Narrative:

Parked on the ramp in front of FBO, I called the tower (PDT) that I was ready to taxi for departure to the west. The tower replied that I should taxi to runway 29. I passed turnoff taxiway east to runway 29 which at that point would have reduced the runway length by about 1/4. (Density altitude was 2700 ft.) the tower asked if I needed the entire runway and I replied affirmative. The tower also indicated that I might like to do my run-up at this point, which I did. After completion of the run-up and being at this airport for the first time, I requested assistance to the beginning of this particular runway. The tower indicated that the runway was in front of my nose and that I should turn right. Upon arriving at this point, I noted the runway 29 numbers and turned right and back taxied for a short distance to get into position for departure. I felt that, after all the assistance given, I was ready to depart, and did so (in the flight guide it stated that 'tower cannot see intersection runway 29 and terminal ramp), even though I do not recall getting back any message, such as 'taxi into position and hold.' after reaching pattern altitude the tower informed me that I had left without proper clearance and that I was to maintain heading since there was traffic to my left approaching runway 7. I indicated that I had traffic in sight and was then given permission to alter my course at my discretion after traffic had passed. Even though I assumed that my original intent was well known regarding departure, plus having been assisted by the tower to the point of departure in a new and unfamiliar airport, nevertheless it still remains the obligation and duty of the PIC to act and move only when instructed by the tower to do so. Clearly spoken and understood communications are vital at all times.

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Original NASA ASRS Text

Title: C182 PLT TOOK OFF WITHOUT CLRNC DUE TO MISUNDERSTANDING IN USING PROGRESSIVE TAXI INSTRUCTIONS.

Narrative: PARKED ON THE RAMP IN FRONT OF FBO, I CALLED THE TWR (PDT) THAT I WAS READY TO TAXI FOR DEP TO THE W. THE TWR REPLIED THAT I SHOULD TAXI TO RWY 29. I PASSED TURNOFF TXWY E TO RWY 29 WHICH AT THAT POINT WOULD HAVE REDUCED THE RWY LENGTH BY ABOUT 1/4. (DENSITY ALT WAS 2700 FT.) THE TWR ASKED IF I NEEDED THE ENTIRE RWY AND I REPLIED AFFIRMATIVE. THE TWR ALSO INDICATED THAT I MIGHT LIKE TO DO MY RUN-UP AT THIS POINT, WHICH I DID. AFTER COMPLETION OF THE RUN-UP AND BEING AT THIS ARPT FOR THE FIRST TIME, I REQUESTED ASSISTANCE TO THE BEGINNING OF THIS PARTICULAR RWY. THE TWR INDICATED THAT THE RWY WAS IN FRONT OF MY NOSE AND THAT I SHOULD TURN R. UPON ARRIVING AT THIS POINT, I NOTED THE RWY 29 NUMBERS AND TURNED R AND BACK TAXIED FOR A SHORT DISTANCE TO GET INTO POS FOR DEP. I FELT THAT, AFTER ALL THE ASSISTANCE GIVEN, I WAS READY TO DEPART, AND DID SO (IN THE FLT GUIDE IT STATED THAT 'TWR CANNOT SEE INTXN RWY 29 AND TERMINAL RAMP), EVEN THOUGH I DO NOT RECALL GETTING BACK ANY MESSAGE, SUCH AS 'TAXI INTO POS AND HOLD.' AFTER REACHING PATTERN ALT THE TWR INFORMED ME THAT I HAD LEFT WITHOUT PROPER CLRNC AND THAT I WAS TO MAINTAIN HDG SINCE THERE WAS TFC TO MY L APCHING RWY 7. I INDICATED THAT I HAD TFC IN SIGHT AND WAS THEN GIVEN PERMISSION TO ALTER MY COURSE AT MY DISCRETION AFTER TFC HAD PASSED. EVEN THOUGH I ASSUMED THAT MY ORIGINAL INTENT WAS WELL KNOWN REGARDING DEP, PLUS HAVING BEEN ASSISTED BY THE TWR TO THE POINT OF DEP IN A NEW AND UNFAMILIAR ARPT, NEVERTHELESS IT STILL REMAINS THE OBLIGATION AND DUTY OF THE PIC TO ACT AND MOVE ONLY WHEN INSTRUCTED BY THE TWR TO DO SO. CLRLY SPOKEN AND UNDERSTOOD COMS ARE VITAL AT ALL TIMES.

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.