What was found
ON A ROUTINE A-CHECK, MAINTENANCE FOUND LEVEL 3 CORROSION AT APPROXIMATELY L/E STA XFS 257 TOP SIDE, LEFT WING. REMOVED FASTENERS, CUT OUT AREAS OF CORROSION, FABRICATED AND INSTALLED DOUBLER FROM 7075-T6.090 AND 2 EACH FILLERS FROM 7075-T6. REPAIRED AND AREA TREATED, PRIMED, AND INSTALLED IAW DER DWG ARW 3216-16.