Narrative:

We were about 6000 ft on a left downwind. Weather was few clouds about 10;000 ft or so. Captain was flying. We were cleared for a visual approach and cleared to a lower altitude. Captain disengaged the autoplt to hand fly. As she tried to roll the aircraft to level out; she said she was unable to move the control yoke to make the aircraft roll. She asked if I had the same problem; I did. We had pitch but didn't have roll. We were discussing pulling the roll disconnect; when we heard a loud pop and had full control of the controls. Entire episode lasted approximately 5 second or so. At no time did we have any caution or warning lights. We were already cleared for the visual; about to turn base; within sight of the field; and #1 for the airport. We did not declare an emergency. We had a successful landing with no other problems. Maintenance was notified and aircraft was grounded.callback conversation with reporter revealed the following information: reporter stated that they had pitch control but roll control was frozen. It was speculated that even though cockpit indications verified autopilot disconnect; the roll function remained engaged until sufficient force was applied to the yoke. Maintenance could not duplicate the malfunction. After all flight control components were inspected; autopilot computer was replaced as a precautionary measure.

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Original NASA ASRS Text

Title: DASH 8 ROLL CONTROL FUNCTION FROZE AFTER DISCONNECTING AUTOPILOT. FLT CREW WAS ABLE TO OVERPOWER ANOMALY AND CONTROL WAS REGAINED.

Narrative: WE WERE ABOUT 6000 FT ON A LEFT DOWNWIND. WEATHER WAS FEW CLOUDS ABOUT 10;000 FT OR SO. CAPT WAS FLYING. WE WERE CLEARED FOR A VISUAL APPROACH AND CLEARED TO A LOWER ALTITUDE. CAPT DISENGAGED THE AUTOPLT TO HAND FLY. AS SHE TRIED TO ROLL THE AIRCRAFT TO LEVEL OUT; SHE SAID SHE WAS UNABLE TO MOVE THE CONTROL YOKE TO MAKE THE AIRCRAFT ROLL. SHE ASKED IF I HAD THE SAME PROBLEM; I DID. WE HAD PITCH BUT DIDN'T HAVE ROLL. WE WERE DISCUSSING PULLING THE ROLL DISCONNECT; WHEN WE HEARD A LOUD POP AND HAD FULL CONTROL OF THE CONTROLS. ENTIRE EPISODE LASTED APPROX 5 SEC OR SO. AT NO TIME DID WE HAVE ANY CAUTION OR WARNING LIGHTS. WE WERE ALREADY CLEARED FOR THE VISUAL; ABOUT TO TURN BASE; WITHIN SIGHT OF THE FIELD; AND #1 FOR THE AIRPORT. WE DID NOT DECLARE AN EMERGENCY. WE HAD A SUCCESSFUL LANDING WITH NO OTHER PROBLEMS. MAINT WAS NOTIFIED AND ACFT WAS GROUNDED.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THAT THEY HAD PITCH CONTROL BUT ROLL CONTROL WAS FROZEN. IT WAS SPECULATED THAT EVEN THOUGH COCKPIT INDICATIONS VERIFIED AUTOPILOT DISCONNECT; THE ROLL FUNCTION REMAINED ENGAGED UNTIL SUFFICIENT FORCE WAS APPLIED TO THE YOKE. MAINT COULD NOT DUPLICATE THE MALFUNCTION. AFTER ALL FLT CONTROL COMPONENTS WERE INSPECTED; AUTOPILOT COMPUTER WAS REPLACED AS A PRECAUTIONARY MEASURE.

Data retrieved from NASA's ASRS site as of January 2009 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.