spar cap on the affected airplanes. The actions specified by this AD are intended to prevent fatigue cracks from occurring in the wing lower spar cap before the originally established safe life is reached. Fatigue cracks in the wing lower spar cap, if not detected and corrected, could result in the wing separating from the airplane during flight.