DHC8 crew has an aileron trim runaway. Declared an emergency and returned to departure airport.

Attributes
ACN	624821
Time
Date	200407
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : zzzz.vor
State Reference	US
Altitude	msl single value : 7000
Environment
Flight Conditions	IMC
Weather Elements	Rain
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : zzz.tracon
Operator	common carrier : air carrier
Make Model Name	Dash 8 Series Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine pilot : private pilot : instrument
Experience	flight time last 90 days : 175 flight time total : 4500 flight time type : 500
ASRS Report	624821
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist controller : issued new clearance flight crew : declared emergency flight crew : landed in emergency condition flight crew : diverted to another airport
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

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.

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.