Narrative:

Small aircraft X was level 4000 swbound established on V20. I had to call mob approach to get position verification due to aircraft in coast and non-ARTS track update. Small aircraft X stayed in coast for approximately 10-15 mi. Altitude was verified level 4000. Air carrier Y was a commuter light transport descending out of 5000 for 3000. Air carrier Y wanted to turn right to bfm VORTAC for a better approach to mobile. Air carrier Y was frequency changed prior to being level at 3000. Aircraft appeared to be 4 mi apart. I turned small aircraft X heading 280 to ensure separation. Mobile called and reported the aircraft appeared closer than 3 mi. Houston was called and aircraft were no closer than 2 3/4 mi at 5000 ft. I should have applied better or more positive control between the aircraft. Another problem we have been having that was happening with small aircraft X is constant coasting. Even though beacon channels were switched the same aircraft continued to coast. Small aircraft X altitude also fluctuated even though altitude was verified and mobile approach indicated 4000 with a good tag and altitude. Another factor effecting the system has to do with aircraft handed off to another facility. You cannot move their data tags without moving all of them. (This is with the ARTS iia). At the time an aircraft at 8500 climbing to 9000 was over the coast tag which was in handoff status to high radar to hold the tag on radar. All these tags overlapped at time of incident.

Related reports:

Google
 

Original NASA ASRS Text

Title: SMA X HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: SMA X WAS LEVEL 4000 SWBOUND ESTABLISHED ON V20. I HAD TO CALL MOB APCH TO GET POS VERIFICATION DUE TO ACFT IN COAST AND NON-ARTS TRACK UPDATE. SMA X STAYED IN COAST FOR APPROX 10-15 MI. ALT WAS VERIFIED LEVEL 4000. ACR Y WAS A COMMUTER LTT DSNDING OUT OF 5000 FOR 3000. ACR Y WANTED TO TURN R TO BFM VORTAC FOR A BETTER APCH TO MOBILE. ACR Y WAS FREQ CHANGED PRIOR TO BEING LEVEL AT 3000. ACFT APPEARED TO BE 4 MI APART. I TURNED SMA X HDG 280 TO ENSURE SEPARATION. MOBILE CALLED AND RPTED THE ACFT APPEARED CLOSER THAN 3 MI. HOUSTON WAS CALLED AND ACFT WERE NO CLOSER THAN 2 3/4 MI AT 5000 FT. I SHOULD HAVE APPLIED BETTER OR MORE POSITIVE CTL BTWN THE ACFT. ANOTHER PROBLEM WE HAVE BEEN HAVING THAT WAS HAPPENING WITH SMA X IS CONSTANT COASTING. EVEN THOUGH BEACON CHANNELS WERE SWITCHED THE SAME ACFT CONTINUED TO COAST. SMA X ALT ALSO FLUCTUATED EVEN THOUGH ALT WAS VERIFIED AND MOBILE APCH INDICATED 4000 WITH A GOOD TAG AND ALT. ANOTHER FACTOR EFFECTING THE SYS HAS TO DO WITH ACFT HANDED OFF TO ANOTHER FACILITY. YOU CANNOT MOVE THEIR DATA TAGS WITHOUT MOVING ALL OF THEM. (THIS IS WITH THE ARTS IIA). AT THE TIME AN ACFT AT 8500 CLBING TO 9000 WAS OVER THE COAST TAG WHICH WAS IN HDOF STATUS TO HIGH RADAR TO HOLD THE TAG ON RADAR. ALL THESE TAGS OVERLAPPED AT TIME OF INCIDENT.

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.