What was found
WHILE AIRCRAFT WAS IN HEAVY CHECK MAINTENANCE FOUND THE LEFT FLOOR SILL AFT OF FRAME 19 CORRODED. MAINTENANCE REMOVED AND REPLACED THE LEFT FLOOR SILL PLATE AFT OF FRAME 19 IAW EMB 170 SRM 51-40-02, 51-41-02, AND 51-43-03. THE AIRCRAFT IS OUT OF SERVICE IN HEAVY CHECK.