What was found
(AIRCRAFT NOT GROUNDED) (DEFECT DISCOVERED DURING AC HEAVY MX VISIT) REAR FUSELAGE CABIN FLOOR STRUCTURE, CORROSION FOUND ON LONGITUDINAL BEAM AT Y599.5 BTW FR68-R69. CABIN FLOOR STRUCTURE, LONGITUDINAL BEAM AT Y599.5 BTW FR68-FR70 REPLACED AS PER SRM 51-72-11-911-001 AND SRM 51-42-11 REV.158.