A large amount of required rudder trim lead a B-767-300 flight crew to investigate their flight controls. Doing so alerted them to the inboard ailerons both being deflected up a significant amount with the yoke in neutral. An emergency was declared and the flight diverted to a nearby airport for maintenance attention.

Narrative

During cockpit setup; noted rudder trim was 3-4 units to the left before zeroing it out. During the climbout; the First Officer advised that significant rudder trim to the left was in fact needed. Upon reaching cruise altitude; we performed the aircraft trimming additional procedure to determine if the amount of rudder trim used (3-4 units) would require a write up; and surprisingly it was within acceptable limits. Fuel balance was good. Called up the status page on the lower EICAS and looked at the flight control matrix; which showed that both inboard ailerons were partially up; with the right inboard aileron up 1/4 to 1/3 of its travel. Performed very small course change right and left; observed only the left inboard aileron position indicator moved. Had the First Officer go into the cabin and verify actual right inboard aileron position. He said it did not move while turning and was obviously displaced out of neutral towards the up position. At that point sent ACARS message to Dispatch to call us and include airframe Maintenance in the discussion. Maintenance concurred that there were no further actions we could take; and we collectively agreed a diversion was the best course of action for safety and for passenger accommodations. The flight attendants and passengers were briefed; an emergency was declared; and the divert was initiated. I then took control of the aircraft for the divert and landing. As we descended; we set up for a long final and configured the aircraft per the Controllability Checklist in the maneuvers section of the AFM (Aircraft Flight Manual). The aircraft handled well throughout the configuration changes; though 4-5 units of trim were required. When selecting 30 flaps; we noted a light to moderated airframe buffet that had not been present at phase of the flight. [We] repositioned the flaps to 25; and set Vref plus 20 KTS for our approach speed. Approach and landing were uneventful. Prior to exiting the runway; we noted that the inboard right aileron had now returned to neutral and was symmetrical with the left inboard aileron.