|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||airport : day.airport|
|Altitude||agl single value : 0|
|Operator||common carrier : air carrier|
|Make Model Name||Challenger CL600|
|Operating Under FAR Part||Part 121|
|Flight Phase||ground : preflight|
ground : parked
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Qualification||pilot : commercial|
|Anomaly||aircraft equipment problem : critical|
maintenance problem : improper maintenance
|Independent Detector||other flight crewa|
Maintenance Human Performance
|Primary Problem||Maintenance Human Performance|
Arrived for the morning flight. Received aircraft from overnight maintenance work. Performed all preflight duties per poh. While waiting for final ACARS takeoff data to return; I attempted to set the pitch trim to an approximately value for the loading conditions. Upon activation of the first officer pitch trim switch; I discovered the trim moved in the opposite direction of that commanded by the switch. I confirmed this action with the captain who also observed the incorrect movement of the pitch trim motor. We immediately contacted maintenance and proceeded to deplane passenger due to the length of the predicted delay. Upon review of the problem by maintenance personnel; it was discovered the trim switch was wired incorrectly. The wiring resulted in opposite activation of the trim motor (ie; commanded nose up; trim moved nose down). The maintenance personnel were able to correct wiring of the switch and allowed for the aircraft to be returned to service. This situation highlighted 2 areas of concern. Per the current poh; there is not a designated procedure in which the first officer checks the operation of the control yoke mounted trim switch. This problem was discovered prior to block out only because I attempted to set an approximately trim setting. Secondly. This aircraft had just come out of aircraft maintenance. The ACARS indicated the aircraft flew a leg the prior night and was then returned to the terminal following overnight maintenance. This issue clearly resulted from a breakdown in the inspection system. I am confused as to how the trim switches could be worked on by a maintenance technician and then returned to service with an airworthiness signoff without an operations check of the system. The first time the switch was activated at the gate this problem was idented. It was clearly a wiring error and not an intermittent problem this leg was scheduled to be operated by the first officer and it was very possible this first time the trim switch would be operated would be after aircraft rotation and relatively close to the ground. Callback conversation with reporter revealed the following information: reporter stated that it is not a requirement that the first officer check or activate the trim switch at any time prior to takeoff. Since the anomaly was restricted to the trim switch; it would not have been discovered until airborne.
Original NASA ASRS Text
Title: BOMBARDIER CL600 FO DISCOVERED HIS PITCH TRIM SWITCH ACTIVATED THE TRIM IN THE OPPOSITE DIRECTION OF THAT COMMANDED BY THE SWITCH.
Narrative: ARRIVED FOR THE MORNING FLT. RECEIVED ACFT FROM OVERNIGHT MAINT WORK. PERFORMED ALL PREFLT DUTIES PER POH. WHILE WAITING FOR FINAL ACARS TKOF DATA TO RETURN; I ATTEMPTED TO SET THE PITCH TRIM TO AN APPROX VALUE FOR THE LOADING CONDITIONS. UPON ACTIVATION OF THE FO PITCH TRIM SWITCH; I DISCOVERED THE TRIM MOVED IN THE OPPOSITE DIRECTION OF THAT COMMANDED BY THE SWITCH. I CONFIRMED THIS ACTION WITH THE CAPT WHO ALSO OBSERVED THE INCORRECT MOVEMENT OF THE PITCH TRIM MOTOR. WE IMMEDIATELY CONTACTED MAINT AND PROCEEDED TO DEPLANE PAX DUE TO THE LENGTH OF THE PREDICTED DELAY. UPON REVIEW OF THE PROB BY MAINT PERSONNEL; IT WAS DISCOVERED THE TRIM SWITCH WAS WIRED INCORRECTLY. THE WIRING RESULTED IN OPPOSITE ACTIVATION OF THE TRIM MOTOR (IE; COMMANDED NOSE UP; TRIM MOVED NOSE DOWN). THE MAINT PERSONNEL WERE ABLE TO CORRECT WIRING OF THE SWITCH AND ALLOWED FOR THE ACFT TO BE RETURNED TO SVC. THIS SITUATION HIGHLIGHTED 2 AREAS OF CONCERN. PER THE CURRENT POH; THERE IS NOT A DESIGNATED PROC IN WHICH THE FO CHKS THE OP OF THE CTL YOKE MOUNTED TRIM SWITCH. THIS PROB WAS DISCOVERED PRIOR TO BLOCK OUT ONLY BECAUSE I ATTEMPTED TO SET AN APPROX TRIM SETTING. SECONDLY. THIS ACFT HAD JUST COME OUT OF ACFT MAINT. THE ACARS INDICATED THE ACFT FLEW A LEG THE PRIOR NIGHT AND WAS THEN RETURNED TO THE TERMINAL FOLLOWING OVERNIGHT MAINT. THIS ISSUE CLRLY RESULTED FROM A BREAKDOWN IN THE INSPECTION SYS. I AM CONFUSED AS TO HOW THE TRIM SWITCHES COULD BE WORKED ON BY A MAINT TECHNICIAN AND THEN RETURNED TO SVC WITH AN AIRWORTHINESS SIGNOFF WITHOUT AN OPS CHK OF THE SYS. THE FIRST TIME THE SWITCH WAS ACTIVATED AT THE GATE THIS PROB WAS IDENTED. IT WAS CLRLY A WIRING ERROR AND NOT AN INTERMITTENT PROB THIS LEG WAS SCHEDULED TO BE OPERATED BY THE FO AND IT WAS VERY POSSIBLE THIS FIRST TIME THE TRIM SWITCH WOULD BE OPERATED WOULD BE AFTER ACFT ROTATION AND RELATIVELY CLOSE TO THE GND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT IT IS NOT A REQUIREMENT THAT THE FO CHECK OR ACTIVATE THE TRIM SWITCH AT ANY TIME PRIOR TO TKOF. SINCE THE ANOMALY WAS RESTRICTED TO THE TRIM SWITCH; IT WOULD NOT HAVE BEEN DISCOVERED UNTIL AIRBORNE.
Data retrieved from NASA's ASRS site as of January 2009 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.