Narrative:

Second aircraft was atx X cargo aircraft inbound to geg, light transport Y outbound. Atx X tagged up on radar as a VFR small aircraft from an old flight plan remaining in the ARTS ii a computer. Center controller indicated to geg east radar controller that atx X was 4 mi east of small aircraft tag. I was working light transport Y opposite direction on geg west radar. As small aircraft tag continued nebound, approaching light transport Y I suspected something was wrong as it continued inbound on departure centerline and showed a gndspd too high for an small aircraft. I was busy simultaneously with a military operation, but instructed the light transport Y to descend to 5000 immediately. The east controller simultaneously realized the small aircraft tag was actually the atx X and turned it eastbound. Both aircraft saw the other visually. Seattle center controller should never have issued the position of the unidented atx X as east of a named target he did not have displayed on his scope (the small aircraft). When the host computer drops a flight plan (as it had the small aircraft), it is imperative that it also drop it from any associated ARTS system so that an aircraft later assigned the same code cannot tag to a previous unknown aircraft flight plan. 'Identify' and code-readout checks by controllers on any and all questionable targets should be performed religiously. Supplemental information from acn 221891. Center was unable to handoff atx X. I told them I was busy and would call them back. Center asked if they could keep him coming and I said yes. Then I called back and asked where atx X position was reference a VFR data block, they said he was 4 mi east of him then they asked if they could terminate and ship him, I agreed. I turned up my primary radar to look for a primary and told west radar I had an atx X to the south at 60 and did not know where he was. Atx X checked on and I asked him his altitude DME and radial, which he gave. His position was where the VFR small aircraft data block was. I quick looked his beacon code and it was the same as atx X code. Then recognizing that the VFR data block was really atx X I gave him traffic and turned him. He told me he had the traffic in sight. I told him to maintain visual separation. The traffic for atx X was being worked by the west controller and there was a loss of separation. It appears that the flight plan on the VFR small aircraft was drop from the ctrs computer but not from ours so atx X tagged up as small aircraft.

Related reports:

Google
 

Original NASA ASRS Text

Title: APCH CTLR MISIDENTED ACFT (ATX X AND SMA). ATX X HAD LTSS FROM LTT Y. SYS ERROR.

Narrative: SECOND ACFT WAS ATX X CARGO ACFT INBOUND TO GEG, LTT Y OUTBOUND. ATX X TAGGED UP ON RADAR AS A VFR SMA FROM AN OLD FLT PLAN REMAINING IN THE ARTS II A COMPUTER. CTR CTLR INDICATED TO GEG E RADAR CTLR THAT ATX X WAS 4 MI E OF SMA TAG. I WAS WORKING LTT Y OPPOSITE DIRECTION ON GEG W RADAR. AS SMA TAG CONTINUED NEBOUND, APCHING LTT Y I SUSPECTED SOMETHING WAS WRONG AS IT CONTINUED INBOUND ON DEP CTRLINE AND SHOWED A GNDSPD TOO HIGH FOR AN SMA. I WAS BUSY SIMULTANEOUSLY WITH A MIL OP, BUT INSTRUCTED THE LTT Y TO DSND TO 5000 IMMEDIATELY. THE E CTLR SIMULTANEOUSLY REALIZED THE SMA TAG WAS ACTUALLY THE ATX X AND TURNED IT EBOUND. BOTH ACFT SAW THE OTHER VISUALLY. SEATTLE CTR CTLR SHOULD NEVER HAVE ISSUED THE POS OF THE UNIDENTED ATX X AS E OF A NAMED TARGET HE DID NOT HAVE DISPLAYED ON HIS SCOPE (THE SMA). WHEN THE HOST COMPUTER DROPS A FLT PLAN (AS IT HAD THE SMA), IT IS IMPERATIVE THAT IT ALSO DROP IT FROM ANY ASSOCIATED ARTS SYS SO THAT AN ACFT LATER ASSIGNED THE SAME CODE CANNOT TAG TO A PREVIOUS UNKNOWN ACFT FLT PLAN. 'IDENT' AND CODE-READOUT CHKS BY CTLRS ON ANY AND ALL QUESTIONABLE TARGETS SHOULD BE PERFORMED RELIGIOUSLY. SUPPLEMENTAL INFO FROM ACN 221891. CTR WAS UNABLE TO HDOF ATX X. I TOLD THEM I WAS BUSY AND WOULD CALL THEM BACK. CTR ASKED IF THEY COULD KEEP HIM COMING AND I SAID YES. THEN I CALLED BACK AND ASKED WHERE ATX X POS WAS REF A VFR DATA BLOCK, THEY SAID HE WAS 4 MI E OF HIM THEN THEY ASKED IF THEY COULD TERMINATE AND SHIP HIM, I AGREED. I TURNED UP MY PRIMARY RADAR TO LOOK FOR A PRIMARY AND TOLD W RADAR I HAD AN ATX X TO THE S AT 60 AND DID NOT KNOW WHERE HE WAS. ATX X CHKED ON AND I ASKED HIM HIS ALT DME AND RADIAL, WHICH HE GAVE. HIS POS WAS WHERE THE VFR SMA DATA BLOCK WAS. I QUICK LOOKED HIS BEACON CODE AND IT WAS THE SAME AS ATX X CODE. THEN RECOGNIZING THAT THE VFR DATA BLOCK WAS REALLY ATX X I GAVE HIM TFC AND TURNED HIM. HE TOLD ME HE HAD THE TFC IN SIGHT. I TOLD HIM TO MAINTAIN VISUAL SEPARATION. THE TFC FOR ATX X WAS BEING WORKED BY THE W CTLR AND THERE WAS A LOSS OF SEPARATION. IT APPEARS THAT THE FLT PLAN ON THE VFR SMA WAS DROP FROM THE CTRS COMPUTER BUT NOT FROM OURS SO ATX X TAGGED UP AS SMA.

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.