A300
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 60; Flight Crew Total 17000; Flight Crew Type 6000
Aircraft Equipment Problem Critical
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
On takeoff I had to add right rudder in to keep the aircraft straight right from lift off. I looked at the rudder trim and saw it was at 3.8 units. My First Officer was busy talking to departure and I believe we were given a climb to 12;000 FT. I had my First Officer look at the rudder trim and he too noticed it was adding left trim in as well; we both tried to zero the trim out; but it kept adding trim into the rudder. I called for him to select the number one autopilot. With the rudder trim being added; the autopilot could not handle the inputs and was automatically clicked off; tried the number two autopilot with the same action. We were now climbing through 10;000 FT and I asked to level off and return due to the problem. I also asked the jump seat Captain to come up and help with the rudder trim and as a third pair of eyes; because I had to hand fly the aircraft and my First Officer was very busy talking with company and ATC. I had to use right rudder all the way to landing to keep the aircraft straight. We landed uneventfully; and taxiing in the rudder trim was still adding left input; as I remember the rudder trim had 3.8 units in by the time we made the short taxi into the gate. We also went to the QRH for the runaway rudder trim checklist.
After takeoff the Captain noticed that he had to input rudder to eliminate aircraft yaw. He asked me to confirm that the Rudder Trim Window indicated approximately 3.5 units of trim. I did so; and then he manually trimmed the rudder back toward zero. We both noticed that the Rudder Trim Window showed a slight fluctuation in the units of trim. As we continued to analyze the trim; during climb-out with clean configuration and Autopilot 1 actuated; aircraft rudder trim fluctuations and self-actuation's became more noticeable. Initially; trim seemed to fluctuate +/- .4 to .5. The Rudder Trim indicator window on the center pedestal reflected this rudder movement; in spite of crew inputs to the control knob to counter the rapid trim fluctuations. At approximately 8;000 FT MSL; a more significant yaw was experienced and the autopilot kicked off. The Captain immediately re-assumed control; and aircraft stability was not in question. Autopilot 2 was attempted; and did in fact hold for several seconds; and then another subsequent yaw caused that autopilot to kick off as well. When the Captain again began hand-flying; he commented that he had to maintain rudder force to counteract the out-of-trim rudder. I again zeroed-out the rudder trim manually; but at this point the indicator was fluctuating +/- .6 or .7 on its own. The Captain quickly made the decision to make a precautionary return. I coordinated with ATC and sent a quick divert message to the Company. He also called our Company jumpseater to come forward and assume responsibility for monitoring the rudder trim and manually returning it to zero if any uncommanded actuations occurred. The Jumpseater did so; and noted that the rudder trim indicator continued to fluctuate on its own. We also referenced the QRH for any procedural guidance; but the Rudder Trim Checklist was not helpful because the autopilot would not stay engaged and the Rudder Trim would not remain at or close to zero unless constantly monitored and corrected. During the short vectors; I was also able to communicate with Company Flight Control to advise them of our situation and plan. They concurred and the rest of the flight was uneventful.
A300 flight crew experiences uncommanded rudder trim inputs during takeoff and climb. Neither autopilot will remain engaged and the crew elects to return to the departure airport.