Summary
The FAA proposes to revise an earlier proposed airworthiness directive (AD) that applies to certain Air Tractor, Inc. (Air Tractor) Models AT-502, AT-502A, AT-502B, and AT-503A airplanes, which proposes to supersede AD 2002-26-05. AD 2002-26-05 lowers the safe life for the wing lower spar caps for Models AT-502, AT-502A, AT-502B, and AT-503A airplanes and those that incorporate or have incorporated Marburger Enterprises, Inc. (Marburger) winglets. AD 2002-26-05 also requires you to eddy-current inspect the wing lower spar caps immediately before modifying to correct any crack in a bolt hole before it extends to the modified center section of the wing and report the results of the inspection to the FAA if cracks are found. AD 2002-11-05 R1 currently requires similar action on Model AT-501 airplanes. Since issuing the earlier NPRM, we determined that Model AT-501 airplanes should be added to the Applicability section of this proposed AD and that this proposed AD should also supersede AD 2002-11-05 R1. We have revised the alternative method of compliance (AMOC) to include inspection procedures for airplanes that have or have had Marburger winglets installed. We have also updated the safe life of the replacement and new production spar cap based on additional data we have received from the manufacturer. Since these actions impose an additional burden over that proposed in the earlier NPRM, we are reopening the comment period to allow the public the chance to comment on these additional actions.