Narrative:

I was receiving dual instruction in a small aircraft sel, for an upcoming CFI check ride. We received taxi clearance 'to runway 19R, hold short of runway 19L.' as we taxied northbound on alpha on the east side of the field, my instructor and I were discussing the lesson for the day. We turned onto taxiway C which parallels alpha. When we were approximately 800 ft from the approach end of runways 19, we were advised to contact tower. We acknowledged, and continued taxiing. I was going through an explanation of the takeoff that my instructor had given me. When I had finished, we were just pulling into a hold short position. We then switched to tower frequency. I then heard the controller say what I perceived as our aircraft number and the clearance 'cleared for takeoff, runway 19L, fly runway heading, I'll call your right turn.' I then repeated back our call sign and 'cleared for takeoff, on the left' as we rolled onto the runway and added power. When we were approximately 500 ft AGL on the upwind, we were advised by tower that she didn't release us for takeoff. She then instructed us to contact radar advisories, which we did. The flight continued uneventful till termination. In retrospect, I think the problem could possibly have been avoided by tuning in tower sooner, or by not being handed off prematurely. Secondly, I should have insisted on an answer to my query 'cleared for takeoff on the left.' it is unclr why the controller used our call sign on call up, which I believe she did. Attention to detail and more care in ascertaining clrncs could have helped as well.

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Original NASA ASRS Text

Title: INSTRUCTOR TRAINEE INADVERTENTLY MADE AN UNAUTH TKOF.

Narrative: I WAS RECEIVING DUAL INSTRUCTION IN A SMA SEL, FOR AN UPCOMING CFI CHECK RIDE. WE RECEIVED TAXI CLRNC 'TO RWY 19R, HOLD SHORT OF RWY 19L.' AS WE TAXIED NBOUND ON ALPHA ON THE E SIDE OF THE FIELD, MY INSTRUCTOR AND I WERE DISCUSSING THE LESSON FOR THE DAY. WE TURNED ONTO TXWY C WHICH PARALLELS ALPHA. WHEN WE WERE APPROX 800 FT FROM THE APCH END OF RWYS 19, WE WERE ADVISED TO CONTACT TWR. WE ACKNOWLEDGED, AND CONTINUED TAXIING. I WAS GOING THROUGH AN EXPLANATION OF THE TKOF THAT MY INSTRUCTOR HAD GIVEN ME. WHEN I HAD FINISHED, WE WERE JUST PULLING INTO A HOLD SHORT POS. WE THEN SWITCHED TO TWR FREQ. I THEN HEARD THE CTLR SAY WHAT I PERCEIVED AS OUR ACFT NUMBER AND THE CLRNC 'CLRED FOR TKOF, RWY 19L, FLY RWY HDG, I'LL CALL YOUR R TURN.' I THEN REPEATED BACK OUR CALL SIGN AND 'CLRED FOR TKOF, ON THE L' AS WE ROLLED ONTO THE RWY AND ADDED PWR. WHEN WE WERE APPROX 500 FT AGL ON THE UPWIND, WE WERE ADVISED BY TWR THAT SHE DIDN'T RELEASE US FOR TKOF. SHE THEN INSTRUCTED US TO CONTACT RADAR ADVISORIES, WHICH WE DID. THE FLT CONTINUED UNEVENTFUL TILL TERMINATION. IN RETROSPECT, I THINK THE PROB COULD POSSIBLY HAVE BEEN AVOIDED BY TUNING IN TWR SOONER, OR BY NOT BEING HANDED OFF PREMATURELY. SECONDLY, I SHOULD HAVE INSISTED ON AN ANSWER TO MY QUERY 'CLRED FOR TKOF ON THE L.' IT IS UNCLR WHY THE CTLR USED OUR CALL SIGN ON CALL UP, WHICH I BELIEVE SHE DID. ATTN TO DETAIL AND MORE CARE IN ASCERTAINING CLRNCS COULD HAVE HELPED AS WELL.

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.