Narrative:

The sector is primarily an arrival and departure sector and was staffed by 2 fpl controllers. At the time of the incident, there were approximately 25 aircraft and the majority of the arrs were being blended into one stream from 2 streams. The traffic complexity that day was higher than normal due to the number of conflictions that needed to be resolved with en route and arrival aircraft. The departure aircraft cross the paths of the arrival aircraft and need to be stopped at an interim altitude below the arrs and then the arrs are laddered down. The complexity of this particular sector would be greatly reduced if the departures were routed out a separate departure corridor away from my arrs. The 2 aircraft involved were 10 mi in trail, both were descended to FL280 and reduced to 250 KIAS. Aircraft X was vectored north on a 320 heading. Aircraft number Y was vectored about 3 min later north a 330 heading. Both aircraft were on these headings to be blended with another stream coming from the east. Because aircraft Y was vectored later than aircraft X, his position was west of aircraft X, although he was then about 8 mi in trail. Aircraft X was turned left to ffu, the arrival fix. One min later aircraft X was asked to verify that he was turning direct ffu. He acknowledged he was. At that time aircraft Y was turned left to a heading of 220. Aircraft Y caught aircraft X from behind and the conflict alert went off. Aircraft Y was given a descent to FL270 immediately and said he had the other aircraft in sight and complied with the descent clearance. One of the things that should have been done to prevent this from happening was to use altitude separation until longitudinal separation is established.

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Original NASA ASRS Text

Title: ACR BEING SEQUENCED, OVERTOOK TRAFFIC HE WAS FOLLOWING RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: THE SECTOR IS PRIMARILY AN ARR AND DEP SECTOR AND WAS STAFFED BY 2 FPL CTLRS. AT THE TIME OF THE INCIDENT, THERE WERE APPROX 25 ACFT AND THE MAJORITY OF THE ARRS WERE BEING BLENDED INTO ONE STREAM FROM 2 STREAMS. THE TFC COMPLEXITY THAT DAY WAS HIGHER THAN NORMAL DUE TO THE NUMBER OF CONFLICTIONS THAT NEEDED TO BE RESOLVED WITH ENRTE AND ARR ACFT. THE DEP ACFT CROSS THE PATHS OF THE ARR ACFT AND NEED TO BE STOPPED AT AN INTERIM ALT BELOW THE ARRS AND THEN THE ARRS ARE LADDERED DOWN. THE COMPLEXITY OF THIS PARTICULAR SECTOR WOULD BE GREATLY REDUCED IF THE DEPS WERE ROUTED OUT A SEPARATE DEP CORRIDOR AWAY FROM MY ARRS. THE 2 ACFT INVOLVED WERE 10 MI IN TRAIL, BOTH WERE DESCENDED TO FL280 AND REDUCED TO 250 KIAS. ACFT X WAS VECTORED N ON A 320 HDG. ACFT NUMBER Y WAS VECTORED ABOUT 3 MIN LATER N A 330 HDG. BOTH ACFT WERE ON THESE HDGS TO BE BLENDED WITH ANOTHER STREAM COMING FROM THE E. BECAUSE ACFT Y WAS VECTORED LATER THAN ACFT X, HIS POSITION WAS W OF ACFT X, ALTHOUGH HE WAS THEN ABOUT 8 MI IN TRAIL. ACFT X WAS TURNED LEFT TO FFU, THE ARR FIX. ONE MIN LATER ACFT X WAS ASKED TO VERIFY THAT HE WAS TURNING DIRECT FFU. HE ACKNOWLEDGED HE WAS. AT THAT TIME ACFT Y WAS TURNED LEFT TO A HDG OF 220. ACFT Y CAUGHT ACFT X FROM BEHIND AND THE CONFLICT ALERT WENT OFF. ACFT Y WAS GIVEN A DSCNT TO FL270 IMMEDIATELY AND SAID HE HAD THE OTHER ACFT IN SIGHT AND COMPLIED WITH THE DSCNT CLRNC. ONE OF THE THINGS THAT SHOULD HAVE BEEN DONE TO PREVENT THIS FROM HAPPENING WAS TO USE ALT SEPARATION UNTIL LONGITUDINAL SEPARATION IS ESTABLISHED.

Data retrieved from NASA's ASRS site as of August 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.