A B737-800 ON A FUNCTIONAL TEST FLT USED INCORRECT DATA TO TRIM THE ACFT CAUSED BY CONFLICT BTWN THE B737-800 PREFLT HANDBOOK AND THE MAINT MANUAL PROCS.

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I'M AN ACFT INSPECTOR WITH ACR. ONE OF MY DUTIES IS TO ASSIST IN PERFORMING FUNCTIONAL CHK FLTS. I WAS RECENTLY INVOLVED IN JUST SUCH A TASK ON 3 OF ACR B737-800 SERIES ACFT. THE FUNCTIONAL CHK FLTS WERE REQUIRED DUE TO ELEVATOR TAB REPLACEMENTS. I PERFORMED THESE FUNCTIONAL CHK FLT TASKS USING THE COMPANY'S B737-800 PREFLT HANDBOOK. THE TEST REQUIRED WAS AN ELEVATOR PWR OFF FLT TEST. THIS WAS ALL TO COMPANY POLICIES AND PROCS TO THE BEST OF MY KNOWLEDGE. THE FIRST FUNCTIONAL CHK FLTS WAS ACCOMPLISHED ON ACFT XYZ ON AUG/SUN/99. THE ACFT FAILED TO MEET THE GUIDELINES SET OUT BY THE PREFLT HANDBOOK. A DISCREPANCY WAS ENTERED INTO THE ACFT LOGBOOK. I WAS NOT INVOLVED WITH THE ENSUING FUNCTIONAL CHK FLTS ON THIS ACFT. THE SECOND FUNCTIONAL CHK FLT WAS ACCOMPLISHED ON ACFT ABC ON AUG/MON/99. THE ACFT FAILED TO MEET THE PREFLT HANDBOOK TEST REQUIREMENTS. WE LANDED; HYD MAINT MECHS ADJUSTED THE ELEVATOR TABS PER THE ACFT MAINT MANUAL A/T AND SO DOCUMENTED. WE PERFORMED A SECOND FUNCTIONAL CHK FLT ON THIS SAME ACFT WITH GOOD RESULTS. I SIGNED THE ACFT LOG CORRECTIVE ACTION AS COMPLIED WITH FUNCTIONAL CHK FLT ELEVATOR PWR OFF TEST GOOD. THE THIRD FUNCTIONAL CHK FLT WAS ACCOMPLISHED ON ACFT XXX ON AUG/TUE/99. THIS ACFT FAILED TO MEET THE PREFLT HANDBOOK TEST REQUIREMENTS. A DISCREPANCY WAS ENTERED INTO THE ACFT LOG BOOK. I WAS NOT INVOLVED WITH THE ENSUING FCF'S ON THIS ACFT. AFTER THE FCF'S OF 08/TUES/1999 ON ACFT XXX. THE AIR CREW AND I HAD DISCUSSION ABOUT THE PREFLT HANDBOOK PROCS FOR THIS TEST -- PRIMARILY ON A COUPLE OF ITEMS THAT SHOULD BE CHANGED IN THE PREFLT HANDBOOK TEST FLT PROCS. I EXPLAINED THAT I WOULD RESEARCH THESE ITEMS AND SUBMIT A REQUEST TO CHANGE IN THE PREFLT HANDBOOK ACCORDINGLY. ON AUG/THU/99 I SPENT AN EXHAUSTING AMOUNT OF TIME RESEARCHING OUR ELECTRONIC TECHNICAL MANUAL AND TEST PROGRAM FOR THE B737-800. SEVERAL PLACES I FOUND A REF TO THIS ELEVATOR PWR OFF FLT TEST. THE REF WAS ALWAYS ACFT MAINT MANUAL. THIS DID NOT EXIST. AFTER THIS RESEARCH; I NOTIFIED MY FOREMAN WHAT I HAD FOUND; OR COULD NOT FIND. HE PUT A CALL INTO TECHNICAL PROCS FOR CONFIRMATION ON THIS TEST REQUIREMENT. WHAT WE FOUND OUT WAS THAT THE TEST WAS NOT IN OUR ACR ACFT MAINT MANUAL. HOWEVER; THERE WAS A REVISION IN FROM BOEING TO OUR ACFT MAINT MANUAL WITH THIS TEST; THAT WAS NOT AVAILABLE TO US. THE ELEVATOR PWR OFF TEST FLT PROC AND PROFILE WAS CONSIDERABLY DIFFERENT. NOT ONLY REQUIRING A CHANGE TO OUR PREFLT HANDBOOK; BUT THAT THE TASKS I HAD PERFORMED WERE NOT CORRECT. ACR TECHNICAL OPS QUALITY ASSURANCE DEPT GOT INVOLVED AND SET IN MOTION THE PROPER ACTION FOR THE ACFT EFFECTED. WE NOW HAVE AUTH TO USE THE BOEING ACFT MAINT MANUAL TASK. THIS ACFT MAINT MANUAL WAS NOT AUTH FOR USE AT THE TIME OF OUR FUNCTIONAL CHK FLTS MENTIONED IN THIS LETTER. THEY WERE NOT LEGAL ACR DOCUMENTS TO USE FOR THE ELEVATOR PWR OFF FLT TEST. I USED THE PREFLT HANDBOOK FOR THE TASK REQUIRED WHICH IS THE PROC PER FLT OPS MANUAL.