A B717 IN CLB AT 8800 FT DECLARED AN EMER AND DIVERTED DUE TO THE AUTOPLT DISCONNECTING AND SUDDEN L ROLL TO 35 DEGS L WING DOWN. NEEDED 65 DEGS R WING DOWN YOKE FOR LEVEL FLT. CAUSED BY RUNAWAY AILERON TRIM WITHOUT COCKPIT WARNING.

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YET ANOTHER ANOMALY WITHIN AN ACFT; WHICH SHOULD HAVE SUFFICIENT CHKS AND BALS TO AVOID A SAFETY OF FLT CONDITION; SUCH AS THIS CONDITION. HOPEFULLY; INTERVENTION AND INVESTIGATION WILL PREVENT A FATAL ACCIDENT. THE ACFT DEPARTED ON A 25 MIN FLT AT NIGHT. WX WAS VMC WITH LIGHT XWINDS AND SCATTERED CLOUDS AT INTERMEDIATE ALTS BTWN SURFACE AND CRUISE FLT LEVEL. THE CAPT (PF) NOTED THAT THE 'FEEL' OF THE ACFT SEEMED UNUSUAL ON TKOF. HE FELT THAT IT WAS NOT 'TRACKING' NORMALLY. AFTER TKOF; THE DEP CALLED FOR A L TURN TO A HDG ROUGHLY 90 DEGS L OF THE RWY HDG. THE CAPT SELECTED AUTOPLT AT APPROX 3000 FT MSL. AS THE ACFT CLBED THROUGH 8800 FT AT APPROX 240 KIAS; THE ACFT SUDDENLY ROLLED L TO AN ATTITUDE OF 35 DEGS LEEWARD. THE CAPT GRABBED THE YOKE AND REVERSED THE ROLE; SIMULTANEOUSLY DISCONNECTING THE AUTOPLT. HE STATED IT REQUIRED ABOUT 60-65 DEGS OF REARWARD YOKE TO HOLD WINGS LEVEL. HE DIRECTED THE FO TO SQUAWK EMER; DECLARE AN EMER; AND REQUEST EMER RETURN TO THE ARPT OF ORIGIN. BOTH PLTS SCANNED THE FMS FOR WARNINGS AND/OR ALERTS. THEY OBSERVED NONE. THE CAPT'S FIRST THOUGHT WAS THAT HE HAD EXPERIENCED AN ENG FAILURE. SCANNING THE SECONDARY ENG AND CONFIGN DISPLAYS; THE PLTS NOTED NOTHING UNUSUAL. ON THE FO; THE CAPT SAW AILERON AND STABILIZER DEFLECTIONS CORRESPONDING TO HIS FLT CONDITION. HE NOTED NO INDICATIONS OF A 'FLOATING SPOILER.' THE FO OFFERED TO APPLY TRIM TO COUNTERACT THE CTL FORCES. THE CAPT ACCEPTED A SLIGHT AMOUNT; BUT WAS CONCERNED THAT TOO MUCH TRIM MIGHT MASK OR AGGRAVATE THE SIT. HE WAS ABLE TO MAINTAIN A R TURN AT 10 DEG ANGLE OF BANK TO REVERSE COURSE; BUT FELT A L TURN WOULD BE UNPREDICTABLE. THE CAPT ACCEPTED A SLIGHT DOWNWIND COMPONENT TO EXPEDITE LNDG. CONFIGN WAS NORMAL TO GEAR DOWN/FLAPS 25 DEGS. FEELING THAT A FULL FLAP LNDG WOULD BE SAFER FOR THE CONDITIONS; HE INSTRUCTED THE FO TO LOWER FLAPS TO 40 DEGS IN SMALL INCREMENTS AND BE READY TO RETURN TO THE PREVIOUS SETTING IF CTLABILITY PROBS ENSUED. THE LNDG WAS UNEVENTFUL.