What was found
WHILE AIRCRAFT WAS IN HEAVY CHECK MAINTENANCE FOUND THE LEFT SEAT TRACK EXTENSION AT FRAME 87 CORRODED. MAINTENANCE REMOVED AND REPLACED THE LEFT SEAT TRACK EXTENSION AT FRAME 87 IAW EMB 170 SRM 51-41-01, 51-42-01, 51-43-01, 51-21-01, AND 51-23-06. THE AIRCRAFT IS OUT OF SERVICE IN HEAVY CHECK.