Flight Crew Air Transport Pilot (ATP)
Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Aircraft
[We] departed normally with the First Officer flying (a well-qualified and professional pilot that I have flown with on many occasions). In the climb it was observed by him that the slip/skid indicator showed that the aircraft required some right rudder. He barely set foot on the right rudder pedal and the aircraft yawed violently to the right. I asked him what he did and he stated that he hardly touched the pedal and the aircraft did that. He used the rudder trim to set the aircraft straight and engaged Number 2 autopilot. We noted and discussed the fact that the trim was set to 2.5 nose right. I commented that this was not right as I had not recalled ever seeing an Airbus trimmed like that before. As we talked further; the auto trim continued to trim the rudder to 2.9-3.1 nose right. Within the next 3 to 5 minutes the aircraft yawed to the right and then left hard enough that one of the flight attendants said that it sent her from one side of the plane to the other at the aft section of the plane. At this point I disconnected the autopilot and turned off all automation. We told ATC that we needed to return as we had an issue with the rudder. We declared an emergency and were given a clearance directly to the airport. During the time back to the airport we experienced several more uncommanded rudder inputs. Aircraft required about half scale deflection of the rudder to the left to fly it back. Light pressure release or any application of rudder trim caused huge variations in the yaw of the aircraft. We elected not to do anything with the rudder or trim and to leave things status quo. Aircraft flew normally other than all the left rudder required. Landed without incident and taxied to the gate.
The reporter states that there were no ECAM messages or any fault lights during the entire flight and that maintenance could not initially find any faults. Maintenance was eventually able to reproduce the rudder kick on the ground and trace the fault to one of the FAC's; which was replaced.
After takeoff; during initial climbout; I noticed the slip indicator was off. I started to apply a small amount of rudder correction. The aircraft reacted as if I had stomped on the rudder. Then I was able to push on the rudder again to correct the skid and started to trim the pressure off. At about 2.5 trim right; I engaged the autopilot. The Captain and I discussed what happened as the airplane continued to trim itself to about 2.9-3.1. Then the airplane had another uncontrolled rudder input while on autopilot. The Captain took control of the airplane and disconnected the autopilot. I declared an emergency and we returned without incident.
A319 flight crew experiences an out of trim situation during initial climb and when the First Officer applies slight rudder pressure the aircraft yaws dramatically. Trim is used to center the brick and the autopilot engaged; resulting in about three units of nose right rudder trim. Another sharp yaw event is produced with the autopilot engaged and the crew elects to return to the departure airport.