Narrative:

We picked up act XXXX in oakland. Aircraft was unpowered and we pwred up with ground power 90 mins before departure. Performed originating checks 30 mins prior to departure and found rudder trim to be centered. 5 mins before departure as I adjusted my seat I noticed the rudder pedals were displaced. We found the rudder trim to be fully deflected to the right. We believe the rudder trim actuated by itself as the rudder trim switch was not touched the entire time. The power source was not changed, this sounds very similar to lga as it was also raining in oak. I believe now that the rudder trim can runaway at any time and that a trim-in-motion horn and a takeoff trim position warning are mandatory. A switch guard will not solve the problem. Thanks for the fil explaining how to detect trim displacement. Callback conversation with reporter revealed the following information. Reporter is certain that rudder trim input was not cockpit action induced. He offers the theory that the prevailing WX conditions primarily rain may have affected the trim switches although he admits that it seems unlikely. The captain is certain that the trim and rudder position was centered when checked during cockpit setup and that the movement took place thereafter. Reporter states that he recently flew a brand new example of this aircraft and noted that it had a modified trim activation system so the problem has been acted on to some extent by the aircraft mfr.

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Original NASA ASRS Text

Title: FLC DISCOVERS FULL RUDDER TRIM INPUT ON ADVTECH MLG DURING PREFLT.

Narrative: WE PICKED UP ACT XXXX IN OAKLAND. ACFT WAS UNPOWERED AND WE PWRED UP WITH GND PWR 90 MINS BEFORE DEP. PERFORMED ORIGINATING CHKS 30 MINS PRIOR TO DEP AND FOUND RUDDER TRIM TO BE CENTERED. 5 MINS BEFORE DEP AS I ADJUSTED MY SEAT I NOTICED THE RUDDER PEDALS WERE DISPLACED. WE FOUND THE RUDDER TRIM TO BE FULLY DEFLECTED TO THE R. WE BELIEVE THE RUDDER TRIM ACTUATED BY ITSELF AS THE RUDDER TRIM SWITCH WAS NOT TOUCHED THE ENTIRE TIME. THE PWR SOURCE WAS NOT CHANGED, THIS SOUNDS VERY SIMILAR TO LGA AS IT WAS ALSO RAINING IN OAK. I BELIEVE NOW THAT THE RUDDER TRIM CAN RUNAWAY AT ANY TIME AND THAT A TRIM-IN-MOTION HORN AND A TKOF TRIM POS WARNING ARE MANDATORY. A SWITCH GUARD WILL NOT SOLVE THE PROBLEM. THANKS FOR THE FIL EXPLAINING HOW TO DETECT TRIM DISPLACEMENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR IS CERTAIN THAT RUDDER TRIM INPUT WAS NOT COCKPIT ACTION INDUCED. HE OFFERS THE THEORY THAT THE PREVAILING WX CONDITIONS PRIMARILY RAIN MAY HAVE AFFECTED THE TRIM SWITCHES ALTHOUGH HE ADMITS THAT IT SEEMS UNLIKELY. THE CAPT IS CERTAIN THAT THE TRIM AND RUDDER POS WAS CENTERED WHEN CHKED DURING COCKPIT SETUP AND THAT THE MOVEMENT TOOK PLACE THEREAFTER. RPTR STATES THAT HE RECENTLY FLEW A BRAND NEW EXAMPLE OF THIS ACFT AND NOTED THAT IT HAD A MODIFIED TRIM ACTIVATION SYS SO THE PROB HAS BEEN ACTED ON TO SOME EXTENT BY THE ACFT MFR.

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.