Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Inflight Event / Encounter Other / Unknown
Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Declared Emergency
Aircraft
CRJ-200 aircraft departed with passengers and three crew members. Flight was 90 miles north of [our next fix] and was flying direct to [it] per ATC. The aircraft was on autopilot and was climbing at 290 KTS IAS through FL250 up to FL280. The flight conditions at the time were VMC and no turbulence. As the aircraft climbed to final cruise altitude; the crew observed the aircraft slightly yaw in both directions; it felt like a 'kick'. The aircraft then self-corrected back to wings level. This occurred two more times within a few minutes of each other. The crew verified that the hydraulics were all in the 'Normal' operating range. The Captain instructed the Flight Attendant to suspend cabin service and return to her seat. The seat belt sign was still on at the time. The aircraft was now at FL280. The rudder pedals were 'guarded' by both crew members as a precaution while they monitored the aircraft and the Flight Control Page for any abnormalities. Moments later the aircraft once again began a yawing moment in both directions. This time the yawing was more pronounced and the aircraft entered a 'Dutch Roll'. The Captain immediately took control of the aircraft; disconnected the autopilot and flight director and corrected the aircraft attitude. The Captain felt intermittent oscillation of 'bumps' in the rudder pedals and needed to apply control inputs to the rudder pedals to counteract the rudder pedals from yawing the aircraft. The QRH for Uncommanded Yawing Emergency Procedure was completed. The aircraft diverted to [a nearby airport]; conducted an ILS approach and landed. During the descent to landing; the Captain felt intermittent oscillations in the rudder pedals followed by slight yawing in both directions but was manageable. The aircraft landed at 45;400 LBS and taxied to the gate without incident.
Reporter stated rudder movement continued to be indicated on their EICAS Flight Control Page throughout the flight and was also felt in the aircraft's movement.  Initially; he and the First Officer (F/O) were not sure if they were being hit by strong crosswinds during their climb. But when the 'Dutch Roll' occurred; he immediately disconnected the Auto-Pilot; Flight Director and Yaw Damper to take control of the upset and followed the remainder of their QRH for 'Uncommanded Yawing Emergency Procedures;' those procedures also instructs pilots to place both feet on the rudder pedals.Reporter stated a stronger 'kick' in the sudden yaw oscillations were noticed along with wings dropping after the Yaw Damper was turned 'Off' and continued until they landed. He has experienced unusual upsets in the past and trained in simulators for certain upsets; but this event included a continued intermittent and pulsating yawing.  Both rudder pedals were moving with the yaw oscillations and he had to apply greater force to counter the uncommanded yaw input.  He remembered the two previous B737 aircraft that had crashed due to uncommanded rudder movements and felt they should get their CRJ-200 aircraft on the ground as quickly as possible. He continued to adjust flap settings on approach and landed with Flaps-45 without any problems.
A Captain reports experiencing uncommanded yawing oscillations and rudder pedal movement in a CRJ-200 aircraft during climb to final cruise altitude. When the CRJ entered a 'Dutch Roll'; the pilot disconnected the autopilot and flight director to correct the aircraft attitude. Flight diverted. During descent; oscillations continued to be felt in pedals with yaw in both directions.