An medium large transport experiences a runaway rudder trim during initial climb.

Attributes
ACN	258849
Time
Date	199312
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lax
State Reference	CA
Altitude	msl bound lower : 1000 msl bound upper : 1000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : initial
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : atp
Experience	flight time last 90 days : 173 flight time total : 9636 flight time type : 5564
ASRS Report	258849
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

I was captain of medium large transport non stop lax-bwi. First officer made the takeoff. At approximately 1000 ft MSL, while I was switching to departure control, I felt the aircraft yaw. At first I thought it was wake turbulence, then I checked the engine instruments (normal), then I checked the rudder trim. I saw the rudder trim indicator moving past 9 units right trim. I grabbed the rudder trim control knob and commanded the rudder back to neutral. The rudder responded and went back to neutral. The first officer hand flew the aircraft to FL230 where we engaged the autoplt and pulled the rudder trim control circuit breaker. No further problems were noted and we continued to bwi and wrote up the rudder trim. Our aircraft was an originator in lax. I performed a rudder trim check prior to engine start and a flight control check prior to takeoff. Both checks were normal in all respects. No rudder trim knob sticking was noted. No rudder trim inputs were made by either pilot prior to the trim running away. I do not believe this problem was caused by a sticking knob. I wonder if this is in any way related to the lga accident. I know most of us flying this aircraft would prefer the old mechanical rudder trim system that is on the medium large transport.

Original NASA ASRS Text

Title: AN MLG EXPERIENCES A RUNAWAY RUDDER TRIM DURING INITIAL CLB.

Narrative: I WAS CAPT OF MLG NON STOP LAX-BWI. FO MADE THE TKOF. AT APPROX 1000 FT MSL, WHILE I WAS SWITCHING TO DEP CTL, I FELT THE ACFT YAW. AT FIRST I THOUGHT IT WAS WAKE TURB, THEN I CHKED THE ENG INSTS (NORMAL), THEN I CHKED THE RUDDER TRIM. I SAW THE RUDDER TRIM INDICATOR MOVING PAST 9 UNITS R TRIM. I GRABBED THE RUDDER TRIM CTL KNOB AND COMMANDED THE RUDDER BACK TO NEUTRAL. THE RUDDER RESPONDED AND WENT BACK TO NEUTRAL. THE FO HAND FLEW THE ACFT TO FL230 WHERE WE ENGAGED THE AUTOPLT AND PULLED THE RUDDER TRIM CTL CIRCUIT BREAKER. NO FURTHER PROBS WERE NOTED AND WE CONTINUED TO BWI AND WROTE UP THE RUDDER TRIM. OUR ACFT WAS AN ORIGINATOR IN LAX. I PERFORMED A RUDDER TRIM CHK PRIOR TO ENG START AND A FLT CTL CHK PRIOR TO TKOF. BOTH CHKS WERE NORMAL IN ALL RESPECTS. NO RUDDER TRIM KNOB STICKING WAS NOTED. NO RUDDER TRIM INPUTS WERE MADE BY EITHER PLT PRIOR TO THE TRIM RUNNING AWAY. I DO NOT BELIEVE THIS PROB WAS CAUSED BY A STICKING KNOB. I WONDER IF THIS IS IN ANY WAY RELATED TO THE LGA ACCIDENT. I KNOW MOST OF US FLYING THIS ACFT WOULD PREFER THE OLD MECHANICAL RUDDER TRIM SYS THAT IS ON THE MLG.

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.