Narrative:

Parked at ramp at extreme southeast corner of la crosse municipal airport. Contacted ground control and cleared to taxi and hold short of runway 3-36. Complied. Called tower and received clearance for takeoff with left turn out. Crossed runway 'hold clear' lines, lined up, called 'rolling', added power and proceeded to takeoff. At approximately 400 ft AGL tower advised 'hold present altitude and heading.' I acknowledged. Tower then asked if I knew that I had departed on taxiway and if I heard the takeoff clearance cancellation. I answered 'no' to both questions. On hearing these xmissions, an small aircraft which had departed moments prior, advised tower that the runway/taxiway markings were very 'ambiguous.' the referenced 'hold short' markings are short of the taxiway that parallels runway 3/21. This contributed to my error. I noticed nothing dangerous as I had a clear field of view and was airborne in about 400 ft on a long and wide taxiway. This was, however, a serious error on my part. Callback conversation with reporter revealed the following information. Reporter states he was unable to get airport diagram from FBO. These are usually available in the pilots briefing rooms. Feels if he had one he would not have made the mistake. He was cleared for takeoff from the runup area. Would have had to cross runway 36 to get to runway 3. When he saw the taxiway that parallels 3 he turned and took off. Feels a sign to indicate area is a taxiway would help avoid confusion.

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Original NASA ASRS Text

Title: PLT CONFUSED AT RWY INTXN TAKES OFF ON TAXIWAY.

Narrative: PARKED AT RAMP AT EXTREME SE CORNER OF LA CROSSE MUNI ARPT. CONTACTED GND CTL AND CLRED TO TAXI AND HOLD SHORT OF RWY 3-36. COMPLIED. CALLED TWR AND RECEIVED CLRNC FOR TKOF WITH L TURN OUT. CROSSED RWY 'HOLD CLR' LINES, LINED UP, CALLED 'ROLLING', ADDED PWR AND PROCEEDED TO TKOF. AT APPROX 400 FT AGL TWR ADVISED 'HOLD PRESENT ALT AND HDG.' I ACKNOWLEDGED. TWR THEN ASKED IF I KNEW THAT I HAD DEPARTED ON TAXIWAY AND IF I HEARD THE TKOF CLRNC CANCELLATION. I ANSWERED 'NO' TO BOTH QUESTIONS. ON HEARING THESE XMISSIONS, AN SMA WHICH HAD DEPARTED MOMENTS PRIOR, ADVISED TWR THAT THE RWY/TAXIWAY MARKINGS WERE VERY 'AMBIGUOUS.' THE REFERENCED 'HOLD SHORT' MARKINGS ARE SHORT OF THE TAXIWAY THAT PARALLELS RWY 3/21. THIS CONTRIBUTED TO MY ERROR. I NOTICED NOTHING DANGEROUS AS I HAD A CLR FIELD OF VIEW AND WAS AIRBORNE IN ABOUT 400 FT ON A LONG AND WIDE TAXIWAY. THIS WAS, HOWEVER, A SERIOUS ERROR ON MY PART. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR STATES HE WAS UNABLE TO GET ARPT DIAGRAM FROM FBO. THESE ARE USUALLY AVAILABLE IN THE PLTS BRIEFING ROOMS. FEELS IF HE HAD ONE HE WOULD NOT HAVE MADE THE MISTAKE. HE WAS CLRED FOR TKOF FROM THE RUNUP AREA. WOULD HAVE HAD TO CROSS RWY 36 TO GET TO RWY 3. WHEN HE SAW THE TAXIWAY THAT PARALLELS 3 HE TURNED AND TOOK OFF. FEELS A SIGN TO INDICATE AREA IS A TAXIWAY WOULD HELP AVOID CONFUSION.

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.