Narrative:

While working ardr 3 east radar, I observed the possible loss of separation between small transport X and small aircraft Y. Small transport X was inbound landing csg when his mode C dropped off my radar presentation. At this time I was also working small aircraft Y eastbound at 7000'. After initial contact on small transport X, I issued an altitude of 5000'. Approximately 4-5 mins later, I observed the altitude (mode C) on small transport X return, and it indicated 7400 descending. At this time the small transport X was approximately 3 mi nne of the small aircraft Y. I immediately turned the small transport X and the small aircraft Y to keep from possibly losing separation. The pilot of the small aircraft Y questioned me stating that he thought the small transport X was closer. Supplemental information from acn 136109: the airspace presently occupied by small aircraft Y. These 2 radar targets merged with mode C readouts indicating small transport X to be 200' below the small aircraft Y. Supplemental information from acn 136105: small transport X was inbound to csg from the northeast. Small aircraft Y was eastbound at 7000. Small transport X was descending on converging course. Evidently his mode C quit functioning for a few sweeps. When the radar controller saw the conflict it was too late to achieve legal separation. The evasive action prescribed by the controller was wrong and caused the 2 aircraft to pass even closer. The targets merged at near the same altitude. I was working flight data at the time of the occurrence. The sector was busy. Application of good vectoring or altitude separation would have prevented the occurrence. The pilot of the small aircraft Y said the right turn prescribed by the controller would have put him right in the small transport X's propellers.

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Original NASA ASRS Text

Title: SMT X HAD LESS THAN STANDARD SEPARATION FROM SMA Y. SYSTEM ERROR. NMAC.

Narrative: WHILE WORKING ARDR 3 EAST RADAR, I OBSERVED THE POSSIBLE LOSS OF SEPARATION BETWEEN SMT X AND SMA Y. SMT X WAS INBND LNDG CSG WHEN HIS MODE C DROPPED OFF MY RADAR PRESENTATION. AT THIS TIME I WAS ALSO WORKING SMA Y EBND AT 7000'. AFTER INITIAL CONTACT ON SMT X, I ISSUED AN ALT OF 5000'. APPROX 4-5 MINS LATER, I OBSERVED THE ALT (MODE C) ON SMT X RETURN, AND IT INDICATED 7400 DESCENDING. AT THIS TIME THE SMT X WAS APPROX 3 MI NNE OF THE SMA Y. I IMMEDIATELY TURNED THE SMT X AND THE SMA Y TO KEEP FROM POSSIBLY LOSING SEPARATION. THE PLT OF THE SMA Y QUESTIONED ME STATING THAT HE THOUGHT THE SMT X WAS CLOSER. SUPPLEMENTAL INFORMATION FROM ACN 136109: THE AIRSPACE PRESENTLY OCCUPIED BY SMA Y. THESE 2 RADAR TARGETS MERGED WITH MODE C READOUTS INDICATING SMT X TO BE 200' BELOW THE SMA Y. SUPPLEMENTAL INFORMATION FROM ACN 136105: SMT X WAS INBND TO CSG FROM THE NE. SMA Y WAS EBND AT 7000. SMT X WAS DESCENDING ON CONVERGING COURSE. EVIDENTLY HIS MODE C QUIT FUNCTIONING FOR A FEW SWEEPS. WHEN THE RADAR CTLR SAW THE CONFLICT IT WAS TOO LATE TO ACHIEVE LEGAL SEPARATION. THE EVASIVE ACTION PRESCRIBED BY THE CTLR WAS WRONG AND CAUSED THE 2 ACFT TO PASS EVEN CLOSER. THE TARGETS MERGED AT NEAR THE SAME ALT. I WAS WORKING FLT DATA AT THE TIME OF THE OCCURRENCE. THE SECTOR WAS BUSY. APPLICATION OF GOOD VECTORING OR ALT SEPARATION WOULD HAVE PREVENTED THE OCCURRENCE. THE PLT OF THE SMA Y SAID THE RIGHT TURN PRESCRIBED BY THE CTLR WOULD HAVE PUT HIM RIGHT IN THE SMT X'S PROPELLERS.

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.