Narrative:

Though there were only 4 aircraft on my frequency at the time of the incident, the sector was busy and I had just asked for a handoff to help me out. I was briefing my handoff to let them know what was going on -- 2 towers were waiting for us to call them back for releases on IFR aircraft, we needed to coordinate with 1 adjacent sector for control of an arrival to ful (a C172) and then my handoff coordinated with another adjacent sector to put crj-9 on the lgb localizer to give additional spacing behind a previous cessna lgb arrival. Though the frequency didn't sound busy, the sector was very busy. I had given the C-172 a left turn to 070 degrees toward the ful final approach course. Shortly thereafter, crj checked on at 4000 ft for the lgb localizer (runway 30). I responded 'crj socal approach, roger. Cessna 172, I'm sorry, I'm going to have to turn you back to the right heading 0-9-0.' I missed the complete response which was 'ok 0-9-0 for now, crj.' when I observed the crj turning opposite direction to the final, my handoff and I immediately coordinated with the adjacent sectors and luckily there was no loss of separation. We also were able to resolve the potential conflict of the C-172 and the traffic he was turned to avoid. Both aircraft landed without incident. Had I not 'combined' xmissions, it is probable that the crj would not have responded incorrectly to someone else's control instruction. Had the crj used his call sign in the response instead of just his numbers, it is probable that I would have caught his mistake.

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Original NASA ASRS Text

Title: SCT CTLR DESCRIBES COM ERRORS WHICH COULD HAVE RESULTED IN A LOSS OF SEPARATION.

Narrative: THOUGH THERE WERE ONLY 4 ACFT ON MY FREQ AT THE TIME OF THE INCIDENT, THE SECTOR WAS BUSY AND I HAD JUST ASKED FOR A HDOF TO HELP ME OUT. I WAS BRIEFING MY HDOF TO LET THEM KNOW WHAT WAS GOING ON -- 2 TWRS WERE WAITING FOR US TO CALL THEM BACK FOR RELEASES ON IFR ACFT, WE NEEDED TO COORDINATE WITH 1 ADJACENT SECTOR FOR CTL OF AN ARR TO FUL (A C172) AND THEN MY HDOF COORDINATED WITH ANOTHER ADJACENT SECTOR TO PUT CRJ-9 ON THE LGB LOC TO GIVE ADDITIONAL SPACING BEHIND A PREVIOUS CESSNA LGB ARR. THOUGH THE FREQ DIDN'T SOUND BUSY, THE SECTOR WAS VERY BUSY. I HAD GIVEN THE C-172 A L TURN TO 070 DEGS TOWARD THE FUL FINAL APCH COURSE. SHORTLY THEREAFTER, CRJ CHKED ON AT 4000 FT FOR THE LGB LOC (RWY 30). I RESPONDED 'CRJ SOCAL APCH, ROGER. CESSNA 172, I'M SORRY, I'M GOING TO HAVE TO TURN YOU BACK TO THE RIGHT HDG 0-9-0.' I MISSED THE COMPLETE RESPONSE WHICH WAS 'OK 0-9-0 FOR NOW, CRJ.' WHEN I OBSERVED THE CRJ TURNING OPPOSITE DIRECTION TO THE FINAL, MY HDOF AND I IMMEDIATELY COORDINATED WITH THE ADJACENT SECTORS AND LUCKILY THERE WAS NO LOSS OF SEPARATION. WE ALSO WERE ABLE TO RESOLVE THE POTENTIAL CONFLICT OF THE C-172 AND THE TFC HE WAS TURNED TO AVOID. BOTH ACFT LANDED WITHOUT INCIDENT. HAD I NOT 'COMBINED' XMISSIONS, IT IS PROBABLE THAT THE CRJ WOULD NOT HAVE RESPONDED INCORRECTLY TO SOMEONE ELSE'S CTL INSTRUCTION. HAD THE CRJ USED HIS CALL SIGN IN THE RESPONSE INSTEAD OF JUST HIS NUMBERS, IT IS PROBABLE THAT I WOULD HAVE CAUGHT HIS MISTAKE.

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.