Narrative:

After an incident involving miscom which I reported 2 days earlier, I am appalled to state that I permitted a takeoff to be initiated without ATC clearance. We were cleared into position on runway 26R. I called for the final items on the before takeoff checklist which were completed as I taxied into position. As I was responding to one of the last items a takeoff clearance was issued. The first officer acknowledged the clearance with a complete readback including runway. I did not hear the flight number when the clearance was issued. I then violated a personal rule of mine which requires both pilots to clearly hear critical xmissions, or a verification from the controller would be required. This I failed to do. I recall thinking that this first officer was one of the best and most trustworthy of any I had ever flown with. His authoritative readback dispelled my unease at accepting such a clearance. At approximately 20 KTS a company flight transmitted that someone else had accepted his takeoff clearance. The tower then told us we were not cleared for takeoff and we rejected the takeoff, coming to a stop about 1000 ft down the runway. We were cleared back into position and departed a few mins later. Later, I asked the first officer just what he heard. He replied that he wasn't sure of the flight number but was counting on the controller's hearback to provide verification of the clearance. We decided that procedure is not reliable, and that direct questions must be employed to provide verification in such situations. Supplemental information from acn 209796: too much in a hurry. Not wanting to be told twice like a boob. Keep the system moving. I assumed the captain had also heard the clearance but this 1 time he violated his own rule of not accepting a takeoff clearance he had not heard himself. We've flown together quite a lot and he made the mistake of trusting me. If I'd been able to hold onto that brief thought that the blocked transmission might pertain to us we could've avoided the mistake. This is an ongoing battle. A brief thought of something amiss is quickly obliterated by the situation or the task at hand. I don't know how to combat this. Poor excuse maybe but I can't help but wonder how I could get a clearance so completely wrong.

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Original NASA ASRS Text

Title: TKOF ABORTED AFTER ACR MLG IS TOLD TO STOP TKOF BY TWR. REPLY TO WRONG CALL SIGN.

Narrative: AFTER AN INCIDENT INVOLVING MISCOM WHICH I RPTED 2 DAYS EARLIER, I AM APPALLED TO STATE THAT I PERMITTED A TKOF TO BE INITIATED WITHOUT ATC CLRNC. WE WERE CLRED INTO POS ON RWY 26R. I CALLED FOR THE FINAL ITEMS ON THE BEFORE TKOF CHKLIST WHICH WERE COMPLETED AS I TAXIED INTO POS. AS I WAS RESPONDING TO ONE OF THE LAST ITEMS A TKOF CLRNC WAS ISSUED. THE FO ACKNOWLEDGED THE CLRNC WITH A COMPLETE READBACK INCLUDING RWY. I DID NOT HEAR THE FLT NUMBER WHEN THE CLRNC WAS ISSUED. I THEN VIOLATED A PERSONAL RULE OF MINE WHICH REQUIRES BOTH PLTS TO CLRLY HEAR CRITICAL XMISSIONS, OR A VERIFICATION FROM THE CTLR WOULD BE REQUIRED. THIS I FAILED TO DO. I RECALL THINKING THAT THIS FO WAS ONE OF THE BEST AND MOST TRUSTWORTHY OF ANY I HAD EVER FLOWN WITH. HIS AUTHORITATIVE READBACK DISPELLED MY UNEASE AT ACCEPTING SUCH A CLRNC. AT APPROX 20 KTS A COMPANY FLT XMITTED THAT SOMEONE ELSE HAD ACCEPTED HIS TKOF CLRNC. THE TWR THEN TOLD US WE WERE NOT CLRED FOR TKOF AND WE REJECTED THE TKOF, COMING TO A STOP ABOUT 1000 FT DOWN THE RWY. WE WERE CLRED BACK INTO POS AND DEPARTED A FEW MINS LATER. LATER, I ASKED THE FO JUST WHAT HE HEARD. HE REPLIED THAT HE WASN'T SURE OF THE FLT NUMBER BUT WAS COUNTING ON THE CTLR'S HEARBACK TO PROVIDE VERIFICATION OF THE CLRNC. WE DECIDED THAT PROC IS NOT RELIABLE, AND THAT DIRECT QUESTIONS MUST BE EMPLOYED TO PROVIDE VERIFICATION IN SUCH SITUATIONS. SUPPLEMENTAL INFORMATION FROM ACN 209796: TOO MUCH IN A HURRY. NOT WANTING TO BE TOLD TWICE LIKE A BOOB. KEEP THE SYS MOVING. I ASSUMED THE CAPT HAD ALSO HEARD THE CLRNC BUT THIS 1 TIME HE VIOLATED HIS OWN RULE OF NOT ACCEPTING A TKOF CLRNC HE HAD NOT HEARD HIMSELF. WE'VE FLOWN TOGETHER QUITE A LOT AND HE MADE THE MISTAKE OF TRUSTING ME. IF I'D BEEN ABLE TO HOLD ONTO THAT BRIEF THOUGHT THAT THE BLOCKED XMISSION MIGHT PERTAIN TO US WE COULD'VE AVOIDED THE MISTAKE. THIS IS AN ONGOING BATTLE. A BRIEF THOUGHT OF SOMETHING AMISS IS QUICKLY OBLITERATED BY THE SITUATION OR THE TASK AT HAND. I DON'T KNOW HOW TO COMBAT THIS. POOR EXCUSE MAYBE BUT I CAN'T HELP BUT WONDER HOW I COULD GET A CLRNC SO COMPLETELY WRONG.

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.