Narrative:

Air carrier X was cleared to depart runway 35, turn right to 060 degree heading, maintain 5000'. He rogered clearance, but did not repeat runway or heading. I did not catch the readback or assumed that I heard it verbatim (mistake #1). At the time aircraft Y was on an ILS 35 approach to report OM inbound (3 min departure rule). Aircraft Y reported OM. Aircraft Y issued left turn heading 180 degrees, maintain 3000'. Air carrier X acknowledged and reported off 35 seconds later, turning left out of 3500'. I asked air carrier X again direction of turn. Air carrier X said left. I then reissued right heading 060 degrees. Air carrier X said he thought I said left turn on departure heading 160 degrees (mistake #2). Both mistakes are what we want to hear, not what is said. Situation could have resulted in a mid-air collision, if not for having aircraft Y established southbound before air carrier X departed. I was at fault for not listening for the readback or thinking I heard complete readback. Pilot of air carrier X was at fault for not verifying the heading or giving a complete readback. Moral of story: when in doubt, ask again, and give complete readbacks. For both myself and pilot of air carrier X, we were assuming, and that is not conducive to a safe ATC system.

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Original NASA ASRS Text

Title: ACR X FAILED TO COMPLY WITH ATC CLRNC. OPERATIONAL DEVIATION. ARTCC RADAR CTLR FAILED TO HEAR ACR X ACKNOWLEDGE A CLRNC FOR ACFT Y.

Narrative: ACR X WAS CLRED TO DEPART RWY 35, TURN RIGHT TO 060 DEG HDG, MAINTAIN 5000'. HE ROGERED CLRNC, BUT DID NOT REPEAT RWY OR HDG. I DID NOT CATCH THE READBACK OR ASSUMED THAT I HEARD IT VERBATIM (MISTAKE #1). AT THE TIME ACFT Y WAS ON AN ILS 35 APCH TO RPT OM INBND (3 MIN DEP RULE). ACFT Y RPTED OM. ACFT Y ISSUED LEFT TURN HDG 180 DEGS, MAINTAIN 3000'. ACR X ACKNOWLEDGED AND RPTED OFF 35 SECS LATER, TURNING LEFT OUT OF 3500'. I ASKED ACR X AGAIN DIRECTION OF TURN. ACR X SAID LEFT. I THEN REISSUED RIGHT HDG 060 DEGS. ACR X SAID HE THOUGHT I SAID LEFT TURN ON DEP HDG 160 DEGS (MISTAKE #2). BOTH MISTAKES ARE WHAT WE WANT TO HEAR, NOT WHAT IS SAID. SITUATION COULD HAVE RESULTED IN A MID-AIR COLLISION, IF NOT FOR HAVING ACFT Y ESTABLISHED SBND BEFORE ACR X DEPARTED. I WAS AT FAULT FOR NOT LISTENING FOR THE READBACK OR THINKING I HEARD COMPLETE READBACK. PLT OF ACR X WAS AT FAULT FOR NOT VERIFYING THE HDG OR GIVING A COMPLETE READBACK. MORAL OF STORY: WHEN IN DOUBT, ASK AGAIN, AND GIVE COMPLETE READBACKS. FOR BOTH MYSELF AND PLT OF ACR X, WE WERE ASSUMING, AND THAT IS NOT CONDUCIVE TO A SAFE ATC SYS.

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.