Aircraft electric rudder trim momentarily failed to shut off after activation by flight crew.

Attributes
ACN	143657
Time
Date	199003
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mmex
State Reference	FO
Altitude	msl bound lower : 24000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : mmex
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	143657
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

On departure from mexico city on a scheduled flight to san francisco the copilot was manually flying the aircraft. Climbing thru FL240 he added some right rudder trim. He then felt that he had to put in aileron to maintain wings level. Then he said, 'hey, we have a runaway rudder trim.' I looked down at the console and noted the rudder trim indicator just moving past 5 degree right rudder. The copilot then moved the trim knob to the left and the right trim stopped and the rudder returned to his desired trim position.

Original NASA ASRS Text

Title: ACFT ELECTRIC RUDDER TRIM MOMENTARILY FAILED TO SHUT OFF AFTER ACTIVATION BY FLT CREW.

Narrative: ON DEP FROM MEXICO CITY ON A SCHEDULED FLT TO SAN FRANCISCO THE COPLT WAS MANUALLY FLYING THE ACFT. CLIMBING THRU FL240 HE ADDED SOME RIGHT RUDDER TRIM. HE THEN FELT THAT HE HAD TO PUT IN AILERON TO MAINTAIN WINGS LEVEL. THEN HE SAID, 'HEY, WE HAVE A RUNAWAY RUDDER TRIM.' I LOOKED DOWN AT THE CONSOLE AND NOTED THE RUDDER TRIM INDICATOR JUST MOVING PAST 5 DEG RIGHT RUDDER. THE COPLT THEN MOVED THE TRIM KNOB TO THE LEFT AND THE RIGHT TRIM STOPPED AND THE RUDDER RETURNED TO HIS DESIRED TRIM POSITION.

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.