A PRM1 CAPTAIN REPORTED EXPERIENCING UNCOMMANDED PITCH; ROLL; AND YAW AFTER TAKEOFF. FLT CREW DECLARED AN EMERGENCY AND RETURNED TO THE DEP ARPT.

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UNCOMMANDED PITCH; ROLL AND YAW. UNABLE TO ARREST UNCOMMANDED INPUTS OR CORRECT UNCOORDINATED FLT CONFIGURATION WITH ANYTHING OTHER THAN REDUCTION OF THRUST TO REDUCE FORCES ON PRIMARY FLT CONTROL SURFACES. IT TOOK THE FULL STRENGTH OF BOTH PLTS TO CONTROL THE ACFT. WHEN THE ACFT SLOWED DOWN FROM THE THRUST REDUCTION; ONLY THEN WERE WE ABLE TO BEGIN TO REGAIN CONTROL. WE LANDED WITH FULLY DEFLECTED RUDDER AND VERY LITTLE PITCH CONTROL USING EXTREME FORCE BY PILOTS ON THE CONTROL YOKE. EMER WAS DECLARED; DOWNWIND LANDING MADE WITH MEN AND EQUIP DISPATCHED. EMER BEGAN AFTER A NORMAL PREFLT; PRE-TAXI CHKS AND NORMAL TAKEOFF TO APPROX 5500 FT MSL.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED MAINTENANCE HAS NOT YET FOUND A CAUSE OF THE FLIGHT CONTROL ANOMALY; AND IS CONTINUING TO TROUBLESHOOT THE FLIGHT CONTROL COMPUTERS AND THE AUTOPILOT SERVOS. THE PRIMARY PROBLEM THE REPORTER FACED IN FLIGHT WAS THE FULL UNCOMMANDED DEFLECTION OF THE RUDDER; WHICH REQUIRED THE FULL STRENGTH OF THE REPORTER AND THE FIRST OFFICER TO OVERCOME.