Narrative:

I was controller in charge of the ozark area in ZKC. Radar controller, a controller under my supervision, had a missed readback error that resulted in a loss of separation. The closest point was 0.7 lateral and 0 ft altitude. Supplemental information from acn 212922: cpr X was at 10000 ft requesting 14000 ft. I then issued 14000 and then later attempted to reclr him to 12000 for air carrier Y at 13000 ft level. When I issued the clearance to 12000, another aircraft was transmitting at the same time and after I unkeyed, I heard the end of his transmission and thought it was the readback from cpr X. Supplemental information from acn 213632: cpr X was cleared to climb from 10000 to 14000 by ZKC. As we passed 13000, we passed within about 1/8 mi of an air carrier Y who was nnebound, talking to same controller. Controller: 'cpr X you we told to stop at 12000!' cpr X: 'negative, sir.' controller 'yes, you were! You acknowledged the transmission!' cpr Y 'negative, sir.' we later called ZKC, after they had replayed the tape. The controller's transmission, telling us to stop the climb had been blocked (or so we were told. We never heard it or acknowledged).

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Original NASA ASRS Text

Title: CPR X CLB THROUGH OCCUPIED ALT HAD LTSS FROM ACR Y. SYS ERROR. POTENTIAL CONFLICT.

Narrative: I WAS CTLR IN CHARGE OF THE OZARK AREA IN ZKC. RADAR CTLR, A CTLR UNDER MY SUPERVISION, HAD A MISSED READBACK ERROR THAT RESULTED IN A LOSS OF SEPARATION. THE CLOSEST POINT WAS 0.7 LATERAL AND 0 FT ALT. SUPPLEMENTAL INFO FROM ACN 212922: CPR X WAS AT 10000 FT REQUESTING 14000 FT. I THEN ISSUED 14000 AND THEN LATER ATTEMPTED TO RECLR HIM TO 12000 FOR ACR Y AT 13000 FT LEVEL. WHEN I ISSUED THE CLRNC TO 12000, ANOTHER ACFT WAS XMITTING AT THE SAME TIME AND AFTER I UNKEYED, I HEARD THE END OF HIS XMISSION AND THOUGHT IT WAS THE READBACK FROM CPR X. SUPPLEMENTAL INFO FROM ACN 213632: CPR X WAS CLRED TO CLB FROM 10000 TO 14000 BY ZKC. AS WE PASSED 13000, WE PASSED WITHIN ABOUT 1/8 MI OF AN ACR Y WHO WAS NNEBOUND, TALKING TO SAME CTLR. CTLR: 'CPR X YOU WE TOLD TO STOP AT 12000!' CPR X: 'NEGATIVE, SIR.' CTLR 'YES, YOU WERE! YOU ACKNOWLEDGED THE XMISSION!' CPR Y 'NEGATIVE, SIR.' WE LATER CALLED ZKC, AFTER THEY HAD REPLAYED THE TAPE. THE CTLR'S XMISSION, TELLING US TO STOP THE CLB HAD BEEN BLOCKED (OR SO WE WERE TOLD. WE NEVER HEARD IT OR ACKNOWLEDGED).

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.