A B737-300 WAS DISPATCHED WITH THE #2 ENG FAN BLADE DAMPERS INSTALLED IMPROPERLY CAUSING ENG VIBRATION.

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ACFT XYZ. I WORKED ON A JOB/JOB CARD TO INSTALL FAN BLADES ON #2 ENG OF THIS ACFT XYZ. MY PART OF THE JOB WAS TO CHK THAT THE FAN BLADE DAMPERS; SPACERS; RETAINERS AND BLADES WERE INSTALLED CORRECTLY. I ALSO INSTALLED THE REAR AND FRONT SPINNER CONE. ON NOV/XZ/98 THIS ACFT DEVELOPED AN ENG VIBRATION. THE BLADES WERE REMOVED AND UPON REMOVAL FOUND ALL 38 ACFT XYZ BLADE DAMPERS INCORRECTLY INSTALLED. MY SIGNOFF ON THE JOB ONLY PERMITTED ME TO SEE THE FRONT OF THE BLADES AND DAMPERS AS THEY WERE ALL INSTALLED WITH RETAINERS AND SPACERS. I BELIEVE TO THE BEST OF MY KNOWLEDGE THAT THE DAMPERS WERE INSTALLED PER THE JOB CARD IN QUESTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATES THE ENG FAN RETENTION INSTALLATION WAS CHECKED BY THE RPTR AFTER THE INSTALLATION WAS ACCOMPLISHED BY ANOTHER MECH. THE RPTR SAID THE CHECK IS MADE LOOKING AT THE FACE OF THE FAN DISK AND ONLY LOOKING AT THE END OF THE PARTS WHICH WOULD NOT REVEAL ANY INCORRECT DAMPER INSTALLATION. THE RPTR STATED THE JOB CARD TO INSTALL THE DAMPERS HAS NO DRAWINGS OR VISUAL AIDS TO PREVENT THE INCORRECT INSTALLATION BUT THE MAINT MANUAL HAS CLEAR INSTRUCTIONS AND GOOD VISUAL AIDS. THE MAINT MANUAL WAS NOT USED IN THIS CASE.