Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP)
Confusion; Human-Machine Interface
Aircraft Equipment Problem Critical
Aircraft Equipment Problem Dissipated; Flight Crew Became Reoriented; General Maintenance Action
Aircraft; Manuals
In level flight at 17;000 feet we were given direct to our first fix which was approximately 60 degrees to our right. The First Officer was flying and the Autopilot was on. The autopilot had initiated a right turn towards the fix when we received a rather violent movement further to the right as though someone had slammed on the right rudder. Upon realizing that it was from neither I nor the First Officer's input I called for and assumed control of the aircraft. I performed the memory items for an uncommanded yaw motion and called for the appropriate checklist followed by the appropriate QRH. In looking at ED 1 and 2 I realized that the rudder trim was full deflection Nose Right. We were able to bring the trim back to neutral but were unable to decipher if it was the only reason for the yaw motion or in combination with a uncommanded yaw motion from the yaw damper. At the time of the yaw motion there had been no previous trimming of the aircraft rudder trim nor aileron trim. We elected to leave the yaw damper disconnected; as a result leaving the autopilot disconnected for the duration of flight and continued to destination. After confering with dispatch we informed the Flight Attendant of the situation and made a brief announcement to the passengers for the erratic movements and that a normal landing was to be expected. During the incident we did ask ATC to remain at our current altitude and heading to troubleshoot the problem. Upon completion of the QRH and concurrence of dispatch we informed ATC that the problem had been alleviated and that we would be continuing as filed. There was no injury to passengers or crew during the incident and a normal landing was conducted. After conducting the safety conference call debrief about an hour after landing I was asked if we as a crew were able to continue. I said for the time being I believed we could continue. After getting off the phone and speaking with my First Officer and Flight Attendant we decided that regardless of when the aircraft was signed off that it would be best to not continue with the rest of our day. After having more time to go through the QRH and to think logically about what had occured I believe this was actually a rudder trim runaway. Neither I nor the First Officer had touched the trim and I believe the right turn by the autopilot in conjuction with the sudden and continuous right yaw motion led us down the path of thinking it was an uncommanded yaw motion event and subsequently performed the memory items; checklist; and QRH as such. After examining the QRH and what occured the runaway rudder trim makes the most sense but after performing the uncommanded yaw motion QRH there was no further instruction as to troubleshooting if it had been caused by a rudder trim runaway. My suggestion would be to clarify in the QRH after performing the uncommanded yaw motion checklist that the first line should read something like; 'Has the uncommanded yaw motion been caused by a rudder out of trim situation or rudder trim runaway?' If so proceed to section 10 for Rudder or Aileron Trim Runaway. I think this could have at least led us down the right path for the proper QRH given the circumstances and enabled us to re-engage the yaw damper and autopilot to continue. Given the violent yaw movement I do believe we were correct in initially suspecting an uncommanded yaw motion and performing the applicable memory items and procedures. In hindsight the rudder trim runaway was most likely the proper procedure to follow but if the uncommanded yaw motion is called for first there is nothing in the QRH to lead you towards the proper QRH; unless you ignore what was initially called for. Both QRH procedures lead to a normal landing at the destination but clarification on this would lead to a more accurate QRH being run as well as a much more clear write up when arriving at the destination.
The reporter again stated that this was a runaway rudder trim situation and that the rudder trim switch was not in use by the First Officer at the time of the runaway. No further runaways occurred during the flight and the crew was not informed by Maintenance of the actions required to return the aircraft to service.
CRJ-200 Captain reported an uncommanded yaw motion during level flight at 17;000 feet with the First Officer flying and the autopilot engaged. The Captain assumed control and performed the uncommanded yaw motion memory items and called for the QRH. During this time it was determined that the rudder was trimmed full nose right and was adjusted back to center. No further rudder anomalies occurred and the flight continued to destination.