What was found
FLIGHT 1845, PHL-FPO - THE CREW RECEIVED A SLAT FAIL WITH SLAT DEPLOYED TO UNKNOWN POSITION MESSAGE. THE CREW FOLLOWED THE QRH AND WAS UNABLE TO CLEAR THE ITEM. THE CREW DECIDED TO RETURN TO THE FIELD,PHL, AND CALLED EMERGENCY EQUIPMENT OUT AS A PRECAUTIONARY MESSURE. THE FLIGHT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE COULD NOT CONFIRM THE FAULTS. THE SLATS 2/3 AND 3/4 SKEW SENSORS WERE REPLACED AS A PRECAUTION AND ALSO SLAT 2/3 AND 3/4 SKEW SENSOR HARNESSES.