Date: 201409
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: During climb at approximately 11;000 ft; I noticed a single; very slight yaw; accompanied by Yaw Damper 1 disconnecting and its associated status message.  The yaw could have very well been chop; a slight wake or simply climbing into a different wind layer.  Additionally; yaw dampers do accidently disconnect from time to time.  I didn't think anything of this occurrence and we reengaged Yaw Damper 1; continued the flight and said we would keep an eye on it.  Once we leveled at our cruising altitude of 29;000 ft for a few minutes; we experienced the same yawing motion as before; but more pronounced.  It was also accompanied by Yaw Damper 1 simultaneously disconnecting at the same time as the yawing motion.  This time the yaw motion became intermittent and eventually constant.  The most accurate way I can describe the motions were short 'chop' or 'turbulence'-like motions; but about the aircraft's vertical axis in the lateral plane; accompanied by a slower overall yawing motion.  All yaw movements always occurred to the left.  The first officer was flying pilot during this flight.  I told him I would like him to maintain control of the airplane and we were going to consult the QRH procedure for 'Uncommanded Yaw Motion'; but before we did; I wanted to guard the yoke while we disconnected the autopilot.  I wanted to see how the aircraft was truly behaving without any motions or movement being masked by the autopilot.  I put my hands up next to the yoke and the autopilot was disconnected by the crew.  The aircraft behaved the same whether the autopilot was on or off with the same choppy yawing motions and swings.  The first officer took turns at the controls with the autopilot off so that we could both get a feel for the problem first hand.  Control of the aircraft and radios was given back to the First Officer and I ran the QRH procedure for 'Uncommanded Yaw Motion'.  Upon completing the QRH procedure; the First Officer and I briefly discussed where to divert the flight.  We had originally considered continuing north toward ZZZ1 where the passengers could be more easily reaccommodated.  However; the longer we flew the aircraft once the yawing motions were encountered; the stronger and more pronounced they became.  This led me to contemplate how much worse the yawing motions might become and whether this would lead to the aircraft becoming  uncontrollable if we continued to fly it. We made the decision to land at the nearest Air Carrier X's airport that we were familiar with.  ZZZ2 was only 40-50 miles east of us and we made the decision to divert there. QRH procedure for 'Uncommanded Yaw Motion' was completed and the flight was diverted to the nearest suitable airport as instructed by the QRH.  The Flight Attendant was briefed.  A passenger announcement and explanation was made.  We sent a brief ACARS text message to dispatch to advise them the flight was diverting to ZZZ2 for Uncommanded Yaw Motion.  The flight was flown by hand for the entire decent and approach to ZZZ2.  No ATC assistance was requested.  We made a normal landing and passengers were not asked to brace for landing.  No fire trucks or emergency equipment were summoned at the ZZZ2 airport.  This is the fourth time this same CRJ-200 aircraft has been written up for 'Uncommanded Yaw Motion' in September and October.  I know our mechanics do a good job and do their best to diagnose problems with our aircraft.  However; I don't believe the true cause of this problem has been properly diagnosed yet.  I think we're still in the phase where we're just 'throwing parts at the aircraft' until the problem does not reoccur.  Admittedly; I am not a mechanic and I have no first hand knowledge of the difficulty of these mechanical diagnoses.  However; as a flight crew member; it is frustrating to see an aircraft returned to service four times with the same problem; especially a problem where the potential controllability of the aircraft is brought into question.

Callback: Reporter stated he disconnected the Autopilot at FL290 and hand flew the aircraft all the way down to landing. Yaw Damper-2 (YD-2) was engaged the entire time. He does not remember if the rudder pedals followed the uncommanded yaws. They ferried the CRJ-200 to their Maintenance Base the next morning after Maintenance replaced both Flight Control Computers (FCCs); yaw damper issues did not recur at that time.

Second narrative: Captain and myself as First Officer; operated a Canadair Regional Jet (CRJ200) from ZZZ to ZZZ1. As we climbed through 11;000 feet; we encountered a slight left yawing motion of the aircraft. The motion carried a disengagement of Yaw Damper 1 (YD-1) and it's accompanied status message. Yaw Dampers have been known to disengage from time to time; Captain reengaged it and no other indications or malfunctions persisted until reaching a cruising altitude of 29;000 feet. After about five minutes at cruise YD-1 disengaged for a second time. In a brief attempt to troubleshoot the error; Captain reset the autopilot prior to reengaging YD-1. However; the result was unsuccessful. Captain then referenced the Quick Reference Handbook (QRH) and I; as First Officer assumed the radios and manual control of the aircraft.The initial tendencies of the left yawing motion were subtle; but the oscillations were growing and required more control input to keep the aircraft in equilibrium. As the oscillations grew; the phenomena known as Dutch Roll began to set in and the ability to control the aircraft became very apparent. Upon completion of the QRH; Captain assumed the pilot flying duties and I became the pilot monitoring.  It was determined that an event occurred due to YD-1 disconnection with it's accompanied status message and Left jerking-like yaw motions about the vertical axis in the lateral plane; with a subsequent uncommanded yaw motion. YD-1 was reengaged two to three times during the flight and subsequently refused to stay on.  Additionally; manual control of the aircraft became more difficult as the aircraft would not stay in equilibrium due to YD-1 disconnect. The oscillations of the aircraft were yaw and roll motions (Dutch Roll) which became larger in force as the flight continued at FL290.The event occurred as a result of a YD-1 failure. Historically the maintenance records indicated a known problem with YD-1 and uncommanded yaw. Captain and I agreed that the oscillations and onset of Dutch Roll were making the aircraft significantly more difficult to control. We analyzed the situation and considered our options of continuing to the destination or potentially ZZZ1 where passengers would have a plethora of flights to get them to their final destination. However; with the aircraft continuing to become more unstable and difficult to control and at the direction of the QRH; we decided that it was in the interest of safety to follow the QRH direction to divert to the nearest suitable airport; ZZZ2.Captain landed the aircraft with no further incident or accident resulting from the emergency. Once the aircraft was deplaned; the crew radioed for and waited onboard for Maintenance Control (MC). A number of checklists were accomplished for diagnostic purposes. MC was able to generate a numerical code from the aircraft and it was determined that the two flight computers were unable to successfully communicate with one another. Additionally; upon further investigation; the maintenance records of indicated that there had been a number of previous problems with the yaw damper system.Given the history (Maintenance Records) of that CRJ-200 aircraft; it seems logical to believe that the deep seated problem hasn't been identified. The aircraft is on a 'fly; fix; fly;' system (I.E. throwing parts at the plane). Which only fixes immediate problems and lowers risk to an acceptable level; rather than eliminating a hazard all together. I do deeply believe that we have a great maintenance crew and my knowledge of maintenance issues are limited. Perhaps we could work with Bombardier to come up with a better resolution of this issue.   Uncommanded Yaw.

Second callback: Reporter stated he only used the ailerons while the Captain was checking their QRH procedures because they were not sure what inputs might make the situation worse. Their Chief Pilot later told both of them they should have kept flying to their original destination.

Synopsis: A Captain and First Officer report about uncommanded left yaw motions similar to choppy; jerk like movements while climbing from 11;000 feet to 29;000 feet on a CRJ-200 aircraft. Yaw Damper-1 had disconnected twice while uncommanded yaw oscillations and roll motions (Dutch Roll) continued with Autopilot 'On' or 'Off'. Aircraft control became increasingly difficult; flight diverted.