What was found
AIRCRAFT RETURNED TO PLATFORM DUE TO DURING TAKEOFF ROLL, THE MESSAGE SLAT SECONDARY FAIL AND CONFIGURATION ALARM WERE SHOWED WITH A SLAT SPLIT INDICATION AND SHIP SPEED WAS ALMOST CERO. MAINTENANCE PERSONNEL PERFORMED THE FLAP / SLAT OPERATION CHECK IAW FIM 27-80-F1-70A-421A, DETECTING THE SLAT SECONDARY WITH FAIL; SO THE SLAT SECONDARY WITH FAIL MESSAGE WAS DEFERRED IAW MEL 27-80 CAT C. AT MEX, THE BACKUP ELECTRIC MOTOR BRAKE WAS REPLACED IAW AMM DMC-B787A-27-81-34-00A-520A-A AND AMM DMC-B787A-27-81-34-00A-720A-A, ALL TESTED CORRECT AND THE REPORT WAS CLOSED.