Narrative:

I instructed aircraft X; a bell ranger inbound to cvg; to remain east of the runway 18L centerline. The pilot read back 'remain east of the runway 18 centerline.' I continued to clear aircraft to land and take off from runway 18L. Aircraft X asked if they were cleared into the class B airspace. I issued clearance into the class B and reiterated; what I thought to be; instructions to remain east of runway 18L. I had aircraft Y; a crj; with a flow time to meet at runway 18L. I instructed that aircraft to position and hold on runway 18L. When the preceding arrival cleared the runway; I informed the crj of the jet ranger traffic and that it was remaining east of the runway; then cleared him for takeoff. At that very moment; I observed aircraft X flying across the runway at the T6 intersection en route to the FBO. There was no time to cancel aircraft Y's takeoff clearance. Aircraft X was across the runway and going down taxiway M before aircraft Y began his takeoff roll. I was so shaken by the incident that I informed aircraft X to call the tower and failed to issue a landing clearance of which the pilot landed without. The pilot informed me that they heard 'remain east of runway 18C.' I immediately asked to be relieved from position so I could review the tapes. I had originally issued 'remain east of runway 18L' then when the pilot asked for class B clearance; I mistakenly reclred the pilot to remain east of runway 18C and missed the readback of runway 18C.

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Original NASA ASRS Text

Title: CVG CTLR DESCRIBED POTENTIAL CONFLICT WITH INBOUND HELI AND DEP ACFT ON RWY 18L/18C OPERATION; LISTING FAILED HEARBACK AS CAUSAL FACTOR.

Narrative: I INSTRUCTED ACFT X; A BELL RANGER INBOUND TO CVG; TO REMAIN E OF THE RWY 18L CTRLINE. THE PLT READ BACK 'REMAIN E OF THE RWY 18 CTRLINE.' I CONTINUED TO CLR ACFT TO LAND AND TAKE OFF FROM RWY 18L. ACFT X ASKED IF THEY WERE CLRED INTO THE CLASS B AIRSPACE. I ISSUED CLRNC INTO THE CLASS B AND REITERATED; WHAT I THOUGHT TO BE; INSTRUCTIONS TO REMAIN E OF RWY 18L. I HAD ACFT Y; A CRJ; WITH A FLOW TIME TO MEET AT RWY 18L. I INSTRUCTED THAT ACFT TO POS AND HOLD ON RWY 18L. WHEN THE PRECEDING ARR CLRED THE RWY; I INFORMED THE CRJ OF THE JET RANGER TFC AND THAT IT WAS REMAINING E OF THE RWY; THEN CLRED HIM FOR TKOF. AT THAT VERY MOMENT; I OBSERVED ACFT X FLYING ACROSS THE RWY AT THE T6 INTXN ENRTE TO THE FBO. THERE WAS NO TIME TO CANCEL ACFT Y'S TKOF CLRNC. ACFT X WAS ACROSS THE RWY AND GOING DOWN TXWY M BEFORE ACFT Y BEGAN HIS TKOF ROLL. I WAS SO SHAKEN BY THE INCIDENT THAT I INFORMED ACFT X TO CALL THE TWR AND FAILED TO ISSUE A LNDG CLRNC OF WHICH THE PLT LANDED WITHOUT. THE PLT INFORMED ME THAT THEY HEARD 'REMAIN E OF RWY 18C.' I IMMEDIATELY ASKED TO BE RELIEVED FROM POS SO I COULD REVIEW THE TAPES. I HAD ORIGINALLY ISSUED 'REMAIN E OF RWY 18L' THEN WHEN THE PLT ASKED FOR CLASS B CLRNC; I MISTAKENLY RECLRED THE PLT TO REMAIN E OF RWY 18C AND MISSED THE READBACK OF RWY 18C.

Data retrieved from NASA's ASRS site as of May 2009 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.