What was found
FLIGHT 6455 ATL TO MLI, ON DEPARTURE SELECTING FLAPS UP, CREW RECEIVED AN EICAS MESSAGE "SLAT FAIL." CREW CONFIRMED VISUALLY THAT THE SLATS WERE NOT IN THE RETRACTED POSITION, RAN THE QRH CHECKLIST AND RETURNED TO ATL. REMOVED AND REPLACED NR 2 AND NR 3 SLAT SKEW SENSOR RT WING. RIGGED ELECTRICALLY AND OPS CK GOOD.