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.

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Original NASA ASRS Text

Title: 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.

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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.