What was found
DURING HEAVY CHECK MAINTENANCE FOUND CORROSION ON CENTER FUSELAGE III FLOOR SUPPORT STRUCTURE, MID SHEAR PANEL AT FR 87, BL 0. CENTER FUSELAGE III FLOOR SUPPORT STRUCTURE AT FR 87, BL 0 REPLACED WITH NEW MID SHEAR PANEL, IAW SRM 51-42-01. A/C REMAINS IN CHECK.