Narrative:

I had a clearance for runway 15L, to hold short on crossing intersecting runway 25, along with altitude information. As I approached the hold short line my clearance was changed to runway 25 with other altitude information. This happened as I was nearing the hold short line. I momentarily took this as an indication to proceed. As I crossed the hold short line, I realized my error and immediately turned the C172 around. As I did this, I was told to turn around, go back to the hold short line and contact tower. On contacting the tower, I was immediately cleared for takeoff. Fortunately, there were no other aircraft landing or taking off.

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Original NASA ASRS Text

Title: A C152 PLT THOUGHT HE WAS CLRED ONTO THE RWY, BUT THEN REALIZED HE WAS NOT AND TURNED THE ACFT AROUND TO EXIT THE RWY.

Narrative: I HAD A CLRNC FOR RWY 15L, TO HOLD SHORT ON XING INTERSECTING RWY 25, ALONG WITH ALT INFO. AS I APCHED THE HOLD SHORT LINE MY CLRNC WAS CHANGED TO RWY 25 WITH OTHER ALT INFO. THIS HAPPENED AS I WAS NEARING THE HOLD SHORT LINE. I MOMENTARILY TOOK THIS AS AN INDICATION TO PROCEED. AS I CROSSED THE HOLD SHORT LINE, I REALIZED MY ERROR AND IMMEDIATELY TURNED THE C172 AROUND. AS I DID THIS, I WAS TOLD TO TURN AROUND, GO BACK TO THE HOLD SHORT LINE AND CONTACT TWR. ON CONTACTING THE TWR, I WAS IMMEDIATELY CLRED FOR TKOF. FORTUNATELY, THERE WERE NO OTHER ACFT LNDG OR TAKING OFF.

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.