A BOEING 737-300 ROLLS RAPIDLY TO THE L DURING NORMAL DSCNT.

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ON JET RTE FROM SAV APCHING THE BITHO 6 ARR INTO MCO ON A 1000 FPM DSCNT THROUGH FL280 ON LNAV AND VERT SPD ENGAGED WITH AUTOPLT ON; ACFT MADE A HARD ROLL TO L. OVERRODE AUTOPLT AT APPROX 30 DEGS L BANK AND ACFT BEGAN TO ROLL BACK R TOWARDS LEVEL FLT. APPARENTLY PRESSURE I APPLIED BEGAN TO RELAX SOMEWHAT AND BEGAN ANOTHER HARD ROLL TO THE L. AT THIS POINT I DISCONNECTED THE AUTOPLT AND THE FO DISCONNECTED THE YAW DAMPER. THE ACFT WAS ROLLED BACK WINGS LEVEL AND CTL WAS RESTORED. SEVERAL MOMENTS LATER I RECONNECTED THE YAW DAMPER AS THERE WERE NO YAW TENDENCIES WHATSOEVER. THE AUTOPLT REMAINED OFF AND I LANDED THE ACFT WITHOUT FURTHER INCIDENT AT MCO. ALTHOUGH SOME PAX WERE STARTLED MOMENTARILY; THE INCIDENT PASSED VERY QUICKLY PER THE FLT ATTENDANTS OBSERVATIONS AND THERE WERE NO INJURIES. ALL PROPER AUTHS WERE NOTIFIED AND APPROPRIATE RPTS HAVE BEEN WRITTEN AND SUBMITTED. AN EXTENSIVE CONFERENCE CALL WAS MADE IMMEDIATELY AFTER THE INCIDENT AND THERE WAS A CONFERENCE HELD AFTER MY RETURN TO PIT THE NEXT DAY. MYSELF AND THE FO WERE ATTENTIVE TO OUR DUTIES DURING THE FLT AND RECOVERY WAS MADE RAPIDLY. THE ENTIRE INCIDENT LASTED; IN MY OPINION AT THE TIME; LESS THEN 5 SECONDS. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTR SAID HE THOUGHT THE CAUSE OF THE PROB WAS AN UNEXPLAINED UNCOMMANDED AUTOPLT ABRUPTLY RAPID L ROLL INPUT. AS PER PROC THE YAW DAMPER WAS IMMEDIATELY AND REFLEXIVELY TURNED OFF BY THE FO AT THE ONSET OF THE ROLL. THIS DID NOT CORRECT THE PROB. THE CAPT FLYING AT THE SAME TIME GRABBED THE WHEEL AND OVER RODE THE AUTOPLT TO BRING THE WINGS LEVEL FROM A 20 TO 30 DEG L BANK. THE AUTOPLT THEREBY DEFAULTED TO CTL WHEEL STEERING. WHEN THE WINGS WERE LEVEL THE CAPT RELAXED HIS PRESSURE ON THE CTL WHEEL WHEREUPON THE AIRPLANE AGAIN COMMENCED ITS ABRUPTLY RAPID L ROLL. THE CAPT DISCONNECTED THE AUTOPLT COMPLETELY AND HAND FLEW THE AIRPLANE. THE REMAINDER OF THE FLT WAS NORMAL WITH THE YAW DAMPER TURNED BACK ON AND THE AUTOPLT LEFT OFF. THERE WERE NO INJURIES; BUT; THE FLT ATTENDANTS AND PAX WERE STARTLED. IF THE RPTR HAD THE EVENT TO HAPPEN AGAIN HE WOULD BE QUICKER ABOUT DISCONNECTING THE AUTOPLT AND MORE ATTENTIVE TO CONSOLING THE PAX AND FLT ATTENDANTS. HE SUGGESTED PLTS BE ENCOURAGED TO PERSONALLY EVALUATE THEIR OWN HAND FLYING CURRENCY TO ASSURE THEIR HAND FLYING PROFICIENCY CONTINUALLY EXISTS. THE FLT DATA RECORDER TAPE WAS READ AND THE AIRPLANE ROLLED TO A BANK ANGLE OF 22 DEGS. THE PF RESPONSE TO THE ONSET OF THE ROLL WAS VIRTUALLY INSTANTANEOUS AS HE WAS 'TWEAKING' (MAKING SMALL ADJUSTMENTS TO) THE THROTTLES AT THE MOMENT OF ONSET OF THE ROLL AND IMMEDIATELY GRABBED THE WHEEL. THERE WAS NO WAKE TURB ENCOUNTER.