AN ATR72-200 HAD A MODIFICATION WHICH REQUIRED INSTALLING 2 PLUGS IN THE AIR CONDITIONING DISTRIBUTION DUCTS. DISCOVERED ONLY 1 PLUG INSTALLED.

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PERFORMED ACFT MODIFICATION AIR CONDITIONING CABIN AIR DISTRIBUTION SYS PLUG INSTALLATION VERIFICATION ON NOV/WED/06 ON ACFT X AS TOLD BY SUPVR. I WAS CALLED TO OFFICE A FEW DAYS LATER REGARDING ABOVE MODIFICATION COMPLETION. IT WAS FOUND THAT ONLY ONE OF THE PLUGS CALLED ON MODIFICATION WAS INSTALLED. AT THE TIME I PERFORMED THE MODIFICATION FOR FIRST TIME; I WAS TOLD THAT I NEEDED TO BLOCK THE OPEN END DUCT; AS MENTIONED ON ITEM 4 ON MODIFICATION ITEM 5 STATES TO VERIFY THE INSTALLATION OF OTHER PLUG. I LOOKED AROUND AREA AND I DID NOT NOTICE OTHER BLOCKING CAP ATTACHED TO STRUCTURE. LOOKING AT PICTURE ON MODIFICATION; DID NOT NOTICE ANY OTHER OPEN DUCT; SO I ASSUMED THAT ITEM 5 IS ALREADY BLOCKED; BUT WHEN CALLED TO OFFICE; MY SUPVR TOLD ME THAT UPON CHKING AT ANOTHER STATION WHILE PERFORMED A CHK; IT WAS DISCOVERED THAT PLUG WAS STILL INSTALLED AT STRUCTURE; NOT TO DUCT; THEREFORE; THE DISCREPANCY. I HAD HARD TIME UNDERSTANDING MODIFICATION BECAUSE IS NOT STATING TO TAKE APART THE DUCTS ATTACHED TOGETHER IN ORDER TO BE ABLE TO VERIFY INSTALLATION OF PLUG. ALSO THE AREA OF CONCERN IS COMPLETED WITH INSULATION BLANKETS AND AS I MENTIONED; I DID NOT SEE ANY PLUG ATTACHED TO STRUCTURE SO I ASSUMED THAT ITEM IS ALREADY INSTALLED. I WOULD LIKE TO SEE THIS MODIFICATION TO BE DESCRIBED IN A BETTER WAY IN ORDER TO AVOID CONFUSION AS THE ONE IN THIS CASE. I'M ALSO CONCERNED BECAUSE I WORKED 2 OTHER ACFT; ALTHOUGH THIS OTHER I BELIEVE I WORKED TOGETHER WITH OTHER MECH. PLEASE TAKE NOTE OF THIS MODIFICATION BECAUSE IS NOT EXPLAINED CORRECTLY THE VERIFICATION PROCESS INCLUDING ITEMS THAT NEED POSSIBLE REMOVAL; LIKE DUCTS AND INSULATION BLANKETS; TO PERFORM MODIFICATION CORRECTLY.