Narrative:

Air carrier X was on the karlo 2 arrival into phoenix airport with restrictions to cross plsnt intersection at 12000 ft and 250 KTS. Aircraft Y was on a flight from st johns to julian at 16000. I noticed the air carrier X on the arrival was 40 mi northwest of the en route aircraft and had not started their descent. I told the air carrier X on the arrival to start his descent and to expedite through 15000. When the aircraft were 15 mi apart I gave traffic to them. At this time I asked air carrier X on the arrival to say altitude. His reply was through 17500. At this time the aircraft's data block was not displaying any mode C. Also at this time, in my estimation, air carrier X would be below the en route aircraft. When the aircraft were 6 mi apart I asked again 'say altitude.' air carrier X replied 16500. At this time I told air carrier X I needed him through 15000 in 20 seconds. He said he could do it but it would be tight. I further told him to report through 15,000. I put a halo on the aircraft Y so that I would know exactly what 5 mi was. As the halo came up on the scope the descending aircraft reported through 15000. At this time the descending aircraft was on the edge of the halo (5 mi). During this time when the descending aircraft was transmitting his transmissions were broken and unreadable. Also at the time the aircraft were 6 mi apart I turned air carrier X to a heading of 270 and I turned aircraft Y 90 degree to the right. Some of the contributing factors in this event I believe were poor radio communications (static, broken, unreadable transmissions). Also, there were beacon jumps in the phoenix area. No mode C information on aircraft in a rapid descent. Training on the use of the halos, ie, if an aircraft's beacon is on the edge of a halo, do I as a controller still have separation?

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Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACFT Y. SYSTEM ERROR.

Narrative: ACR X WAS ON THE KARLO 2 ARR INTO PHOENIX ARPT WITH RESTRICTIONS TO CROSS PLSNT INTXN AT 12000 FT AND 250 KTS. ACFT Y WAS ON A FLT FROM ST JOHNS TO JULIAN AT 16000. I NOTICED THE ACR X ON THE ARR WAS 40 MI NW OF THE ENRTE ACFT AND HAD NOT STARTED THEIR DSCNT. I TOLD THE ACR X ON THE ARR TO START HIS DSCNT AND TO EXPEDITE THROUGH 15000. WHEN THE ACFT WERE 15 MI APART I GAVE TFC TO THEM. AT THIS TIME I ASKED ACR X ON THE ARR TO SAY ALT. HIS REPLY WAS THROUGH 17500. AT THIS TIME THE ACFT'S DATA BLOCK WAS NOT DISPLAYING ANY MODE C. ALSO AT THIS TIME, IN MY ESTIMATION, ACR X WOULD BE BELOW THE ENRTE ACFT. WHEN THE ACFT WERE 6 MI APART I ASKED AGAIN 'SAY ALT.' ACR X REPLIED 16500. AT THIS TIME I TOLD ACR X I NEEDED HIM THROUGH 15000 IN 20 SECONDS. HE SAID HE COULD DO IT BUT IT WOULD BE TIGHT. I FURTHER TOLD HIM TO REPORT THROUGH 15,000. I PUT A HALO ON THE ACFT Y SO THAT I WOULD KNOW EXACTLY WHAT 5 MI WAS. AS THE HALO CAME UP ON THE SCOPE THE DESCENDING ACFT REPORTED THROUGH 15000. AT THIS TIME THE DESCENDING ACFT WAS ON THE EDGE OF THE HALO (5 MI). DURING THIS TIME WHEN THE DESCENDING ACFT WAS TRANSMITTING HIS TRANSMISSIONS WERE BROKEN AND UNREADABLE. ALSO AT THE TIME THE ACFT WERE 6 MI APART I TURNED ACR X TO A HDG OF 270 AND I TURNED ACFT Y 90 DEG TO THE RIGHT. SOME OF THE CONTRIBUTING FACTORS IN THIS EVENT I BELIEVE WERE POOR RADIO COMS (STATIC, BROKEN, UNREADABLE TRANSMISSIONS). ALSO, THERE WERE BEACON JUMPS IN THE PHOENIX AREA. NO MODE C INFO ON ACFT IN A RAPID DSCNT. TRAINING ON THE USE OF THE HALOS, IE, IF AN ACFT'S BEACON IS ON THE EDGE OF A HALO, DO I AS A CTLR STILL HAVE SEPARATION?

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.