Narrative:

The occurrence: in-flight, 3 degree rudder trim required to maintain level flight. The direct cause found when aircraft returned to field: test jumper left in yaw damper causing right rudder deflection. The series of events leading to problem were as follows: during third shift, routine overnight maintenance the previous night, the rudder PCU internal leak test engineering order was started. The mechanics had difficulty with the test. As I took over the job on second shift, I began by reading the service letter (wxxxw). Neither the engineering order nor the service letter explained how to hook up the test meter or what settings to use. After a frustrating 1.5 to 2 hours attempting to obtain the instructions from company maintenance control, engineering, workload planning and other avenues, I finally called a former maintenance station I had worked at to facsimile me the instructions. They had them in a quick reference folder. The test equipment instructions originated in another job card for hydraulic leak rate tests. By this point in time, I now was working alone, and with the test meter instructions, the engineering order and the service letter in hand, I began the test using mainly the service letter. While the engineering order had blocks to check off each step, it was different from the service letter. The service letter had no chkoff blocks. I proceeded with the test and it checked out good. However, several times in the test a jumper is installed and removed from the yaw damper. This deflects the rudder slightly. The final time I accidentally left the jumper in. This kept the rudder slightly to the right. After return to field, I replaced the yaw damper as a precaution.

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Original NASA ASRS Text

Title: A B737-200 WAS DISPATCHED IN NON COMPLIANCE WITH A TEST JUMPER WIRE INSTALLED IN THE YAW DAMPER COUPLER TEST PLUG.

Narrative: THE OCCURRENCE: INFLT, 3 DEG RUDDER TRIM REQUIRED TO MAINTAIN LEVEL FLT. THE DIRECT CAUSE FOUND WHEN ACFT RETURNED TO FIELD: TEST JUMPER LEFT IN YAW DAMPER CAUSING R RUDDER DEFLECTION. THE SERIES OF EVENTS LEADING TO PROB WERE AS FOLLOWS: DURING THIRD SHIFT, ROUTINE OVERNIGHT MAINT THE PREVIOUS NIGHT, THE RUDDER PCU INTERNAL LEAK TEST ENGINEERING ORDER WAS STARTED. THE MECHS HAD DIFFICULTY WITH THE TEST. AS I TOOK OVER THE JOB ON SECOND SHIFT, I BEGAN BY READING THE SVC LETTER (WXXXW). NEITHER THE ENGINEERING ORDER NOR THE SVC LETTER EXPLAINED HOW TO HOOK UP THE TEST METER OR WHAT SETTINGS TO USE. AFTER A FRUSTRATING 1.5 TO 2 HRS ATTEMPTING TO OBTAIN THE INSTRUCTIONS FROM COMPANY MAINT CTL, ENGINEERING, WORKLOAD PLANNING AND OTHER AVENUES, I FINALLY CALLED A FORMER MAINT STATION I HAD WORKED AT TO FAX ME THE INSTRUCTIONS. THEY HAD THEM IN A QUICK REF FOLDER. THE TEST EQUIP INSTRUCTIONS ORIGINATED IN ANOTHER JOB CARD FOR HYD LEAK RATE TESTS. BY THIS POINT IN TIME, I NOW WAS WORKING ALONE, AND WITH THE TEST METER INSTRUCTIONS, THE ENGINEERING ORDER AND THE SVC LETTER IN HAND, I BEGAN THE TEST USING MAINLY THE SVC LETTER. WHILE THE ENGINEERING ORDER HAD BLOCKS TO CHK OFF EACH STEP, IT WAS DIFFERENT FROM THE SVC LETTER. THE SVC LETTER HAD NO CHKOFF BLOCKS. I PROCEEDED WITH THE TEST AND IT CHKED OUT GOOD. HOWEVER, SEVERAL TIMES IN THE TEST A JUMPER IS INSTALLED AND REMOVED FROM THE YAW DAMPER. THIS DEFLECTS THE RUDDER SLIGHTLY. THE FINAL TIME I ACCIDENTALLY LEFT THE JUMPER IN. THIS KEPT THE RUDDER SLIGHTLY TO THE R. AFTER RETURN TO FIELD, I REPLACED THE YAW DAMPER AS A PRECAUTION.

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.