Airworthiness Directives; Air Tractor, Inc. Models AT-502, AT-502A, AT-502B, and AT-503A Airplanes

This amendment supersedes Airworthiness Directive (AD) 2002- 11-03, which applies to certain Air Tractor, Inc. (Air Tractor) Models AT-502, AT-502A, AT-502B, and AT-503A airplanes. AD 2002-11-03 lowered the safe life for the wing lower spar cap and further reduced the safe life for airplanes that incorporate or have incorporated Marburger Enterprises, Inc. winglets. AD 2002-11-03 also currently requires you to eddy-current inspect the wing lower spar cap immediately prior to the replacement/modification to detect and correct any crack in a bolthole before it extends to the modified center section of the wing and report the results of this inspection to the Federal Aviation Administration (FAA). Field inspections on the affected airplanes have revealed wings with cracks below the currently established safe life. This AD would further reduce the safe life of the Models AT502, AT- 502B, and AT-503A airplanes and would add airplanes recently manufactured to the Applicability of the AD. The actions specified by this AD are intended to prevent fatigue cracks from occurring in the wing lower spar cap before the 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.