Aircraft position roll yaw interpreted as possible engine failure in climb until PIC and first offic...

Attributes
ACN	266812
Time
Date	199403
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : yyz
State Reference	ON
Altitude	agl bound lower : 2000 agl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : yyz
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
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 : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 12000 flight time type : 1600
ASRS Report	266812
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
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	Pilot Deviation

Narrative:

Our 737-400 started to yaw left during climb, right after final flap retraction and setting climb power. My initial thought was that we'd lost an engine. A scan of the engine instruments showed no problems, so I asked the first officer to check the rudder trim indicator, because I was occupied hand flying with the trim problem. The first officer found the rudder trim position indicator moving slowly to the left, and passing 11 units. He promptly applied right trim with the trim knob until the indicator showed 0 or the centered position. No further uncommanded rudder trim movement was seen for the remainder of the flight. Callback conversation with reporter revealed the following information: reporter called back and stated that the rudder trim was not touched by any crew member prior to its 'running on its own.' this was the same type aircraft that experienced the similar incident of running on it's own but the other incident occurred after the first officer had initiated some input into the trim switch and then released it. Same air carrier but different aircraft identification. Other acn was 262802.

Original NASA ASRS Text

Title: ACFT POS ROLL YAW INTERPRETED AS POSSIBLE ENG FAILURE IN CLB UNTIL PIC AND FO REALIZE THAT THE RUDDER TRIM WAS TRIMMING TO THE L ON AN UNCOMMANDED ACTION.

Narrative: OUR 737-400 STARTED TO YAW L DURING CLB, RIGHT AFTER FINAL FLAP RETRACTION AND SETTING CLB PWR. MY INITIAL THOUGHT WAS THAT WE'D LOST AN ENG. A SCAN OF THE ENG INSTS SHOWED NO PROBS, SO I ASKED THE FO TO CHK THE RUDDER TRIM INDICATOR, BECAUSE I WAS OCCUPIED HAND FLYING WITH THE TRIM PROB. THE FO FOUND THE RUDDER TRIM POS INDICATOR MOVING SLOWLY TO THE L, AND PASSING 11 UNITS. HE PROMPTLY APPLIED RIGHT TRIM WITH THE TRIM KNOB UNTIL THE INDICATOR SHOWED 0 OR THE CTRED POS. NO FURTHER UNCOMMANDED RUDDER TRIM MOVEMENT WAS SEEN FOR THE REMAINDER OF THE FLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CALLED BACK AND STATED THAT THE RUDDER TRIM WAS NOT TOUCHED BY ANY CREW MEMBER PRIOR TO ITS 'RUNNING ON ITS OWN.' THIS WAS THE SAME TYPE ACFT THAT EXPERIENCED THE SIMILAR INCIDENT OF RUNNING ON IT'S OWN BUT THE OTHER INCIDENT OCCURRED AFTER THE FO HAD INITIATED SOME INPUT INTO THE TRIM SWITCH AND THEN RELEASED IT. SAME ACR BUT DIFFERENT ACFT ID. OTHER ACN WAS 262802.

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.

Aircraft position roll yaw interpreted as possible engine failure in climb until PIC and first officer realize that the rudder trim was trimming to the left on an uncommanded action.