Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Human Factors; Procedure
How should a flight crew respond when their aircraft suddenly exhibits apparent flight control malfunctions which don't have a corresponding QRH procedure? Here is how we handled the situation when it happened to us: The flight crew consisted of [our] Captain; Flight Attendant and I; as First Officer. During that flight I was pilot flying; and while enroute at FL300 with autopilot engaged; the aircraft suddenly and abruptly yawed first in one direction; then the other; followed by EICAS displaying a Yaw Damper-1 (YD-1) INOP status message. We attempted to reset YD-1; but within moments YD-1 disengaged itself again; with another significant lateral movement of the aircraft and corresponding deviation of the EFIS 'brick'. Moments prior to YD-1 disengaging a mechanical 'shudder' was felt in both rudder pedals.There is no specific QRH procedure for operating with one Yaw Damper INOP; so we referenced QRH 'YAW DAMPER Caution Message' in case we lost the other Yaw Damper; kept YD-1 off; continued to destination and landed there. Contract Maintenance came out; and after troubleshooting it was decided that the aircraft should be ferried under Special Flight Permit with YD-1 disengaged. As YD-1 was to remain disengaged; we briefed the departure at the gate to include possibly having to reference QRH in the event that YD-2 also went offline. We took off with the Captain flying and me performing pilot not flying duties. Ride conditions were smooth and everything appeared normal until approximately 16;000 FT in the climb; at which time a sudden; abrupt lateral movement was felt. It seemed to be the same symptom as we had experienced on our earlier flight.We verified that YD-1 was still disengaged and YD-2 remained engaged; nevertheless after a few moments we felt another sharp lateral movement. Thinking that we might now have a problem with YD-2; and with no specific QRH procedure available; we reasoned that disconnecting YD-2 might resolve the issue. We disconnected YD-2; which also resulted in disconnection of the autopilot. At first it seemed like the issue was resolved; but after approximately 30-45 seconds the aircraft again abruptly deviated laterally. For a time; the aircraft remained in a skid with the 'brick' displaced to the left; showing that left rudder trim was needed. The Captain applied left rudder trim; but the 'brick' unexpectedly moved even further left. The trim was then neutralized; but while EICAS indicated that the rudder trim had returned to neutral; the aircraft continued to skid with the 'brick' displaced to the left. Additional abrupt deviations were felt in both directions for the remainder of the flight with increasing frequency and variable extent.I estimate that on average we experienced these excursions at intervals ranging from approximately once every 45 seconds to one minute; but with occasional 'bursts' of multiple excursions in the space of 5-10 seconds. The frequency and severity seemed random; both before and after YD-2 was disengaged. I must stress that these events were not related to turbulence; nor were they the result of any control input by the flight crew. I have flown both the CRJ-200 and 900 series for several years under a wide variety of conditions; however the only time I have encountered similar symptoms was during my initial simulator training while the SIM instructor was demonstrating flight with both Yaw Dampers disengaged and my SIM partner kicked the rudder pedals sharply (as directed by the SIM instructor).The excursions we experienced were spontaneous and on occasion quite violent; sometimes resulting in approximately 15-degrees of heading change in one second with no apparent change in track. We appeared to have a Primary Flight Control malfunction with an unknown cause producing unpredictable effects; and were concerned that the excursions might worsen and perhaps eventually become unrecoverable. We decided it would be prudent to land the aircraft as soon as practicable. The next airport on our route was directly ahead of us about 15 minutes flying time; we declared an Emergency and initially requested clearance there; and began a descent to 10;000 FT. We were cleared as requested; but while descending we realized another airport was considerably closer (approximately 20 NM away); and also had a long runway (12;600 FT). We decided to go there instead; and were re-cleared direct to that airport; then handed off to Approach. We requested weather; which was reported as wind calm; BKN027; 10SM; and we were told to expect an ILS approach. We configured the FMS and NAV radios; briefed the Flight Attendant; and performed the Descent and Approach Checklists. The aircraft continued to exhibit erratic lateral controllability; but the Captain was able to hand-fly to the final approach course and join the localizer inbound. We decided to land at Flaps 20; because we believed we might retain better controllability with a faster approach speed and the resultant higher airflow and a flatter touchdown profile. We also referenced QRH because with both Yaw Dampers disengaged we had the YAW DAMPER Caution message displayed; and this procedure directs a landing at Flaps 20. We completed the approach and landed under control; rolled out and cleared the runway; and were directed by Ground crew to a hardstand. Knowing that maintaining [electrical] power was essential to preserving any fault codes; we kept the APU running for an hour or more while waiting for a Ground Power Unit to become available. After establishing Ground Power we handed the airplane over to the ground personnel; having explained to them that it was imperative that the [electrical] power remain on until Maintenance arrived.
We were to be operating flight as a Maintenance Ferry Flight under Special Flight Permit. This was done as a result of experiencing uncommanded lateral movement [yaw] followed by Yaw Damper-1 (YD-1) failure on our inbound flight. Hence the flight was to be operated with only Yaw Damper-2 (YD-2) engaged and available. Minimum flight crew of three was on board; myself as PIC; First Officer and a Flight Attendant. After receiving proper documentation from a contract Maintenance Technician; plus required briefings from Maintenance Control and Duty Chief Pilot with regards to the Special Flight Permit; we pushed back and taxied for departure. I was the pilot flying; Climbing through 15;000 FT; autopilot was engaged; Speed Mode 290 KTS and FMS in the active FMA window and only YD-2 available and engaged. Reaching 16;000 FT; the aircraft made sharp; lateral uncommanded movements; resulting in a heading change of about 10-15 degrees on the either side of the course. About 30-seconds later; additional uncommanded movement was experienced but with a bit more of a sharp and choppy lateral displacement. On the earlier flight; we had experienced similar uncommanded movement and it had resulted in YD-1 failure. Since on the earlier flight situation; the uncommanded movement ceased after the YD-1 had failed; hence based on this earlier experience; it seemed as if the YD-2 might be suffering a similar malfunction. For the sake of logical; rational reasoning and after experiencing some more uncommanded inputs; the YD-2 was disengaged; which in turn disengaged the autopilot. Thereafter; the whole flight was flown manually. The uncommanded lateral movements kept reoccurring approximately every 30 to 60 seconds. There is no QRH procedure available to remedy this malfunction; but we utilized the QRH 'YAW DAMPER MSG' as a reference. (NOTE: The intensity and frequency of the uncommanded lateral movement was more or less similar; before and after the YD-2 was disengaged.) At this point we had no idea what was causing this uncommanded lateral movement; and whether or not it might worsen; and perhaps cause a complete loss of control. An Emergency condition was declared; 'Primary Flight Control malfunction- Rudder control'. We selected a diversionary airport; about 100 NM to the north. We chose not to turn back due to thunderstorms approaching the airfield and to avoid turning as much as possible. While the FO was preparing for arrival; the uncommanded lateral movements started occurring much more frequently and with each new one the intensity seemed to be escalating. (Note: I would like to point out that at this time we were straight and wings level; descending to 10;000 FT. No turns were performed and the ride conditions were smooth; hence no lateral movements were commanded by us.) As the unknown was getting worse we decided to divert to a closer airport. It has a 12;600 FT long runway; is a very familiar airport and has scheduled mainline service. ATC was notified of the change.Since we had no idea if this aircraft will land properly; as it is very likely that during touchdown and flare; an uncommanded movement can cause an unrecoverable situation; therefore CFR was requested to be available by the Runway. Company was notified via ACARS; the Flight Attendant was briefed; and she secured the cabin and herself. (Another fact to be noted is that while slowing to 250 KTS; the 'Turn/ Slip indicator' ('Brick') was displaced to the left; on applying left rudder trim the 'Brick' further displaced to the left. In response; I neutralized the rudder trim and manually controlled the slip/skid condition by attempting to center the 'Brick' with smooth rudder inputs).
A Captain and First Officer report experiencing sudden; sharp; uncommanded lateral rudder inputs while flying a CRJ-200 aircraft during a revenue and ferry flight. Uncommanded lateral movements kept recurring every 30 to 60 seconds even with yaw dampers-1 and -2 and autopilot disengaged. No QRH procedure available to remedy malfunction. Emergency landing was declared.