Narrative:

I was working departure 2 and 3 combined with 2 frequencys. Air carrier X and air carrier Y departed dfw on 2 different frequencys. While giving a climb and turn instruction to air carrier X on one frequency, air carrier Y kept reading back the instruction on the other frequency. During this, aircraft Z checked on frequency climbing to 7000 ft. When aircraft Z checked on frequency, air carrier Y was reading back a clearance on the other frequency and I believe air carrier Y blocked aircraft Z's transmission. I don't remember aircraft Z calling me and I just rogered him assuming he was on frequency and climbing to at least 8000 ft. I amended air carrier west's altitude to 7000 ft with the assumption that aircraft Z was climbing above 7000 ft. I turned aircraft Z to 270 degrees and air carrier west to 260 degrees. After working other aircraft and giving a briefing to a departure 2 controller I noted that aircraft Z was level at 7000 ft and I issued air carrier west a clearance to maintain 6000 ft. Air carrier west was at about 5700 ft and went to 6100 ft before going back to 6000 ft. The 2 aircraft were 900 ft apart but they needed to be 1000 ft apart according to the rules. This error was caused by a poor assumption that the other controller climb to the same altitude that I was trained. Another problem with this error is that the altitude that aircraft Z would have been climbing to was from '50 to 100 thousand ft.' there is no set altitude.

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Original NASA ASRS Text

Title: D10 DEP CTLR WORKING 2 DEP POS AND LISTENING ON 2 FREQS HEARS BLOCKED XMISSION, RESPONSE FROM WRONG ACFT, AND ASSUMES WHAT HE CAN'T REMEMBER.

Narrative: I WAS WORKING DEP 2 AND 3 COMBINED WITH 2 FREQS. ACR X AND ACR Y DEPARTED DFW ON 2 DIFFERENT FREQS. WHILE GIVING A CLB AND TURN INSTRUCTION TO ACR X ON ONE FREQ, ACR Y KEPT READING BACK THE INSTRUCTION ON THE OTHER FREQ. DURING THIS, ACFT Z CHKED ON FREQ CLBING TO 7000 FT. WHEN ACFT Z CHKED ON FREQ, ACR Y WAS READING BACK A CLRNC ON THE OTHER FREQ AND I BELIEVE ACR Y BLOCKED ACFT Z'S XMISSION. I DON'T REMEMBER ACFT Z CALLING ME AND I JUST ROGERED HIM ASSUMING HE WAS ON FREQ AND CLBING TO AT LEAST 8000 FT. I AMENDED ACR W'S ALT TO 7000 FT WITH THE ASSUMPTION THAT ACFT Z WAS CLBING ABOVE 7000 FT. I TURNED ACFT Z TO 270 DEGS AND ACR W TO 260 DEGS. AFTER WORKING OTHER ACFT AND GIVING A BRIEFING TO A DEP 2 CTLR I NOTED THAT ACFT Z WAS LEVEL AT 7000 FT AND I ISSUED ACR W A CLRNC TO MAINTAIN 6000 FT. ACR W WAS AT ABOUT 5700 FT AND WENT TO 6100 FT BEFORE GOING BACK TO 6000 FT. THE 2 ACFT WERE 900 FT APART BUT THEY NEEDED TO BE 1000 FT APART ACCORDING TO THE RULES. THIS ERROR WAS CAUSED BY A POOR ASSUMPTION THAT THE OTHER CTLR CLB TO THE SAME ALT THAT I WAS TRAINED. ANOTHER PROB WITH THIS ERROR IS THAT THE ALT THAT ACFT Z WOULD HAVE BEEN CLBING TO WAS FROM '50 TO 100 THOUSAND FT.' THERE IS NO SET ALT.

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.