Narrative:

We were given a turn from 180 to 120 degree while in a descent to 5000'. The captain noticed an aircraft climbing at our 11 O'clock position and approximately 1 mi. He initiated a climb to avoid the aircraft. Our altitude was 6100' when we crossed over the top of the other aircraft. I immediately asked the controller why he didn't report the traffic to us. The controller responded, telling us there was no target on the screen. A newer more advanced radar system in the los angeles basin is needed and would prevent a recurrence from happening.

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Original NASA ASRS Text

Title: CLOSE PROX COMMUTER LTT-UNK 3 NM SOUTH OF LGB WORKING SNA.

Narrative: WE WERE GIVEN A TURN FROM 180 TO 120 DEG WHILE IN A DESCENT TO 5000'. THE CAPT NOTICED AN ACFT CLIMBING AT OUR 11 O'CLOCK POSITION AND APPROX 1 MI. HE INITIATED A CLIMB TO AVOID THE ACFT. OUR ALT WAS 6100' WHEN WE CROSSED OVER THE TOP OF THE OTHER ACFT. I IMMEDIATELY ASKED THE CTLR WHY HE DIDN'T REPORT THE TFC TO US. THE CTLR RESPONDED, TELLING US THERE WAS NO TARGET ON THE SCREEN. A NEWER MORE ADVANCED RADAR SYSTEM IN THE LOS ANGELES BASIN IS NEEDED AND WOULD PREVENT A RECURRENCE FROM HAPPENING.

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.