As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX FLIGHT 9850. RT AILERON TRIM SWITCH STUCK WHEN APPLYING TRIM. TRIM RAN AWAY TO THE RT. WAS ABLE TO NEUTRALIZE TRIM BY APPLYING LT AILERON TRIM FIRMLY. THE SWITCH APPEARED TO BE STUCK. MX R&R THE AILERON/RUDDER TRIM CONTROL-PANEL PER Q400AMM TASKS 27-13-16-000-801 AND 27-13-16-400-801. OPS TEST GOOD. RETURNED TO SERVICE.