Narrative:

Yet another anomaly within an aircraft, which should have sufficient checks and balances to avoid a safety of flight condition, such as this condition. Hopefully, intervention and investigation will prevent a fatal accident. The aircraft departed on a 25 min flight at night. WX was VMC with light xwinds and scattered clouds at intermediate altitudes between surface and cruise flight level. The captain (PF) noted that the 'feel' of the aircraft seemed unusual on takeoff. He felt that it was not 'tracking' normally. After takeoff, the departure called for a left turn to a heading roughly 90 degrees left of the runway heading. The captain selected autoplt at approximately 3000 ft MSL. As the aircraft climbed through 8800 ft at approximately 240 KIAS, the aircraft suddenly rolled left to an attitude of 35 degrees leeward. The captain grabbed the yoke and reversed the role, simultaneously disconnecting the autoplt. He stated it required about 60-65 degrees of rearward yoke to hold wings level. He directed the first officer to squawk emergency, declare an emergency, and request emergency return to the airport of origin. Both pilots scanned the FMS for warnings and/or alerts. They observed none. The captain's first thought was that he had experienced an engine failure. Scanning the secondary engine and confign displays, the pilots noted nothing unusual. On the first officer, the captain saw aileron and stabilizer deflections corresponding to his flight condition. He noted no indications of a 'floating spoiler.' the first officer offered to apply trim to counteract the control forces. The captain accepted a slight amount, but was concerned that too much trim might mask or aggravate the situation. He was able to maintain a right turn at 10 degree angle of bank to reverse course, but felt a left turn would be unpredictable. The captain accepted a slight downwind component to expedite landing. Confign was normal to gear down/flaps 25 degrees. Feeling that a full flap landing would be safer for the conditions, he instructed the first officer to lower flaps to 40 degrees in small increments and be ready to return to the previous setting if ctlability problems ensued. The landing was uneventful.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.