What was found
AT D-CHECK, CRACKS WERE FOUND IN THE J-BEAM WHICH IS ATTACHED TO THE AFT FACE OF THE AFT PRESSURE BULKHEAD. THE CRACKS ORIGINATE IN THE RADII ADJACENT TO ATTACH BOLTS APPROX 1 INCH EACH SIDE OF THE ACFT CENTERLINE. THE CRACKS APPEAR TO OCCUR UNDER NORMAL OPERATING CONDITIONS AND ARE POSSIBLY CAUSED BY THE COMBINED FORCES OF CABIN PRESSURE AGAINST THE FRONT FACE OF THE BULKHEAD AND TENSION FROM THE 13 FLIGHT CONTROL CABLES WHICH ARE ROUTED THROUGH PULLEYS ATTACHED TO THE J-BEAM. SUBMITTER RECOMMENDED THE FOLLOWING: PERFORM PERIODIC INSPECTIONS OF ALL DC-8 ACFT WITH FLAT AFT PRESSURE BULKHEADS, AND, REPAIR CRACKS PER DC-8 SRM 53-2-5, FIG 26.