What was found
(CAN) WHILE CARRYING OUT THE SEB 97-1 AFT DOORPOST INSPECTION, CRACKS WERE NOTED AT THE SUBJECT AREAS ON BOTH DOORPOSTS (IPC "CHANNEL-BULKHEAD"). SUBMITTER SUSPECTS THAT TAXIING OVER ROUGH SURFACES, OR POSSIBLY HARD OR CRABBED LANDINGS, CONTRIBUTES TO THE FLEXING OF THE BULKHEAD THAT RESULTS IN THE CRACKING. CRACKS ARE FOUND BY LOOKING WITH LIGHT AND MIRROR FORWARD NEAR THE AILERON CABLE PULLEY AT THE BOTTOM OF THE AFT DOORPOSTS. THE CRACK RADIATES FROM THE RELIEF CUTOUT WHERE THE INSIDE FLANGE OF THE BULKHEAD CHANGES FROM VERTICAL TO HORIZONTAL. (TC NR 20071128010)