Narrative:

Air carrier X on downwind vector at 6000'. Cga Y departed heading 270 degrees, climbing to 5000', and cga Z departed 270 degrees, climbing to 5000'. Cga Y given 290 degrees direct mie. When he was clear of downwind traffic, given climb to 8000'. Cga Z given 320 degree heading. Cga Z started climbing above 5000' and controller told him his assigned altitude was 5000'. He said he thought the 8000' was for him. Traffic was issued at 10 O'clock and 2 mi, an medium large transport. After reviewing tape, cga Z had responded instead of cga Y. Neither cga Z or cga Y responded at any time using prefix. This may have helped controller catch error. Air carrier X said he saw cga Z, but had to make a violent turn to avoid traffic. Supplemental information from acn 128075: we were assigned and level at 6000'. Approach called traffic at 2 O'clock at 5000'. When I picked him up visually, he appeared to be above us, not below. Shortly thereafter I heard the controller advise the small transport traffic that he had been assigned 5000'. The small transport stated that he thought he had been given 8000' and was descending back to 5000'. At that point, he was slightly above us and headed right for us, from approximately our 1 O'clock position, 1 1/2-2 mi. He never changed course and I was forced to make a 45 degree right bank turn and lose approximately 400' to avoid hitting the small transport as he crossed just in front of us. A follow-up phone call to day approach revealed that controller training was in progress. The small transport pilot had apparently taken a clearance meant for another aircraft, and read back the clearance with is call sign. The controller, however, both missed his readback and didn't notice anything wrong until the small transport was well above his assigned altitude. Apparently this was another case of a combination of frequency congestion, very busy controllers, a training situation and a simple but very dangerous mistake.

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Original NASA ASRS Text

Title: SMT CLIMBED ABOVE ASSIGNED ALT AND CONFLICTED WITH AN ACR.

Narrative: ACR X ON DOWNWIND VECTOR AT 6000'. CGA Y DEPARTED HDG 270 DEGS, CLBING TO 5000', AND CGA Z DEPARTED 270 DEGS, CLBING TO 5000'. CGA Y GIVEN 290 DEGS DIRECT MIE. WHEN HE WAS CLR OF DOWNWIND TFC, GIVEN CLB TO 8000'. CGA Z GIVEN 320 DEG HDG. CGA Z STARTED CLBING ABOVE 5000' AND CTLR TOLD HIM HIS ASSIGNED ALT WAS 5000'. HE SAID HE THOUGHT THE 8000' WAS FOR HIM. TFC WAS ISSUED AT 10 O'CLOCK AND 2 MI, AN MLG. AFTER REVIEWING TAPE, CGA Z HAD RESPONDED INSTEAD OF CGA Y. NEITHER CGA Z OR CGA Y RESPONDED AT ANY TIME USING PREFIX. THIS MAY HAVE HELPED CTLR CATCH ERROR. ACR X SAID HE SAW CGA Z, BUT HAD TO MAKE A VIOLENT TURN TO AVOID TFC. SUPPLEMENTAL INFO FROM ACN 128075: WE WERE ASSIGNED AND LEVEL AT 6000'. APCH CALLED TFC AT 2 O'CLOCK AT 5000'. WHEN I PICKED HIM UP VISUALLY, HE APPEARED TO BE ABOVE US, NOT BELOW. SHORTLY THEREAFTER I HEARD THE CTLR ADVISE THE SMT TFC THAT HE HAD BEEN ASSIGNED 5000'. THE SMT STATED THAT HE THOUGHT HE HAD BEEN GIVEN 8000' AND WAS DSNDING BACK TO 5000'. AT THAT POINT, HE WAS SLIGHTLY ABOVE US AND HEADED RIGHT FOR US, FROM APPROX OUR 1 O'CLOCK POS, 1 1/2-2 MI. HE NEVER CHANGED COURSE AND I WAS FORCED TO MAKE A 45 DEG RIGHT BANK TURN AND LOSE APPROX 400' TO AVOID HITTING THE SMT AS HE CROSSED JUST IN FRONT OF US. A FOLLOW-UP PHONE CALL TO DAY APCH REVEALED THAT CTLR TRNING WAS IN PROGRESS. THE SMT PLT HAD APPARENTLY TAKEN A CLRNC MEANT FOR ANOTHER ACFT, AND READ BACK THE CLRNC WITH IS CALL SIGN. THE CTLR, HOWEVER, BOTH MISSED HIS READBACK AND DIDN'T NOTICE ANYTHING WRONG UNTIL THE SMT WAS WELL ABOVE HIS ASSIGNED ALT. APPARENTLY THIS WAS ANOTHER CASE OF A COMBINATION OF FREQ CONGESTION, VERY BUSY CTLRS, A TRNING SITUATION AND A SIMPLE BUT VERY DANGEROUS MISTAKE.

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.