What was found
FLAPS WOULD NOT EXTEND FOR LANDING. THE APPROACH WAS DISCONTINUED AND AN EMERGENCY WAS DECLARED. THE CREW PERFORMED QRH PROCEDURES AND WAS ABLE TO EXTEND THE LEADING EDGE SLATS USING THE ALTERNATE FLAPS SYSTEM. THE TRAILING EDGE FLAPS REMAINED FULLY RETRACTED. THE FLIGHT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REMOVED AND REPLACED NR 3 FLAP SKEW SENSOR. OPERATIONALLY CHECKS OK PER FIM 27-59-00. THE AIRCRAFT WAS GROUNDED.