THE BOEING 737-400 MADE AN UNCOMMANDED R ROLL AND AFTER AUTOPLT DISCONNECT THE R ROLL TENDENCY PERSISTED AND HAD TO BE OFFSET WITH COMMENSURATE L AILERON TO MAINTAIN WINGS LEVEL AND ADDITIONAL AILERON TO TURN TO THE L.

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HAZY LOW SCUD IN RIC AREA -- REFUSED VISUAL AND VECTORED FOR VOR/DME 20 180 DEGS INBOUND LEG 1700 FT AT OBERG FAF VISIBILITY 7 MI BELOW SCUD LAYER. HAND FLEW ACFT UNTIL 8000 FT MSL EXTENDED FLAPS TO 5 DEGS 17 KIAS RECOUPLED AUTOPLT; SLIGHT DSCNT TO 1700 FT TO INTERCEPT INBOUND LEG PRIOR TO OBERG. USED LNAV WITH VOR RAW DATA ON FO SIDE. A CHANNEL USED ON AUTOPLT UPON INTERCEPT. RADAR AUTOPLT ON ACFT ROLLED R RAPIDLY; DISCONNECTED AUTOPLT; CONTINUED TO ROLL R AS WHEEL STAYED DEFLECTED. HAD TO HOLD 1/2 WHEEL THROW L TO KEEP WINGS LEVEL AND MORE TO TURN L. DISCONNECTED YAW DAMPER; NO CHANGE; REENGAGED NO CHANGE RUDDER ZERO DEG DEFLECTION PRIOR TO INITIAL AUTOPLT ENGAGEMENT ACFT IN TRIM LATERALLY; LONGITUDE; AND PITCH. ONLY 1 MEL (APU INOP); GOOD TRIMMING ACFT. RUDDER TRIM .005 LEFT OF CTR; COMPLETED LAND CHK LIST; CLRED TO LAND; 40 DEGS FLAPS DUE TO 6607 FT RWY 20 RUN-UP; 89 DEG TEMP NO TURB OR XWIND. DID NOT HAVE TIME TO DECLARE EMER FINAL LNDG. PHASE -- LANDED WITHOUT INCIDENT. SPOILER DEPLOYED NORMALLY AND ALSO CYCLED THEM ON APCH TO SEE IF ANY SPOILER FLOAT -- NONE. AFTER TAXI-IN AND ENG SHUTDOWN THE CTL WHEEL WAS DEFLECTED 3 1/2 UNITS R. OUTSIDE ACFT FLT SPOILERS UP APPROX 10 DEGS R SIDE AND R AILERON UP 1 1/2 INCHES ABOVE FLARED POS. ALSO TRIED OPPOSITE AILERON TRIM NO CHANGE IN CTL WHEEL OR PRESSURE. TAXI-IN NO NOSEWHEEL DEFLECTION -- NORMAL AND ENGS WERE SYMMETRICAL ON APCH; FLAPS EVEN; AND FUEL TANKS QUANTITY INDICATED WITHIN 10 LBS OF EACH OTHER. NO OPINIONS OTHER THAN ONCE AUTOPLT DISCONNECTED; 'INCREASING' ROLL RATE STOPPED AT LAST AMOUNT PRIOR TO DISCONNECT; APPROX 30 DEGS BANK R. ALSO DEPLOYED SPD BRAKES TO CHK FOR FLT SPOILER FLOAT -- NONE. GND SPOILERS DEPLOYED NORMALLY ON GND. AT NO TIME DID I LOSE CTL OF ACFT. AFTER ROLL TO R WAS STOPPED AND RWY IN SIGHT DID NOT MAKE ANY LARGE CTL INPUTS; HELD WHAT I HAD. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTR SAID HE WAS FLYING A B737-400. HE HAD HIS FEET ON THE RUDDER PEDALS BUT SEEMED UNSURE WHETHER HE WAS APPLYING RUDDER PRESSURE. THE RPTR BELIEVES THE CAUSE OF THE PROB WAS THE AUTOPLT DID NOT TOTALLY DISENGAGE. THE RPTR DISENGAGED THE AUTOPLT 3 TIMES RECYCLING THE AUTOPLT ENGAGE DISENGAGE PADDLES ON AND OFF 3 TIMES. HE DID TURN OFF THE YAW DAMPER AND THERE WAS NO ABNORMAL RESPONSE. THE MECHS STATED THE FLT RECORDER SHOWED THE AUTOPLT WAS TURNED ON MOMENTARILY ON THE GND TAXIING IN. NO ONE TURNED ON THE AUTOPLT. THE RPTR SUGGESTED THAT PRACTICE OCCUR IN TRIMMING AND CROSS CTLING IN THE SIMULATOR CURRICULUM TRAINING SO THE PLT WOULD RECOGNIZE MORE READILY ASYMMETRICAL ENG PWR OR DRAG TO COMPENSATE APPROPRIATELY.