CL65 FO LANDED LONG DURING AN EMER DIVERSION TO ANOTHER ARPT DUE TO AILERON CTL PROB.

Narrative

AT FL280; WE GOT AN AUTOPLT TRIM L WING DOWN CAUTION MESSAGE FOR A COUPLE OF SECONDS; THEN AN AUTOPLT TRIM R WING DOWN CAUTION MESSAGE. BRIEFLY THEN AN AUTOPLT TRIM L WING DOWN MESSAGE FOR A COUPLE OF SECONDS. THEN ANOTHER AUTOPLT TRIM R WING DOWN MESSAGE PERSISTED. WE RAN THE ABNORMAL CHKLIST. ONE IS TO DISCONNECT THE AUTOPLT. THE FO WHO WAS FLYING NOTED THE AILERONS WERE EXTREMELY STIFF AND DIFFICULT TO MOVE. IT TOOK EXCESSIVE PRESSURE ON THE CTL INPUTS TO TURN THE ACFT. THE ELEVATOR AND RUDDER OPERATED NORMALLY. WE CONTACTED MAINT. THEY WERE UNABLE TO DETERMINE A CAUSE OR A SOLUTION WHILE AIRBORNE. WE DECIDED TO DIVERT TO IAD. WE TALKED TO DISPATCH ABOUT THE WINDS AT IAD (WHICH WERE CALM). THE FLT ATTENDANT WAS NOTIFIED OF THE SIT AND THE PAX WERE BRIEFED. WE LANDED AT IAD WITHOUT INCIDENT. THE ACFT WAS FLOWN BY HAND AFTER THE MALFUNCTION WAS DISCOVERED. SUPPLEMENTAL INFO FROM ACN 522142: THE FO LANDED LONG AS HE HAD AILERON FLT CTL PROBS. I GOT THE MORE EXPERIENCED PLT TO LAND IN AN EMER LNDG. HE WAS DOING FINE UNTIL HE TRIED TO SETTLE THE ACFT ON SMOOTHLY BUT IT FLOATED.