Narrative:

Communications with ground control were excellent. After repeating my IFR clearance (I routinely file IFR), upon receiving permission to taxi to intersection 'M,' I cautioned the ground controller to keep an eye on us, inasmuch as we were first time strangers. I believe I saw a small aircraft precede me to intersection 'M,' which helped give me a subconscious impression that the airliner located at the extreme end of runway 35R was parked, which to my mind explained to me why I was given an intersection position for takeoff, which I did not request. After runup, I advised the tower controller that I was ready for takeoff. She told me to hold short. My aircraft had not moved since I parked for the runup. I continued to hold until I heard an instruction???? 'Cleared for takeoff without a delay.' I actually did not hear the call sign clearly, however, it is not usual in my experience to hear a controller tell an airliner to takeoff without delay, so I assumed the directive was for me. I replied, 'X is rolling,' which I always say at this time. There was no reply from that communication. I immediately rolled into position over the short distance and promptly took off. I was about 400 ft airborne when the lady controller advised me that the instruction was for another aircraft -- the airliner. I of course was mortified and surprised, yet immediately apologized, explaining that I thought the instruction was for me, and voiced my serious concern. The cabin loudspeaker is on the ceiling positioned slightly in favor of the copilot seat where my sister was sitting. She also did not hear any communications other than those described above. As to how incidents such as this might be minimized, I believe all of us who participate in the communications talk entirely too fast. Many use unwarranted abbreviations and provide cryptic messages which can be unfamiliar, especially to transient pilots. Accents in various parts of the country are also a factor. The system encourages rapid staccato speech, particularly at congested times and in congested area. A message delivered rapidly may have to be repeated several times to achieve comprehension, hence, speaking slowly, deliberately and distinctly would actually save time and ensure comprehension.

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Original NASA ASRS Text

Title: TKOF WITHOUT CLRNC. MISUNDERSTOOD COM.

Narrative: COMS WITH GND CTL WERE EXCELLENT. AFTER REPEATING MY IFR CLRNC (I ROUTINELY FILE IFR), UPON RECEIVING PERMISSION TO TAXI TO INTXN 'M,' I CAUTIONED THE GND CTLR TO KEEP AN EYE ON US, INASMUCH AS WE WERE FIRST TIME STRANGERS. I BELIEVE I SAW A SMALL ACFT PRECEDE ME TO INTXN 'M,' WHICH HELPED GIVE ME A SUBCONSCIOUS IMPRESSION THAT THE AIRLINER LOCATED AT THE EXTREME END OF RWY 35R WAS PARKED, WHICH TO MY MIND EXPLAINED TO ME WHY I WAS GIVEN AN INTXN POS FOR TKOF, WHICH I DID NOT REQUEST. AFTER RUNUP, I ADVISED THE TWR CTLR THAT I WAS READY FOR TKOF. SHE TOLD ME TO HOLD SHORT. MY ACFT HAD NOT MOVED SINCE I PARKED FOR THE RUNUP. I CONTINUED TO HOLD UNTIL I HEARD AN INSTRUCTION???? 'CLRED FOR TKOF WITHOUT A DELAY.' I ACTUALLY DID NOT HEAR THE CALL SIGN CLRLY, HOWEVER, IT IS NOT USUAL IN MY EXPERIENCE TO HEAR A CTLR TELL AN AIRLINER TO TKOF WITHOUT DELAY, SO I ASSUMED THE DIRECTIVE WAS FOR ME. I REPLIED, 'X IS ROLLING,' WHICH I ALWAYS SAY AT THIS TIME. THERE WAS NO REPLY FROM THAT COM. I IMMEDIATELY ROLLED INTO POS OVER THE SHORT DISTANCE AND PROMPTLY TOOK OFF. I WAS ABOUT 400 FT AIRBORNE WHEN THE LADY CTLR ADVISED ME THAT THE INSTRUCTION WAS FOR ANOTHER ACFT -- THE AIRLINER. I OF COURSE WAS MORTIFIED AND SURPRISED, YET IMMEDIATELY APOLOGIZED, EXPLAINING THAT I THOUGHT THE INSTRUCTION WAS FOR ME, AND VOICED MY SERIOUS CONCERN. THE CABIN LOUDSPEAKER IS ON THE CEILING POSITIONED SLIGHTLY IN FAVOR OF THE COPLT SEAT WHERE MY SISTER WAS SITTING. SHE ALSO DID NOT HEAR ANY COMS OTHER THAN THOSE DESCRIBED ABOVE. AS TO HOW INCIDENTS SUCH AS THIS MIGHT BE MINIMIZED, I BELIEVE ALL OF US WHO PARTICIPATE IN THE COMS TALK ENTIRELY TOO FAST. MANY USE UNWARRANTED ABBREVIATIONS AND PROVIDE CRYPTIC MESSAGES WHICH CAN BE UNFAMILIAR, ESPECIALLY TO TRANSIENT PLTS. ACCENTS IN VARIOUS PARTS OF THE COUNTRY ARE ALSO A FACTOR. THE SYS ENCOURAGES RAPID STACCATO SPEECH, PARTICULARLY AT CONGESTED TIMES AND IN CONGESTED AREA. A MESSAGE DELIVERED RAPIDLY MAY HAVE TO BE REPEATED SEVERAL TIMES TO ACHIEVE COMPREHENSION, HENCE, SPEAKING SLOWLY, DELIBERATELY AND DISTINCTLY WOULD ACTUALLY SAVE TIME AND ENSURE COMPREHENSION.

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.