CRJ-200 flight crew reported experiencing a runaway rudder trim issue shortly after encountering wake turbulence. The flight continued to destination after successful troubleshooting of the rudder trim anomaly; but the flight crew stated that the QRH was missing references to perform other procedures that were related to the issue.
Synopsis
CRJ-200 flight crew reported experiencing a runaway rudder trim issue shortly after encountering wake turbulence. The flight continued to destination after successful troubleshooting of the rudder trim anomaly; but the flight crew stated that the QRH was missing references to perform other procedures that were related to the issue.
Narrative
After takeoff from ORD we encountered wake turbulence from a 737 that departed ahead of us. ATC vectored us on a northerly heading and directed us to contact an unusual Departure frequency. While I was tuning the new frequency; I felt a yawing motion; and challenged the FO (First Officer); who was flying. The FO indicated the yawing was not their doing; and we realized the rudder trim was fully deflected to the left. The FO maintained control of the aircraft and called for the Rudder Trim Runaway QRH. I searched the table of contents of the FLT CONTROLS section and at first did not locate the procedure. After reviewing the index; I found Aileron or Rudder Trim Runaway; page XX - XY. Following the QRH; I was able to re-center the rudder trim; and the runaway did not persist. In the decision tree; under Trim runaway persists: No" it says operate the trim switch with caution for the remainder of the flight. I directed the FO to not used the trim again as a precaution. The runaway did not reoccur for the rest of the flight. We coordinated with Dispatch. Given the QRH did not mention diverting; we asked for confirmation to continue to ZZZ. Dispatch informed us that there was another aircraft available at ZZZ1 and that we should divert so we could continue with a different aircraft. This is because Maintenance would not be available in ZZZ. We informed ATC; and prepared for an approach at ZZZ1. Before beginning the approach; we received another message saying that the plan to go to ZZZ1 would not work and that we should continue to ZZZ. We had an abundance of fuel; so we changed our destination again to ZZZ; and made a normal approach to landing. I do not think there is something we could have done to prevent the malfunction. To our knowledge we did not deviate from any clearances or procedures. Reflecting on the event; if the situation seemed that it was going to turn worse; I would have declared an emergency. Upon reflection; I realize there is an argument to be made that we could have declared as a precaution. At the time; we determined since the malfunction seemed momentary; that we did not require priority handling; nor was safety at stake; it was not required. Having discussed the event after the fact; we are concerned that crews may not be aware that the "Aileron or Rudder Trim" procedure exists. This makes us concerned that crews may inadvertently use the wrong procedure in the same situation. We also noticed that the "Aileron or Rudder Trim Runaway" QRH does not reference the "Uncommanded Yaw Motion" QRH although the opposite is true. "Uncommanded Yaw Motion" does reference "Aileron or Rudder Trim Runaway.""
Second reporter narrative
During initial climb after departing ORD 9C/FF on runway heading; was given a left turn to heading 360. During this turn; the Captain; pilot monitoring; and I observed the PFD (Primary Flight Display) inclinometer; the brick;" move toward the right. When the Captain prompted me; I responded that this yawing occurred without a corresponding rudder pedal or thrust lever input by me. Glancing at the rudder trim gauge; we noted a full left rudder trim indication. I called for QRH Rudder Trim Runaway procedure. The QRH steps were followed and the rudder trim knob was rotated by the Captain to recenter the rudder trim. Because the trim runaway condition did not persist; the QRH indicated that the trim switch should be used with caution for the remainder of the flight. We agreed that we should notify Dispatch and did so. Dispatch directed a change to our destination for operational reasons and ATC; Flight Attendant and passengers were subsequently notified. Delay vectors were requested to create time. Destination weather was obtained; and appropriate briefings; checklists and arrival procedures were completed. Dispatch subsequently notified us that this destination change would no longer be necessary and we should proceed to original destination. Once again; ATC; Flight Attendant and passengers were notified. Once again delay vectors were requested; destination weather was obtained; and appropriate briefings; checklists and arrival procedures were completed. A normal approach and landing were completed without event.At present; the QRH for Uncommanded Yaw presents a note: "See Aileron or Rudder Trim Runaway in Flt Controls page XX - XY if problem is actually a Runaway Trim." There is no similar cross-reference to Uncommanded Yaw in the QRH procedure for Aileron or Rudder Trim Runaway."
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.