What was found
WHILE AIRCRAFT WAS IN HEAVY CHECK MAINTENANCE FOUND THE LEFT FF1 FORWARD SEAT TRACK EXTENSION CORRODED FRAME 12L TO 20L. MAINTENANCE REMOVED AND REPLACED THE FF1 FORWARD SEAT TRACK EXTENSION IAW EMB 170 SRM 51-41-01, 51-41-02, 51-43-03, AND 51-43-04. THE AIRCRAFT IS OUT OF SERVICE IN HEAVY CHECK.