What was found
FUSELAGE SKIN IS CRACKED AT CHEM-MILL, BELOW STR 23R, STA 727E +2". REQUIRES INTERNAL NDT IAW FIG 4 OF GENERATING TC AFTER ACCESSED. ACFT GROUNDED. REPAIRED FUSELAGE SKIN IAW SRM 53-00-01, REP 31. THIS REPAIR IS A CAT B REPAIR WITH INSPECTION THRESHOLD OF 66,000 FLT CYCLES OR 12,000 FLT CYCLES AFTER REPAIR INSTALLATION. ACFT FLT CYCLES AT TIME OF REPAIR 47,209.