Narrative:

Immediately after being cleared to position and hold runway 4, I asked the first officer to relay to tower the presence of FOD (a vaseline jar) on taxiway, which he did. Immediately after he did, tower gave us a new departure frequency and told us to fly runway heading. Somehow I concluded we were cleared for takeoff and advanced power. At about 50 KTS, tower started to call us, but stopped abruptly. After takeoff the first officer expressed concern about whether we were cleared for takeoff. I told him to ask tower. He did. Tower said we weren't, but that they were about to clear us when they saw us rolling and that they stopped their transmission. I think the unusual transmission re: FOD contributed to my mistake, but does not excuse it. What really bothered me was that the first officer was concerned at the outset whether we were cleared for takeoff. I explained to him that takeoff clrncs, landing clrncs, heading and altitude changes are all examples of surveys that need 100% understanding in the cockpit. If he is not sure of the clearance, we do not go until we both are. Anyone can make a mistake, but for one of the crew not to mention it when he's not sure does nothing for aviation discipline and safety. Clearly, that mistake could have been prevented. Fatigue was not a factor--it was our first flight of the day after very restful over night in el paso.

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Original NASA ASRS Text

Title: ACR MLG UNAUTH TKOF AT ELP.

Narrative: IMMEDIATELY AFTER BEING CLRED TO POS AND HOLD RWY 4, I ASKED THE F/O TO RELAY TO TWR THE PRESENCE OF FOD (A VASELINE JAR) ON TXWY, WHICH HE DID. IMMEDIATELY AFTER HE DID, TWR GAVE US A NEW DEP FREQ AND TOLD US TO FLY RWY HDG. SOMEHOW I CONCLUDED WE WERE CLRED FOR TKOF AND ADVANCED PWR. AT ABOUT 50 KTS, TWR STARTED TO CALL US, BUT STOPPED ABRUPTLY. AFTER TKOF THE F/O EXPRESSED CONCERN ABOUT WHETHER WE WERE CLRED FOR TKOF. I TOLD HIM TO ASK TWR. HE DID. TWR SAID WE WEREN'T, BUT THAT THEY WERE ABOUT TO CLR US WHEN THEY SAW US ROLLING AND THAT THEY STOPPED THEIR XMISSION. I THINK THE UNUSUAL XMISSION RE: FOD CONTRIBUTED TO MY MISTAKE, BUT DOES NOT EXCUSE IT. WHAT REALLY BOTHERED ME WAS THAT THE F/O WAS CONCERNED AT THE OUTSET WHETHER WE WERE CLRED FOR TKOF. I EXPLAINED TO HIM THAT TKOF CLRNCS, LNDG CLRNCS, HDG AND ALT CHANGES ARE ALL EXAMPLES OF SURVEYS THAT NEED 100% UNDERSTANDING IN THE COCKPIT. IF HE IS NOT SURE OF THE CLRNC, WE DO NOT GO UNTIL WE BOTH ARE. ANYONE CAN MAKE A MISTAKE, BUT FOR ONE OF THE CREW NOT TO MENTION IT WHEN HE'S NOT SURE DOES NOTHING FOR AVIATION DISCIPLINE AND SAFETY. CLEARLY, THAT MISTAKE COULD HAVE BEEN PREVENTED. FATIGUE WAS NOT A FACTOR--IT WAS OUR FIRST FLT OF THE DAY AFTER VERY RESTFUL OVER NIGHT IN EL PASO.

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.