What was found
MCN - MAJOR REPAIR - DURING C-17 CHECK, CORROSION WAS FOUND ON UPPER AND LOWER SURFACE OF FLOORBEAM UPPER CHORD AT BS 328, FROM BL "0" TO RBL 53. MAINTENANCE REMOVED CORRODED SECTION OF FLOORBEAM UPPER CHORD AT BS 328, FROM BL "0" TO RBL 53; FABRICATED A NEW REPLACEMENT SECTION OF UPPER CHORD PER DWG 65-45812; INSTALLED REPAIR PART IAW B737-300 SRM 51-40-02, FIG 8 AND 12.