Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 8352
Aircraft Equipment Problem Less Severe
Flight Crew Diverted
Aircraft
Captain flying; First Officer monitoring. At 39;000 FT with autopilot A coupled; we felt (can be described as) a kick. It was enough that we both took notice. It happened a second and then a third time. We then elected to kick off the autopilot and feel what was happening. We both agreed that something was not right and that the aircraft controls were doing something that was not normal for our phase of flight. We made adjustments to the rudder trim while getting the QRH out. Rudder trim seemed to be having an unusual effect; meaning a little trim was pushing and pulling the aileron trim pointer on the control wheel in large movements (not the usual amount). At this time we felt there [was] something wrong with our control system and elected to return to GUM; as we were heading into an ETOPS flight with no suitable airports in the area. We [notified Flight Service] on HF; as we were unsure of the actual problem so we unable to predict whether it would get worse or not. Once on a direct track to Guam we notified Dispatch; Maintenance; and went through [emergency checklist] with flight attendants. We landed in GUM without incident.
Air Carrier flight crew diverted to Guam due to flight control malfunction.