What was found
REPORTED CORROSION ON THE MAIN DECK FLOORBEAM UPPER T-CHORD HORIZONTAL FLANGE AT STA 500 BETWEEN APPROXIMATELY LBL 50.0 AND LBL 60.0. THE UPPER CHORD WAS REPLACED WITH SPLICES AT LBL 21.37.5 AND LBL 78.5, SIMILAR TO 747 SRM 53-10-07 FIG 12. REPAIR ACCOMPLISHED AS PER BOEING MESSAGE 1-182888881 AND FAA FORM 8100-9. SUPPLEMENTAL INSPECTION REQUIRED FOR EVERY C-CHECK OR 24 MONTHS WHICH EVER OCCURS EARLIER.