Narrative:

On july/fri/2004 on a flight from ZZZ to ZZZ1, the first officer was flying. After acceleration altitude, the first officer stated that he had an aileron trim runaway. After trying to re-center the trim with negative results, the circuit breakers were pulled per the company flight manual. The trim was in a full left configuration. An emergency was declared and the flight returned to ZZZ uneventfully. Callback conversation with reporter revealed the following information: the captain declared an emergency and requested crash fire rescue equipment for the landing. When this happens in the simulator, the crew is taught to pull the trim circuit breaker, and then actuate the trim switches in the opposite direction. This relieves the force on the ailerons. The crew followed the checklist, and pulled the circuit breaker, but was still not able to relieve the aileron pressure. Maintenance replaced a trim actuator.

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Original NASA ASRS Text

Title: DHC8 CREW HAS AN AILERON TRIM RUNAWAY. DECLARED AN EMER AND RETURNED TO DEP ARPT.

Narrative: ON JULY/FRI/2004 ON A FLT FROM ZZZ TO ZZZ1, THE FO WAS FLYING. AFTER ACCELERATION ALT, THE FO STATED THAT HE HAD AN AILERON TRIM RUNAWAY. AFTER TRYING TO RE-CENTER THE TRIM WITH NEGATIVE RESULTS, THE CIRCUIT BREAKERS WERE PULLED PER THE COMPANY FLT MANUAL. THE TRIM WAS IN A FULL L CONFIGURATION. AN EMER WAS DECLARED AND THE FLT RETURNED TO ZZZ UNEVENTFULLY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT DECLARED AN EMER AND REQUESTED CFR FOR THE LNDG. WHEN THIS HAPPENS IN THE SIMULATOR, THE CREW IS TAUGHT TO PULL THE TRIM CIRCUIT BREAKER, AND THEN ACTUATE THE TRIM SWITCHES IN THE OPPOSITE DIRECTION. THIS RELIEVES THE FORCE ON THE AILERONS. THE CREW FOLLOWED THE CHECKLIST, AND PULLED THE CIRCUIT BREAKER, BUT WAS STILL NOT ABLE TO RELIEVE THE AILERON PRESSURE. MAINT REPLACED A TRIM ACTUATOR.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.