Narrative:

This is being treated as a system error by the FAA, but might have been a pilot deviation. Numerous aircraft were being vectored for arrival sequencing to rdu. The aircraft involved were commuter X and air carrier Y. Based in the projected flight path of both aircraft and the ground speed indicated in the data tags, I felt ample sep would be consistent as the aircraft continued to join the rdu 120 degree right inbound. Therefore, both aircraft were given a descent clearance to 11000'. At the onset of the arrival period for rdu, seymour-johnson approach control requested and was given the echo MOA by the center supervisor in charge of the particular area. It appeared to me that commuter X started an early turn toward the rdu VOR, thus diminishing the expected sep at a given point. X was given an eastbound heading and stopped at 12000'. Air carrier Y was already below X by 100' so his descent was continued to 11000'. The C/a was activated and the closest point was 3.2 mi latitude. A left turn could not be given to X because of the active MOA. Y was below X, so X was stopped at 12000' while Y's descent was continued to 11000'. The hubbing concept that is prevalent in today's aviation society tends to pour a high vol of inbound aircraft into a terminal area in a relatively short period of time and the reverse is true when the departure phase starts. The way our area is structured, the aircraft during the arrival period are constantly being pointed out to adjacent sectors and retained on the original frequency to reduce coordination while trying to sequence the aircraft for the terminal environment. I feel that we need to consider revising sector boundaries, deny use of special use airspace when this traffic surge occurs, consider implementing the use of visibility sep by center controllers to facilitate climb/descent west/O unnecessary restrictions to the user.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN COMMUTER AND ACR. OPERATIONAL ERROR.

Narrative: THIS IS BEING TREATED AS A SYS ERROR BY THE FAA, BUT MIGHT HAVE BEEN A PLTDEV. NUMEROUS ACFT WERE BEING VECTORED FOR ARR SEQUENCING TO RDU. THE ACFT INVOLVED WERE COMMUTER X AND ACR Y. BASED IN THE PROJECTED FLT PATH OF BOTH ACFT AND THE GND SPD INDICATED IN THE DATA TAGS, I FELT AMPLE SEP WOULD BE CONSISTENT AS THE ACFT CONTINUED TO JOIN THE RDU 120 DEG R INBND. THEREFORE, BOTH ACFT WERE GIVEN A DSCNT CLRNC TO 11000'. AT THE ONSET OF THE ARR PERIOD FOR RDU, SEYMOUR-JOHNSON APCH CTL REQUESTED AND WAS GIVEN THE ECHO MOA BY THE CENTER SUPVR IN CHARGE OF THE PARTICULAR AREA. IT APPEARED TO ME THAT COMMUTER X STARTED AN EARLY TURN TOWARD THE RDU VOR, THUS DIMINISHING THE EXPECTED SEP AT A GIVEN POINT. X WAS GIVEN AN EBND HDG AND STOPPED AT 12000'. ACR Y WAS ALREADY BELOW X BY 100' SO HIS DSCNT WAS CONTINUED TO 11000'. THE C/A WAS ACTIVATED AND THE CLOSEST POINT WAS 3.2 MI LAT. A LEFT TURN COULD NOT BE GIVEN TO X BECAUSE OF THE ACTIVE MOA. Y WAS BELOW X, SO X WAS STOPPED AT 12000' WHILE Y'S DSCNT WAS CONTINUED TO 11000'. THE HUBBING CONCEPT THAT IS PREVALENT IN TODAY'S AVIATION SOCIETY TENDS TO POUR A HIGH VOL OF INBND ACFT INTO A TERMINAL AREA IN A RELATIVELY SHORT PERIOD OF TIME AND THE REVERSE IS TRUE WHEN THE DEP PHASE STARTS. THE WAY OUR AREA IS STRUCTURED, THE ACFT DURING THE ARR PERIOD ARE CONSTANTLY BEING POINTED OUT TO ADJACENT SECTORS AND RETAINED ON THE ORIGINAL FREQ TO REDUCE COORD WHILE TRYING TO SEQUENCE THE ACFT FOR THE TERMINAL ENVIRONMENT. I FEEL THAT WE NEED TO CONSIDER REVISING SECTOR BOUNDARIES, DENY USE OF SPECIAL USE AIRSPACE WHEN THIS TFC SURGE OCCURS, CONSIDER IMPLEMENTING THE USE OF VIS SEP BY CENTER CTLRS TO FACILITATE CLB/DSCNT W/O UNNECESSARY RESTRICTIONS TO THE USER.

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.