A B737-300 WAS RELEASED FOR SVC AFTER A #2 ENG CHANGE AND LATER DISCOVERED 1 AFT ENG MOUNT WASHER WAS INSTALLED INCORRECTLY.

Narrative

I WAS THE ASSIGNED INSPECTOR DURING AN ENG CHANGE #2 POSITION ACFT X ON OCT/SAT/05. AFTER THE ENG WAS UP AND TORQUED; INSPECTED THE MOUNTS AND FAILED TO NOTICE THAT THE AFT MOUNT WASHER WAS INSTALLED UPSIDE DOWN. THE AMT THAT INSTALLED IT REALIZED THE ERROR 1 WK LATER ON ANOTHER ENG CHANGE; AND RPTED THAT HE MADE THE ERROR ON ACFT X #2 ENG. I WAS AWARE OF THE REQUIREMENT OF THE WASHER'S POS; BUT I HAD NOT BEEN INVOLVED IN AN ENG CHANGE OF THIS TYPE FOR WHAT I BELIEVE TO BE 2 YRS; AND DIDN'T HAVE THE PRESENCE OF MIND WHEN I WAS INSPECTING THE MOUNTS AFTER THE TORQUE WAS COMPLETED TO BE LOOKING TO SEE IF THE WASHER WAS INSTALLED PROPERLY. I NOTICED IT WAS IN PLACE AND NOT MISSING. THE WASHER HAS A CHAMBER ON ONE SIDE THAT IS USED TO HOLD A TOOL IN PLACE THAT KEEPS THE WRENCH IN THE PROPER POS WHILE TORQUE IS APPLIED (SO THE WRENCH WON'T SLIP OFF THE NUT). IT WAS LATER DETERMINED BY THE ENGINEERING DEPT THAT THE NUT AND WASHER COMBINATION AS IS POSES NO SAFETY OF FLT CONCERNS. A REPAIR AUTH WAS WRITTEN ALLOWING THE ACFT TO BE OPERATED IN THIS CONDITION. THE ALTERNATIVE WAS TO REMOVE THE ENG AND CHANGE THE MOUNTS. THIS COULD HAVE LED TO UNNEEDED COSTS TO MY COMPANY AT A TIME WHEN WE CAN LEAST AFFORD TO BE WORKING AVOIDABLE MISTAKES.