A B737-800 INSPECTOR RPTS THAT DURING A CONTRACT FACILITY 'C' CHK; A #1 ENG REQUIRED FAN BLADE WT RPT WAS SIGNED OFF AS ACCOMPLISHED BUT WAS NOT DONE.

Narrative

WHILE PERFORMING A L ENG CFM FAN BLADE ROOT INSPECTION JOB CARD ON A B737-800 DURING A 'C' CHK MAINT VISIT; THE COMPUTER MAPPING TASK; WHICH INCORPORATES SENDING BLADE WT/MOMENT DATA TO ENGINEERING; WAS SIGNED FOR BUT NOT ACCOMPLISHED DUE TO AN INTERP ERROR OF THE JOB CARD. NO FAN BLADES WERE REPLACED ON THE #1 ENG DURING THE VISIT AND THE FAN BLADE VIBRATION HISTORY INDICATED THAT THE VIBRATION LEVELS OF THE BLADES WERE WITHIN CUSTOMER SATISFACTORY LEVELS. IT WAS ERRONEOUSLY INTERPED THAT A NEW BLADE MAPPING WAS NOT REQUIRED BECAUSE NO BLADES WERE REPLACED. THEREFORE; NO WTS OR MOMENTS WERE CHANGED. THE JOB CARD; HOWEVER; STATES THAT DURING 'C' CHK LEVEL OR HIGHER MAINT VISITS; FAN BLADE MAPPING IS REQUIRED. THE ACFT'S #1 ENG PASSED THE OPERATOR'S VIBRATION SURVEY MAINT MANUAL TASK AND NO REBALANCE WAS REQUIRED. MAKING REVISIONS TO THE JOB CARD TO GIVE MORE DIRECT GUIDANCE OF OPERATOR'S PROCESSES AND PROCS; WHEN THIRD PARTY MAINT IS BEING PERFORMED; WOULD GREATLY HELP REDUCE THE LIKELIHOOD OF THIS ERROR RECURRING.