What was found
CENTER WING BOX UPPER SKIN IS CORRODED IN SEVERAL LOCATIONS AROUND FASTENER HEADS BETWEEN STA 674 THROUGH 696, RBL 43 THROUGH RBL 59, VIEW FROM UNDER CABIN FLOOR BOARDS. REPAIRED CENTER WING BOX UPPER SKIN BS 674 THROUGH 696, RBL 43 THROUGH RBL 59 IAW PRI 540753-14, REV 0-REV 2 AND ER/A 540753-14, REV ORIGINAL ASSOCIATED ER/A 14-540753, ADDED FOR AC 9553.