A CRJ200 IN CLB AT FL280 DECLARED AN EMER AND DIVERTED DUE TO UNCOMMANDED YAW INPUT WITH BOTH YAW DAMPERS AND AUTOPLT DISCONNECTED.

Narrative

ENRTE AND CLBING THROUGH FL200; THE ACFT ENCOUNTERED YAW MOVEMENT L/R TO FOLLOW WITH YAW DAMPER #2 INOP STATUS MESSAGE. THINKING THAT THE YAW DAMPER WAS THE REASON FOR THE ACFT YAW; I RE-ENGAGED YAW DAMPER #2. YAW MOVEMENT WAS IMMINENT UNTIL YAW DAMPER #2 INOP STATUS MESSAGE APPEARED; YAW DAMPER #2 WAS LEFT DISENGAGED. I ASKED THE FO TO CALL MAINT CTL VIA COMPANY RADIO TO DISCUSS THE ISSUE WITH YAW DAMPER #2 AND THE ASSOCIATED YAWING. LEVEL AT FL280 AND THE FO TALKING TO MAINT; YAWING PERSISTED WITH YAW DAMPER #1 ENGAGED. THE ACFT PULLED TO THE R WITH 3 CONSECUTIVE BUMPS. WITH THE CREW MEMBERS' FEET FLAT ON THE FLOOR THE RUDDER PUT ITS OWN DEFLECTION IN AS IF SOMEONE ABRUPTLY PUSHED ON THE RUDDER PEDALS. IT HELD THE PRESSURE IN FOR 20 SECONDS OR MORE. AS I ATTEMPTED TO TRIM THE ACFT; IT WOULD LET GO TO THE NEUTRAL POS. THE AUTOPLT WAS FLYING UP TO THIS POINT. WE ASKED CTR FOR THE MOST DIRECT RTE TO ZZZ1 DUE TO A POSSIBLE PROB WITH THE ACFT. THE FO; STILL IN CONTACT WITH MAINT DESCRIBING THE ISSUE; WAS RECOMMENDED TO DISENGAGE THE YAW DAMPERS ALTOGETHER. THE FO ASKED MAINT TO STAND BY UNTIL ALL WAS COMPLETED. WITH THE YAW DAMPERS AND AUTOPLT DISENGAGED; THE ACFT STILL PULLED TO THE R AND THE PROB WITH THE YAWING WAS INCREASING AS TIME WENT ON. UNABLE TO REMEDY THE PROB AND THE UNCTLABLE INPUT; AN EMER WAS DECLARED WITH ATC TO ZZZ2. MAINT AND DISPATCH WERE ALSO TOLD OF THE EMER AND DIVERSION. THE FLT ATTENDANT WAS ASKED TO RETURN TO HER SEAT DUE TO FEAR OF A FULL RUDDER DEFLECTION AND MOVEMENT OF THE ACFT. SEATBELT SIGN NEVER TURNED OFF. THE QRH WAS PERFORMED FOR THE YAW DAMPER CAUTION MESSAGE IN THE DSCNT. AIRSPD CHANGING; THE PROB CONTINUED (CLB 290 KTS; CRUISE 280 KTS TO 300 KTS AND 250 KTS BELOW 10000 FT). FINAL APCH FLAPS WERE SET TO 45 DEGS AND THE ACFT SEEMED TO BE MORE STABLE WITH LESS MOVEMENT. AN UNEVENTFUL LNDG WAS MADE IN ZZZ2 AND THE PAX DEPLANED THE ACFT. SUPPLEMENTAL INFO FROM ACN 685810: THROUGH FL200; ACFT ENCOUNTERED YAW MOMENT L/R. YAW DAMPER #2 STATUS MESSAGE APPEARED. WHEN YAW DAMPER #2 WAS RE-ENGAGED; YAWING OCCURRED AND YAW DAMPER #2 STATUS MESSAGE RE-APPEARED. YAW DAMPER #2 WAS LEFT DISENGAGED. YAW MOMENT WAS ERRATIC AND UNCOMMANDED FOR PERIODS OF 10 SECONDS OR MORE. LEVEL AT FL280; YAWING PERSISTED. YAW DAMPER #1 WAS DISENGAGED AND YAW PERSISTED. YAW PERSISTED AND AUTOPLT WAS DISENGAGED AND YAW PERSISTED. WE DECLARED AN EMER AND REQUESTED VECTORS TO THE NEAREST ARPT. I MADE THE PA AND SPOKE WITH THE FLT ATTENDANT. WE RAN QRH PROCS. ALL NORMAL CHKLISTS WERE COMPLETED. WE HAD AN UNEVENTFUL LNDG. CALLBACK CONVERSATION WITH RPTR ACN 685812 REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ONLY MAINT ACTION RPTED WAS SECONDHAND INFO FROM A LEAD TECHNICIAN THAT INDICATED THAT ONLY THE #2 YAW DAMPER ACTUATOR WAS REPLACED. THE RPTR INDICATED THERE MUST HAVE BEEN MORE WRONG WITH THE RUDDER SYS AS THE YAW DAMPERS AND THE AUTOPLT WAS DISCONNECTED. CALLBACK CONVERSATION WITH RPTR ACN 685810 REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE YAW CTL INPUTS IS UNKNOWN AS MAINT DID NOT RPT ANY FIX OR ACTION TAKEN.