Narrative:

We were taxiing for takeoff on the runway 27L parallel taxiway about 150-200 yds from the approach end. The tower asked if we were ready for an immediate takeoff as he had a widebody transport on 5 mi final. I answered 'XXXX ready'. We were cleared for takeoff, to fly a 290 degree heading. The copilot acknowledged 'air carrier X cleared for takeoff on 27L'. At this same time the tower cleared a small aircraft for takeoff from a 27L intersection. I did not think this unusual as we were still a ways from the approach end and he should be well on his way by the time we started our takeoff roll. As we started our takeoff roll, (copilot was flying), I saw the lights of the other aircraft. I thought he would be lifting off shortly. As we passed 80 KTS, I asked the tower if the small aircraft was accelerating normally. At this time the tower said 'air carrier X, abort your takeoff', which we did. We taxied off the runway, taxied to the approach and shortly made another takeoff. Two days later we were told that we had taken the small aircraft's clearance for takeoff. Our response was on the tower tapes. Evidently two aircraft answered the clearance for takeoff and neither the tower nor aircraft were aware of it. I believe I should have answered 'air carrier X' is ready when asked! That might have alerted the tower. Supplemental information from acn 121652: as the first officer, I was handling the radios and I looked at the captain to see if he was ready. He responded himself with 'XXXX roger'. We were cleared for takeoff and the widebody transport was on a 5 mi final. I responded to the takeoff clearance with full call sign, cleared for takeoff and the specific runway. I told the captain I didn't think things were looking good, referring to our potential overtake of the small aircraft because he hadn't made a turn from runway heading as we thought tower had assigned him. At approximately 90 KTS the captain aborted and the widebody transport had to go around because we were still on the runway.

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Original NASA ASRS Text

Title: ACR BEGAN TKOF ROLL WITHOUT CLRNC AND CONFLICTED WITH A LNDG WDB.

Narrative: WE WERE TAXIING FOR TKOF ON THE RWY 27L PARALLEL TXWY ABOUT 150-200 YDS FROM THE APCH END. THE TWR ASKED IF WE WERE READY FOR AN IMMEDIATE TKOF AS HE HAD A WDB ON 5 MI FINAL. I ANSWERED 'XXXX READY'. WE WERE CLRED FOR TKOF, TO FLY A 290 DEG HDG. THE COPLT ACKNOWLEDGED 'ACR X CLRED FOR TKOF ON 27L'. AT THIS SAME TIME THE TWR CLRED A SMALL ACFT FOR TKOF FROM A 27L INTXN. I DID NOT THINK THIS UNUSUAL AS WE WERE STILL A WAYS FROM THE APCH END AND HE SHOULD BE WELL ON HIS WAY BY THE TIME WE STARTED OUR TKOF ROLL. AS WE STARTED OUR TKOF ROLL, (COPLT WAS FLYING), I SAW THE LIGHTS OF THE OTHER ACFT. I THOUGHT HE WOULD BE LIFTING OFF SHORTLY. AS WE PASSED 80 KTS, I ASKED THE TWR IF THE SMALL ACFT WAS ACCELERATING NORMALLY. AT THIS TIME THE TWR SAID 'ACR X, ABORT YOUR TKOF', WHICH WE DID. WE TAXIED OFF THE RWY, TAXIED TO THE APCH AND SHORTLY MADE ANOTHER TKOF. TWO DAYS LATER WE WERE TOLD THAT WE HAD TAKEN THE SMALL ACFT'S CLRNC FOR TKOF. OUR RESPONSE WAS ON THE TWR TAPES. EVIDENTLY TWO ACFT ANSWERED THE CLRNC FOR TKOF AND NEITHER THE TWR NOR ACFT WERE AWARE OF IT. I BELIEVE I SHOULD HAVE ANSWERED 'ACR X' IS READY WHEN ASKED! THAT MIGHT HAVE ALERTED THE TWR. SUPPLEMENTAL INFORMATION FROM ACN 121652: AS THE F/O, I WAS HANDLING THE RADIOS AND I LOOKED AT THE CAPT TO SEE IF HE WAS READY. HE RESPONDED HIMSELF WITH 'XXXX ROGER'. WE WERE CLRED FOR TKOF AND THE WDB WAS ON A 5 MI FINAL. I RESPONDED TO THE TKOF CLRNC WITH FULL CALL SIGN, CLRED FOR TKOF AND THE SPECIFIC RWY. I TOLD THE CAPT I DIDN'T THINK THINGS WERE LOOKING GOOD, REFERRING TO OUR POTENTIAL OVERTAKE OF THE SMALL ACFT BECAUSE HE HADN'T MADE A TURN FROM RWY HDG AS WE THOUGHT TWR HAD ASSIGNED HIM. AT APPROX 90 KTS THE CAPT ABORTED AND THE WDB HAD TO GO AROUND BECAUSE WE WERE STILL ON THE RWY.

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.