Narrative:

I departed san patricio county airport (T69), sinton, tx, in a cessna 150 on the 1ST leg of a solo cross country bound for mcallen miller international (mfe), mcallen tx. The en route flight from sinton to mcallen was routine and without incident. The WX was generally good VFR but became a little hazier as I approached mcallen. I was given radar vector assistance and located the airport about 4 mi away at my 11 O'clock position. I was instructed to contact the tower and I did. I was cleared to land on runway 13 and I complied. Following the landing, I was instructed to depart the runway on taxiway bravo. I requested that ground control provide me with progressive taxi instructions to FBO. I taxied to FBO and refueled. At the time of my departure the tower had changed the runway from runway 13 to runway 31. I once again asked for progressive taxi instructions from mcallen ground control. As I was taxiing out on taxiway charlie the voice of ground controller was that of a woman. I taxied out to the intersection of taxiway charlie and taxiway alpha which runs parallel to the active runway 31. As I was approaching the intersection, the voice on the radio changed from that of a woman to that of a man. In thinking back upon what happened next, I must have mentally made an assumption that I was now talking to the control tower rather than ground control. I cannot recall if I changed frequency on the radio. Having the benefit of subsequently reviewing what happened at mcallen in a telephone conversation with mcallen tower, I now know that I was asked if I wanted to use the entire runway or if I would accept an intersection takeoff. (In which I would have been required to taxi straight ahead across taxiway alpha, then turn right down runway 31 and takeoff.) the mcallen tower told me on the telephone that I didn't reply when I was asked if I wanted an intersection takeoff, and I probably did not since I had never made an intersection takeoff and was confused at this time. What I don't understand is how the tower or ground control could assume I understood what was transmitted if I didn't reply. I was asked if I was ready for takeoff and replied that I was. I was asked this same question a second time and again a third time, and both times I replied in the affirmative. When the tower operator asked me the third time, being confused, I must have assumed this was his way of telling me I was cleared for takeoff. I was really confused and intimidated. When he asked me the third time if I was ready for takeoff, I replied yes and released the brakes, turned to the right to a heading of 310 degrees. Taxiway alpha is a wide and long taxiway and compares to the runway I used for the significant part of my training. As soon as I rotated and was lifting off I realized I had made a mistake and taken off from a taxiway because of the continuous yellow line down the taxiway. There was no traffic on runway 31 or on taxiway alpha in front of me. Because the of fact that I was already airborne, I decided to continue and to line up with runway 31. I looked back behind me and in front and saw no aircraft departing from runway 31. I banked the aircraft left, flew over to runway, and then turned to the right to aline the aircraft with runway 31. I continued to climb straight out on a heading O 310 degrees which is the heading to laredo international airport. As I was climbing out, I was contacted by radio on the same frequency I used prior to takeoff (I now realize it, I still don't know if it was ground control or tower) and notified that I had made an unclred takeoff and that I had taken off from a taxiway (this I already knew). I was given a telephone number and asked to call mcallen tower when I reached my next destination at laredo international. My flight instructor contacted mr. X of the san antonio FSDO and reviewed this matter with him. My flight instructor and I have made plans to fly additional dual at an airport with a control tower and will probably do so within 10 days if the WX allows.

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Original NASA ASRS Text

Title: TXWY UNAUTH TKOF BY STUDENT PLT.

Narrative: I DEPARTED SAN PATRICIO COUNTY ARPT (T69), SINTON, TX, IN A CESSNA 150 ON THE 1ST LEG OF A SOLO XCOUNTRY BOUND FOR MCALLEN MILLER INTL (MFE), MCALLEN TX. THE ENRTE FLT FROM SINTON TO MCALLEN WAS ROUTINE AND WITHOUT INCIDENT. THE WX WAS GENERALLY GOOD VFR BUT BECAME A LITTLE HAZIER AS I APCHED MCALLEN. I WAS GIVEN RADAR VECTOR ASSISTANCE AND LOCATED THE ARPT ABOUT 4 MI AWAY AT MY 11 O'CLOCK POS. I WAS INSTRUCTED TO CONTACT THE TWR AND I DID. I WAS CLRED TO LAND ON RWY 13 AND I COMPLIED. FOLLOWING THE LNDG, I WAS INSTRUCTED TO DEPART THE RWY ON TXWY BRAVO. I REQUESTED THAT GND CTL PROVIDE ME WITH PROGRESSIVE TAXI INSTRUCTIONS TO FBO. I TAXIED TO FBO AND REFUELED. AT THE TIME OF MY DEP THE TWR HAD CHANGED THE RWY FROM RWY 13 TO RWY 31. I ONCE AGAIN ASKED FOR PROGRESSIVE TAXI INSTRUCTIONS FROM MCALLEN GND CTL. AS I WAS TAXIING OUT ON TXWY CHARLIE THE VOICE OF GND CTLR WAS THAT OF A WOMAN. I TAXIED OUT TO THE INTXN OF TXWY CHARLIE AND TXWY ALPHA WHICH RUNS PARALLEL TO THE ACTIVE RWY 31. AS I WAS APCHING THE INTXN, THE VOICE ON THE RADIO CHANGED FROM THAT OF A WOMAN TO THAT OF A MAN. IN THINKING BACK UPON WHAT HAPPENED NEXT, I MUST HAVE MENTALLY MADE AN ASSUMPTION THAT I WAS NOW TALKING TO THE CTL TWR RATHER THAN GND CTL. I CANNOT RECALL IF I CHANGED FREQ ON THE RADIO. HAVING THE BENEFIT OF SUBSEQUENTLY REVIEWING WHAT HAPPENED AT MCALLEN IN A TELEPHONE CONVERSATION WITH MCALLEN TWR, I NOW KNOW THAT I WAS ASKED IF I WANTED TO USE THE ENTIRE RWY OR IF I WOULD ACCEPT AN INTXN TKOF. (IN WHICH I WOULD HAVE BEEN REQUIRED TO TAXI STRAIGHT AHEAD ACROSS TXWY ALPHA, THEN TURN R DOWN RWY 31 AND TKOF.) THE MCALLEN TWR TOLD ME ON THE TELEPHONE THAT I DIDN'T REPLY WHEN I WAS ASKED IF I WANTED AN INTXN TKOF, AND I PROBABLY DID NOT SINCE I HAD NEVER MADE AN INTXN TKOF AND WAS CONFUSED AT THIS TIME. WHAT I DON'T UNDERSTAND IS HOW THE TWR OR GND CTL COULD ASSUME I UNDERSTOOD WHAT WAS XMITTED IF I DIDN'T REPLY. I WAS ASKED IF I WAS READY FOR TKOF AND REPLIED THAT I WAS. I WAS ASKED THIS SAME QUESTION A SECOND TIME AND AGAIN A THIRD TIME, AND BOTH TIMES I REPLIED IN THE AFFIRMATIVE. WHEN THE TWR OPERATOR ASKED ME THE THIRD TIME, BEING CONFUSED, I MUST HAVE ASSUMED THIS WAS HIS WAY OF TELLING ME I WAS CLRED FOR TKOF. I WAS REALLY CONFUSED AND INTIMIDATED. WHEN HE ASKED ME THE THIRD TIME IF I WAS READY FOR TKOF, I REPLIED YES AND RELEASED THE BRAKES, TURNED TO THE R TO A HDG OF 310 DEGS. TXWY ALPHA IS A WIDE AND LONG TXWY AND COMPARES TO THE RWY I USED FOR THE SIGNIFICANT PART OF MY TRAINING. AS SOON AS I ROTATED AND WAS LIFTING OFF I REALIZED I HAD MADE A MISTAKE AND TAKEN OFF FROM A TXWY BECAUSE OF THE CONTINUOUS YELLOW LINE DOWN THE TXWY. THERE WAS NO TFC ON RWY 31 OR ON TXWY ALPHA IN FRONT OF ME. BECAUSE THE OF FACT THAT I WAS ALREADY AIRBORNE, I DECIDED TO CONTINUE AND TO LINE UP WITH RWY 31. I LOOKED BACK BEHIND ME AND IN FRONT AND SAW NO ACFT DEPARTING FROM RWY 31. I BANKED THE ACFT L, FLEW OVER TO RWY, AND THEN TURNED TO THE R TO ALINE THE ACFT WITH RWY 31. I CONTINUED TO CLB STRAIGHT OUT ON A HDG O 310 DEGS WHICH IS THE HDG TO LAREDO INTL ARPT. AS I WAS CLBING OUT, I WAS CONTACTED BY RADIO ON THE SAME FREQ I USED PRIOR TO TKOF (I NOW REALIZE IT, I STILL DON'T KNOW IF IT WAS GND CTL OR TWR) AND NOTIFIED THAT I HAD MADE AN UNCLRED TKOF AND THAT I HAD TAKEN OFF FROM A TXWY (THIS I ALREADY KNEW). I WAS GIVEN A TELEPHONE NUMBER AND ASKED TO CALL MCALLEN TWR WHEN I REACHED MY NEXT DEST AT LAREDO INTL. MY FLT INSTRUCTOR CONTACTED MR. X OF THE SAN ANTONIO FSDO AND REVIEWED THIS MATTER WITH HIM. MY FLT INSTRUCTOR AND I HAVE MADE PLANS TO FLY ADDITIONAL DUAL AT AN ARPT WITH A CTL TWR AND WILL PROBABLY DO SO WITHIN 10 DAYS IF THE WX ALLOWS.

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.