What was found
MCN - MAJOR REPAIR - DURING AN UNSCHEDULED MAINTENANCE VISIT TO VENDOR REPAIR FACILITY, CORROSION WAS FOUND LT WING UPPER SKIN NEAR WING ROOT AT STR 1A, WBL 150. MAINTENANCE REMOVED CORROSION AND FOUND MATERIAL LOSS TO BE OUT OF LIMITS; BLENDED DAMAGED AREA OF LT WING UPPER SKIN NEAR WING ROOT AND REMOVED STRINGER SEAL PAN AT STR 1A, WBL 150; FABRICATED 2 EACH REPAIR ANGLES, STRINGER SEAL PAN, AND A REPAIR DOUBLER; INSTALLED REPAIR PARTS IAW ER 03-5724-04051-ES1.