Narrative:

During preflight, ran small amount of rudder trim in accordance with checklist. Rudder continued to run when knob was released instead of stopping. Trim knob did not return to center position. To stop the rudder, I rotated the knob to center. I noticed it was binding against the pedestal. We were able to pull up on the knob, which then worked normally. This problem was caught during an origination, but might not have been noticed during a clean-up inspection where the trim is checked to be at zero, which it was. We suspect a kit bag was placed on the pedestal when the preceding crew left the flight deck. Such a problem could easily go undetected until trim is needed after departure while low, slow, and heavy. It could also be misdiagnosed as an engine rollback or flight control asymmetry problem. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was a B767-200 overwater aircraft and was accomplishing the origination preflight check when the operation of the rudder trim knob was noted. The reporter said the trim knob would not return to the center spring loaded position after displacing the knob from center but continued to drive the trim actuator. The reporter said the knob jammed on the pedestal surface. The reporter stated this could be a problem on through flts where the checklist does not require checking trim knob operation. The reporter said the knob adjustment or lock screw appeared loose. The reporter stated the knob was reported at the next station but is not aware of the fix.

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Original NASA ASRS Text

Title: A B767-200 DURING THE OVERWATER PREFLT CHK IT WAS DISCOVERED THE RUDDER TRIM KNOB DID NOT RETURN TO THE SPRING LOADED CTR POS BUT CONTINUED TO DRIVE THE RUDDER TRIM.

Narrative: DURING PREFLT, RAN SMALL AMOUNT OF RUDDER TRIM IN ACCORDANCE WITH CHKLIST. RUDDER CONTINUED TO RUN WHEN KNOB WAS RELEASED INSTEAD OF STOPPING. TRIM KNOB DID NOT RETURN TO CTR POS. TO STOP THE RUDDER, I ROTATED THE KNOB TO CTR. I NOTICED IT WAS BINDING AGAINST THE PEDESTAL. WE WERE ABLE TO PULL UP ON THE KNOB, WHICH THEN WORKED NORMALLY. THIS PROB WAS CAUGHT DURING AN ORIGINATION, BUT MIGHT NOT HAVE BEEN NOTICED DURING A CLEAN-UP INSPECTION WHERE THE TRIM IS CHKED TO BE AT ZERO, WHICH IT WAS. WE SUSPECT A KIT BAG WAS PLACED ON THE PEDESTAL WHEN THE PRECEDING CREW LEFT THE FLT DECK. SUCH A PROB COULD EASILY GO UNDETECTED UNTIL TRIM IS NEEDED AFTER DEP WHILE LOW, SLOW, AND HVY. IT COULD ALSO BE MISDIAGNOSED AS AN ENG ROLLBACK OR FLT CTL ASYMMETRY PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A B767-200 OVERWATER ACFT AND WAS ACCOMPLISHING THE ORIGINATION PREFLT CHK WHEN THE OP OF THE RUDDER TRIM KNOB WAS NOTED. THE RPTR SAID THE TRIM KNOB WOULD NOT RETURN TO THE CTR SPRING LOADED POS AFTER DISPLACING THE KNOB FROM CTR BUT CONTINUED TO DRIVE THE TRIM ACTUATOR. THE RPTR SAID THE KNOB JAMMED ON THE PEDESTAL SURFACE. THE RPTR STATED THIS COULD BE A PROB ON THROUGH FLTS WHERE THE CHKLIST DOES NOT REQUIRE CHKING TRIM KNOB OP. THE RPTR SAID THE KNOB ADJUSTMENT OR LOCK SCREW APPEARED LOOSE. THE RPTR STATED THE KNOB WAS RPTED AT THE NEXT STATION BUT IS NOT AWARE OF THE FIX.

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.