Sct controller described a loss of separation event between a san air carrier arrival and a VFR airc...

Attributes
ACN	883539
Time
Date	201004
Local Time Of Day	1201-1800
Place
Locale Reference	SAN.Airport
State Reference	CA
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Beechcraft Twin Turboprop or Jet Undifferentiated or Other Model
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Person 2
Function	Pilot Flying First Officer
Experience	Flight Crew Last 90 Days 135 Flight Crew Type 6500
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Published Material / Policy

Narrative:

I was working east radar and had several san arrivals; was coordinating 2 nzy arrivals; had a king air working near the north part of my sector; and an IFR pickup calling me for myf. I descended air carrier X to 4000 on a downwind heading. I issued a code to and identified a C172 landing myf and issued a class B clearance. I turned air carrier X base and noticed the king air less than a mile ahead issued traffic and told air carrier X to expedite decent. Air carrier X reported a near midair collision with the king air and I notified the supervisor. It was also a loss of separation since both were in the class B unless somehow their courses were diverging. Get a better track for the king air's operation to keep it out of high traffic areas. Get projected track lines so the controller can see turns quicker. Have an assist in place before traffic gets busy instead of trying to do something after it's already there.

Original NASA ASRS Text

Title: SCT Controller described a loss of separation event between a SAN air carrier arrival and a VFR aircraft maneuvering; the reporter noted availability of projected track lines on the display and staffing improvements may have prevented the error.

Narrative: I was working East RADAR and had several SAN arrivals; was coordinating 2 NZY arrivals; had a King Air working near the north part of my sector; and an IFR pickup calling me for MYF. I descended Air Carrier X to 4000 on a downwind heading. I issued a code to and identified a C172 landing MYF and issued a Class B clearance. I turned Air Carrier X base and noticed the King Air less than a mile ahead issued traffic and told Air Carrier X to expedite decent. Air Carrier X reported a NMAC with the King Air and I notified the Supervisor. It was also a loss of separation since both were in the Class B unless somehow their courses were diverging. Get a better track for the King Air's operation to keep it out of high traffic areas. Get projected track lines so the Controller can see turns quicker. Have an assist in place before traffic gets busy instead of trying to do something after it's already there.

Data retrieved from NASA's ASRS site as of April 2012 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.

Sct controller described a loss of separation event between a san air carrier arrival and a VFR aircraft maneuvering; the reporter noted availability of projected track lines on the display and staffing improvements may have prevented the error.