LOW TIME PVT C172 PLT CROSSES THE EXTENDED HOLD SHORT LINE FOR RWY 27 AFTER RUN-UP AND PRIOR TO CALLING TWR FOR TKOF CLRNC AT IPT; PA.

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ON JUN/MON/04; MY ACFT WAS PARKED ON THE APRON NEAR THE FIRE DEPT AT THE WILLIAMSPORT ARPT (IPT); PA. AT APPROX XA15 I CONTACTED GND CTL AND REQUESTED CLRNC FOR A VFR DEP TO THE W. I WAS INSTRUCTED TO TAXI TO RWY 27. SINCE THIS WAS MY FIRST VISIT TO THIS ARPT; AND SINCE I HAD ARRIVED ON RWY 30; I ADVISED GND CTL THAT THIS WAS MY FIRST VISIT TO THIS ARPT AND REQUESTED PROGRESSIVE TAXI INSTRUCTIONS. I WAS ADVISED TO TURN L ONTO TXWY A AND TAXI TO THE HOLD SHORT LINE FOR RWY 27B AT THE END OF TXWY A. I PROCEEDED TO TAXI ON TXWY A EXPECTING TO ENCOUNTER THE HOLD SHORT LINE AT THE END OF THIS LONG TXWY. HOWEVER; I ENCOUNTERED THE HOLD SHORT LINE SOONER THAN EXPECTED. I STOPPED AT THE HOLD SHORT LINE AND PERFORMED MY PRE TKOF CHKLIST AT THIS LOCATION. ONCE MY PREFLT CHKLIST WAS COMPLETE; I SWITCHED TO THE TWR FREQ AND BEGAN TO MOVE DOWN THE TXWY. THIS IS WHERE I MADE MY ERROR -- I MOVED MY ACFT TO TAXI TO THE HOLD SHORT LINE WHEN IN FACT I ALREADY WAS AT THE HOLD SHORT LINE. THEREFORE; I CROSSED THE HOLD SHORT LINE WITHOUT PERMISSION FROM THE CTL TWR. I ALMOST IMMEDIATELY REALIZED MY MISTAKE AND STOPPED MY ACFT ON TXWY A APPROX 50 FT BEYOND THE HOLD SHORT LINE AND STILL WELL SHORT OF THE END OF RWY 27. I THEN CONTACTED THE TWR AND ADVISED THEM THAT I WAS READY TO TAKE OFF ON RWY 27. THE TWR INQUIRED WHO HAD GIVEN ME PERMISSION TO CROSS THE HOLD SHORT LINE AND I CONFESSED THAT NOBODY HAD GIVEN ME PERMISSION TO DO SO. I ALSO APOLOGIZED TO THE CTLR FOR MY ERROR. HE THEN GAVE ME PERMISSION TO TAKE OFF ON RWY 27; AT WHICH TIME I AGAIN MOVED MY ACFT FORWARD ON TXWY A TO RWY 27. MY ERROR WAS ENTIRELY MY FAULT. I BELIEVE IT WAS CAUSED BY 1) MY NOT BEING FAMILIAR WITH THE ARPT; 2) MY ENCOUNTERING THE HOLD SHORT LINE SOONER THAN EXPECTED; 3) NOT ENCOUNTERING A 'RUN-UP AREA' PRIOR TO ENCOUNTERING THE HOLD SHORT LINE; AND 4) MY MOVING MY ACFT AT THE END OF MY PREFLT RUN-UP AS I TYPICALLY DO AT MY HOME ARPT. THIS INCIDENT HAS BEEN A TREMENDOUS LEARNING EXPERIENCE FOR ME SINCE I KNOW MY ACTION COULD HAVE IMPACTED FLT SAFETY. I WILL NEVER AGAIN APCH A HOLD SHORT LINE WITHOUT REMEMBERING THE LESSON I LEARNED FROM MY ACTIONS THIS DAY.