The FAA proposes to adopt a new airworthiness directive (AD) for all Air Tractor Inc. (Air Tractor) Models AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-503, AT-503A, AT-504, AT-602, AT-802, and AT-802A airplanes. This proposed AD was prompted by reports of cracks in the flap torque tube actuator attachment brackets that may cause the flap actuator to detach from the flap torque tube. For more information on the proposed AD, see the Federal Register announcement here.
There are differences between this proposed AD and Air Tractor Service Letter 347: Air Tractor SL #347, Rev A, provides an allowance (plus or minus 15%) for the 300-hour visual inspections, and this proposed AD would not. Air Tractor SL #347, Rev A, specifies performing the dye penetrant inspection within 900 hours time-in-service (TIS), and this proposed AD would require the initial dye penetrant inspection within 300 hours TIS. Air Tractor SL #347, Rev A, specifies replacing a cracked torque tube, while this proposed AD would require replacing a cracked torque tube with a torque tube that has zero hours TIS. Air Tractor SL #347, Rev A, specifies reporting any cracked welds identified during the inspections to Air Tractor, and this proposed AD would not.