Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP)
Troubleshooting; Human-Machine Interface; Situational Awareness
Aircraft Equipment Problem Critical; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem
Aircraft; Weather
During cruise flight at FL290 with the First Officer flying; we received an EICAS 'AP TRIM IS LWD [Left Wing Down]' Caution message. While complying with the QRH our filed route required a left turn. We realized when the First Officer disengaged the autopilot; that the ailerons were jammed. The aircraft continued to fly straight ahead and we were unable to make the turn to the left. I was in disbelief and took control of the jet. I immediately recognized that the jet was unresponsive in the roll axis and requested present heading from ATC to deal with the issue. The controls felt as if the autopilot had not completely disengaged so I applied slightly greater force to the yoke and was able to regain unrestricted movement of the flight controls.  We were then cleared direct to our filed destination. As we reviewed the QRH for the autopilot as well as the aileron system jammed it led us to believe that our ailerons may have actually been frozen due to ice since we had departed in very wet conditions. The runways were wet and there was heavy rain for most of the first half of our enroute climb. The OAT at FL290 was -35C. We did discuss a precautionary landing but we determined it would have taken about the same amount of time to make a normal descent rate into our destination. The weather was better and; the runway is longer; the winds down the runway as opposed to a shorter; wet runway with a quartering crosswind. The flight controls were responding normally throughout the last 20 minutes of our flight so we discussed--if the controls did give us more issues on our descent and landing--it would be safer to deal with it under VFR conditions. The jet flew normally and we landed without incident. We completed a maintenance write-up upon arrival at our destination.I'm not certain what the final determination of the flight control issue was but if it was indeed possible frozen contaminates restricting movement of the ailerons there should probably be a procedure put back into place that requires exercising the ailerons when departing under certain conditions to try and prevent anything freezing to any mechanical linkages or surfaces that could restrict movement. The only thing I would do differently would be to simply advise ATC that we had had a brief flight control issue but everything had been resolved.
[Report narrative contained no additional information]
When they received an EICAS 'AP TRIM IS LWD [Left Wing Down]' message a CRJ-200 flight crew discovered they could not utilize ailerons to roll the aircraft.  After applying greater force to the controls; however; they regained full control.  They speculate that; as a result of heavy rains during the climb into freezing conditions; the ailerons had been immobilized by frozen water and; once sufficient force was applied; the restriction was eliminated.  Maintenance continued to investigate.