What was found
TOOK OFF FROM RUNWAY 30, TAKEOFF NORMAL AT 400 FT, V2 + 20 SELECTED FLAPS ZERO. FLAPS STAYED AT 15 DEGREES. CLIMBED TO 4000 FT MSL. ATTEMPTED TO IDENTIFY PROBLEM AND FOUND FLAPS WOULD NOT EXTEND PAST 15 DEGREES. CONTACT TOWER AND ASKED FOR LONGEST RUNWAY. TOWER DECLARED EMERGENCY UNREQUESTED BY FLT CREW. LANDED WITHOUT INCIDENT. MAINTENANCE DISCOVERED INTERMITTENT FAILURE OF THE FLAP DRIVE MOTOR. FLAP DRIVE MOTOR/GEAR REDUCTION UNIT REPLACED IAW MM 27. OPERATIONS CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.