Narrative:

Normal flight until we were level at FL260. We felt something that we weren't sure what it was. It felt like a yaw to the right; but we were in a turn to the left. We called the flight attendants and asked them if they felt anything weird in the back. They said 'no' so we continued. About 10-12 minutes later we are in level cruise 320kts. The aircraft yawed 3/4 of the brick on the slip indicator to the right. This time the flight attendants felt it and we knew it was un-commanded yaw. We ran the immediate action item and complied with the QRH. Land at nearest suitable airport. We [advised ATC] and proceeded to a nearby airport. After getting safely on the ground talking to the crash fire rescue equipment people and deplaning; we called maintenance (mx) control. They in turn called out a local mechanic. He showed up to the plane with little or no idea of what he was there to do. He asked me if I would mind swinging the rudder full deflection from left to right using only one hydraulic system at a time. So; system 1 only on back and forth the same for 2 and then 3. I'm not sure if it's a coincidence or if he caused this problem by not referencing a task sheet so; I couldn't be sure if this was an approved procedure or not. But it caused several faults that weren't there before. Since there was no task sheet that the mechanic had for this procedure it was unclear if this was normal for this procedure or not; but now we have sscu 1 and sscu 2 fault status messages. He returns to the cockpit with 'hey guys great news the rudder travel is free and clear. You're good to go.' the mechanic performing the test of the rudder with no use of a task sheet made me a little suspicious. Now he has to deal with the sscu faults. He is on the phone with mx control. They start performing spost test. The system will not test. They have tried doing this test 4 times. Mx control tells the local mechanic to re-rack the sscu boxes in the avionics bay. They shut the plane down; re-rack and restart. The system resets and test correctly. They are all patting themselves on their backs. Nothing has been done about the yaw damper at all. To be extra vigilant after one emergency and to prevent another. I ask the local mechanic if he minds showing me the task sheet that he was given by our company. There wasn't one. Nothing. In the name of safety; I asked him to please call maintenance control back and have him fax over the task sheet for testing the yaw damper. After a while he appears with it and proceeds to run the test on the yaw damper. Finally. After all of this; I am informed that they tested okay and that they were going to defer the autopilot system. I asked why? This is a 2 axis autopilot system. That's not going to correct the problem. We still have the FCC giving signals to the yaw damper servos. After learning what they are planning to with this aircraft I called [an expert] from [a division of a manufacturing company]. I called him to confer with him about the aircraft systems. Just to confirm my thoughts. He offered to speak with mx control to tell him that the route that he was taking was not the correct. Mx control and [the expert] spoke. I then spoke with [the expert] and he said that he helped point the mx controller in the right direction. I thought that was the end of the issue. I then have the captain's phone given to me. It's mx control. He is still going to defer the autopilot against the recommendations of [the expert]. Then he explains how he had a conference call with someone in engineering; operations; and quality assurance. He feels that his work is the best resolution. At this time I have a major concern I feel like the maintenance controller has a very large educational gap of our aircraft systems and is trying to use his limited knowledge to try to strong arm us into flying an unsafe plane. I called [the expert] back he and I are on the same page he said that he would not take this plane if he were on it. I am of the same mindset. He then calls [company] and we decided to refuse the plane. [Company] called the captain and told him he would back our decision not to operate the aircraft. We did accept the 2 hour extension to operate the relief flight; but scheduling gave that flight to the fresher inbound reserve pilots. My question is why does maintenance think that deferring the autopilot (which does not disable the FCC's or yd's) would make it safe to dispatch an airplane that had already experienced a rudder hard over in flight? Shouldn't they have disabled the yd controller? The threat that mainly exposed itself was the fact that the person in maintenance control needs further education on the CRJ7/9 systems. I cannot say that this will or cannot happen again to an aircraft in our fleet. I do hope that this event has shown the weakness in some of our procedures. Maybe there can be something done about that.

Related reports:

Google
 

Original NASA ASRS Text

Title: A CRJ-700 crew experienced an uncommanded rudder input at cruise and diverted as per the QRH. A Contract Mechanic and Company Maintenance Control diagnosed the system and concluded an autopilot fault. However; this autopilot has no rudder input.

Narrative: Normal flight until we were level at FL260. We felt something that we weren't sure what it was. It felt like a yaw to the right; but we were in a turn to the left. We called the flight attendants and asked them if they felt anything weird in the back. They said 'no' so we continued. About 10-12 minutes later we are in level cruise 320kts. The aircraft yawed 3/4 of the brick on the slip indicator to the right. This time the flight attendants felt it and we knew it was un-commanded yaw. We ran the immediate action item and complied with the QRH. Land at Nearest Suitable Airport. We [advised ATC] and proceeded to a nearby airport. After getting safely on the ground talking to the CFR people and deplaning; we called maintenance (Mx) control. They in turn called out a local mechanic. He showed up to the plane with little or no idea of what he was there to do. He asked me if I would mind swinging the rudder full deflection from left to right using only one hydraulic system at a time. So; system 1 only on back and forth the same for 2 and then 3. I'm not sure if it's a coincidence or if he caused this problem by not referencing a task sheet so; I couldn't be sure if this was an approved procedure or not. But it caused several faults that weren't there before. Since there was no task sheet that the mechanic had for this procedure it was unclear if this was normal for this procedure or not; but now we have SSCU 1 and SSCU 2 fault status messages. He returns to the cockpit with 'hey guys great news the rudder travel is free and clear. You're good to go.' The mechanic performing the test of the rudder with no use of a task sheet made me a little suspicious. Now he has to deal with the SSCU faults. He is on the phone with MX control. They start performing SPOST test. The system will not test. They have tried doing this test 4 times. MX control tells the local mechanic to re-rack the SSCU boxes in the avionics bay. They shut the plane down; re-rack and restart. The system resets and test correctly. They are all patting themselves on their backs. Nothing has been done about the yaw damper at all. To be extra vigilant after one emergency and to prevent another. I ask the local mechanic if he minds showing me the task sheet that he was given by our company. There wasn't one. Nothing. In the name of safety; I asked him to please call maintenance control back and have him fax over the task sheet for testing the yaw damper. After a while he appears with it and proceeds to run the test on the yaw damper. Finally. After all of this; I am informed that they tested okay and that they were going to defer the autopilot system. I asked why? This is a 2 axis autopilot system. That's not going to correct the problem. We still have the FCC giving signals to the yaw damper servos. After learning what they are planning to with this aircraft I called [an expert] from [a division of a manufacturing company]. I called him to confer with him about the aircraft systems. Just to confirm my thoughts. He offered to speak with MX control to tell him that the route that he was taking was not the correct. MX control and [the expert] spoke. I then spoke with [the expert] and he said that he helped point the MX controller in the right direction. I thought that was the end of the issue. I then have the captain's phone given to me. It's MX control. He is still going to defer the autopilot against the recommendations of [the expert]. Then he explains how he had a conference call with someone in engineering; operations; and Quality assurance. He feels that his work is the best resolution. At this time I have a major concern I feel like the maintenance controller has a very large educational gap of our aircraft systems and is trying to use his limited knowledge to try to strong arm us into flying an unsafe plane. I called [the expert] back he and I are on the same page he said that he would not take this plane if he were on it. I am of the same mindset. He then calls [company] and we decided to refuse the plane. [Company] called the Captain and told him he would back our decision not to operate the aircraft. We did accept the 2 hour extension to operate the relief flight; but scheduling gave that flight to the fresher inbound reserve pilots. My question is why does maintenance think that deferring the autopilot (which does not disable the FCC's or YD's) would make it safe to dispatch an airplane that had already experienced a rudder hard over in flight? Shouldn't they have disabled the YD controller? The threat that mainly exposed itself was the fact that the person in maintenance control needs further education on the CRJ7/9 systems. I cannot say that this will or cannot happen again to an aircraft in our fleet. I do hope that this event has shown the weakness in some of our procedures. Maybe there can be something done about that.

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.