Narrative:

I was working the arrival east radar position when air carrier X checked on my frequency. The ARTS failed on the position, the supervisor reconfigured the position which brought the ARTS back up. Within 30 seconds it failed again. This happened twice more within a 3 min period. I chose to move to another scope and started working traffic from the arrival west radar position. I descended air carrier X to 10000 ft and set up the rest of my traffic to give me time to make all the necessary adjustments and changes to the new position. I proceeded to set up the new position and was not able to visually scan the radar scope during this transition period. Air carrier X reported a TCASII resolution and climbed to avoid the traffic. I observed a VFR target at air carrier X altitude merging with the aircraft. Due to the equipment malfunction I was not able to observe the VFR target and issue a safety alert to the aircraft. The failure of the ARTS on the arrival east radar position has been occurring over the last 3 weeks, maintenance and data system specialist have been working on the problem but have not been able to pinpoint it as of yet. I believe we should not have been working the traffic from that position knowing the equipment failure possibility.

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Original NASA ASRS Text

Title: ACR X HAD NMAC TCASII RA CLB WITH VFR ACFT ABOVE TCA. SEE AND AVOID CONCEPT. EVASIVE ACTION TAKEN.

Narrative: I WAS WORKING THE ARR E RADAR POS WHEN ACR X CHKED ON MY FREQ. THE ARTS FAILED ON THE POS, THE SUPVR RECONFIGURED THE POS WHICH BROUGHT THE ARTS BACK UP. WITHIN 30 SECONDS IT FAILED AGAIN. THIS HAPPENED TWICE MORE WITHIN A 3 MIN PERIOD. I CHOSE TO MOVE TO ANOTHER SCOPE AND STARTED WORKING TFC FROM THE ARR W RADAR POS. I DSNDED ACR X TO 10000 FT AND SET UP THE REST OF MY TFC TO GIVE ME TIME TO MAKE ALL THE NECESSARY ADJUSTMENTS AND CHANGES TO THE NEW POS. I PROCEEDED TO SET UP THE NEW POS AND WAS NOT ABLE TO VISUALLY SCAN THE RADAR SCOPE DURING THIS TRANSITION PERIOD. ACR X RPTED A TCASII RESOLUTION AND CLBED TO AVOID THE TFC. I OBSERVED A VFR TARGET AT ACR X ALT MERGING WITH THE ACFT. DUE TO THE EQUIP MALFUNCTION I WAS NOT ABLE TO OBSERVE THE VFR TARGET AND ISSUE A SAFETY ALERT TO THE ACFT. THE FAILURE OF THE ARTS ON THE ARR E RADAR POS HAS BEEN OCCURRING OVER THE LAST 3 WKS, MAINT AND DATA SYS SPECIALIST HAVE BEEN WORKING ON THE PROBLEM BUT HAVE NOT BEEN ABLE TO PINPOINT IT AS OF YET. I BELIEVE WE SHOULD NOT HAVE BEEN WORKING THE TFC FROM THAT POS KNOWING THE EQUIP FAILURE POSSIBILITY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.