Narrative:

After we arrived at the runway we advised tower that we were ready to depart from intersection W-8. I then heard tower reply 'air carrier X runway 1L cleared for takeoff'. I taxied onto the runway, applied power, and departed. A short time prior to our takeoff clearance I heard tower clear an small transport for takeoff from runway 1R. As we were climbing thru 1200' MSL I heard the tower issue a left turn to the small transport and point us out as traffic. The small transport was now flying directly toward us in a climb. Unsure if the small transport saw our aircraft I began a descent to ensure adequate separation. Just as I was about to express my displeasure with the controller for turning the small transport toward us, the controller mentioned that he had not cleared us for takeoff, only into position and hold. I disagreed. He said 'no harm done' and switched us to departure. I was certain we were cleared for takeoff. But all of a sudden I was immensely unsure and still am. My first officer said he couldn't believe that we both could miss that. I, by habit and discipline, am very thorough about reading back clrncs, and I'm sure I read back what I heard. I fly frequently in and out of iad and the procedures are hardly ever done differently, it's always the same. Surely it is necessary to listen to all instructions and take none for granted. 'No harm done'? Fortunately, not this time. Supplemental information from acn 138188: we departed without a takeoff clearance. Apparently we were given a clearance of 'position and hold', and the captain rolled out on the runway and kept going. Neither the captain nor myself caught the situation. At about 1000' the tower said 'I gave you only a clearance for 'position and hold', that's ok, no problem, contact departure.' it seems we were both relying on each other and busy beginning out next task and assumed we were clear to go.

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Original NASA ASRS Text

Title: ACFT DEPARTED WITHOUT TKOF CLRNC.

Narrative: AFTER WE ARRIVED AT THE RWY WE ADVISED TWR THAT WE WERE READY TO DEPART FROM INTXN W-8. I THEN HEARD TWR REPLY 'ACR X RWY 1L CLRED FOR TKOF'. I TAXIED ONTO THE RWY, APPLIED POWER, AND DEPARTED. A SHORT TIME PRIOR TO OUR TKOF CLRNC I HEARD TWR CLEAR AN SMT FOR TKOF FROM RWY 1R. AS WE WERE CLIMBING THRU 1200' MSL I HEARD THE TWR ISSUE A LEFT TURN TO THE SMT AND POINT US OUT AS TFC. THE SMT WAS NOW FLYING DIRECTLY TOWARD US IN A CLIMB. UNSURE IF THE SMT SAW OUR ACFT I BEGAN A DSCNT TO ENSURE ADEQUATE SEPARATION. JUST AS I WAS ABOUT TO EXPRESS MY DISPLEASURE WITH THE CTLR FOR TURNING THE SMT TOWARD US, THE CTLR MENTIONED THAT HE HAD NOT CLRED US FOR TKOF, ONLY INTO POSITION AND HOLD. I DISAGREED. HE SAID 'NO HARM DONE' AND SWITCHED US TO DEP. I WAS CERTAIN WE WERE CLRED FOR TKOF. BUT ALL OF A SUDDEN I WAS IMMENSELY UNSURE AND STILL AM. MY F/O SAID HE COULDN'T BELIEVE THAT WE BOTH COULD MISS THAT. I, BY HABIT AND DISCIPLINE, AM VERY THOROUGH ABOUT READING BACK CLRNCS, AND I'M SURE I READ BACK WHAT I HEARD. I FLY FREQUENTLY IN AND OUT OF IAD AND THE PROCS ARE HARDLY EVER DONE DIFFERENTLY, IT'S ALWAYS THE SAME. SURELY IT IS NECESSARY TO LISTEN TO ALL INSTRUCTIONS AND TAKE NONE FOR GRANTED. 'NO HARM DONE'? FORTUNATELY, NOT THIS TIME. SUPPLEMENTAL INFORMATION FROM ACN 138188: WE DEPARTED WITHOUT A TKOF CLRNC. APPARENTLY WE WERE GIVEN A CLRNC OF 'POSITION AND HOLD', AND THE CAPT ROLLED OUT ON THE RWY AND KEPT GOING. NEITHER THE CAPT NOR MYSELF CAUGHT THE SITUATION. AT ABOUT 1000' THE TWR SAID 'I GAVE YOU ONLY A CLRNC FOR 'POSITION AND HOLD', THAT'S OK, NO PROBLEM, CONTACT DEP.' IT SEEMS WE WERE BOTH RELYING ON EACH OTHER AND BUSY BEGINNING OUT NEXT TASK AND ASSUMED WE WERE CLEAR TO GO.

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.