Cessna Citation Sovereign (C680)
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem
Aircraft
During cruise at FL410 I noticed the pitch trim indicator was moving uncommanded. Normal cruise is around 0.3 units nose up. The trim was indicating about 2.5 units nose up and increasing. I notified my partner and he put both hands on the yoke and was prepared for the aircraft to rapidly pitch up. I was expecting the autopilot to disengage; it never did. The trim indication stopped at 8.0 units nose up. My partner disconnected the autopilot and said the airplane was trimmed and flying normally. He bumped the pitch trim switch and the indication immediately went back to a normal cruise setting of 0.3 units nose up. He then re-engaged the autopilot. We were both monitoring the trim indication and after about five to ten minutes the situation repeated. This time the trim indication stopped at 8.3 units nose up. My partner once again disengaged the auto pilot; bumped the pitch trim switch and the pitch trim indicator returned to a normal cruise value. At no time during these events did the clacker sound as would happen if the stab was commanded to move with the autopilot engaged. We reviewed the checklist and discussed what we would do if the attitude of the aircraft were too changed uncommanded. We contacted Maintenance via flight phone and were transferred to the ACP. We all were in agreement to continue to the destination and monitor the situation. The remainder of the flight was uneventful. Looking back; it is my opinion that the stab never moved uncommanded. I believe this was just a faulty stab trim display indication. I believe that by verifying what the airplane was doing before rushing into memory items and/or checklist items we were able to maintain positive control of the aircraft. I can see how it would be easy to assume something was happening and without verifying make the situation worse.
CE-680 First Officer reported noticing pitch trim indicator reading abnormally high in cruise flight. When autopilot was disengaged it was apparent the indicator was wrong and the trim was not actually moving out of the normal range.