Narrative:

I was 'holding short' runway 8R awaiting takeoff clearance. Tower controller (120.90) came on and said, taxi into position and hold. I read 'back position and hold runway 8R.' on the way to the runway, tower controller said, amend instructions, fly runway heading maintain 4000 ft cleared for takeoff. I read back the instructions and proceeded with the takeoff. On climb out, tower controller said there had been a pilot deviation and he gave me the phone number to call when I landed. I phoned phoenix tower and I discussed the situation. He indicated to me that I was not cleared for takeoff and that the readback of my clearance was 'stepped on' by another aircraft. Said that the FSDO would investigate the incident and that I would be contacted at a later date. I would never blatantly disregard an far and takeoff without a takeoff clearance.

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Original NASA ASRS Text

Title: A METRO III FREIGHTER CREW APPARENTLY TOOK OFF FROM PHX WITHOUT AUTH AND THE LCL FSDO IS INVESTIGATING. THE RPTR SAID THAT HE RECEIVED TKOF CLRNC ALONG WITH A CLBOUT HEADING.

Narrative: I WAS 'HOLDING SHORT' RWY 8R AWAITING TKOF CLRNC. TWR CTLR (120.90) CAME ON AND SAID, TAXI INTO POS AND HOLD. I READ 'BACK POS AND HOLD RWY 8R.' ON THE WAY TO THE RWY, TWR CTLR SAID, AMEND INSTRUCTIONS, FLY RWY HEADING MAINTAIN 4000 FT CLRED FOR TKOF. I READ BACK THE INSTRUCTIONS AND PROCEEDED WITH THE TKOF. ON CLBOUT, TWR CTLR SAID THERE HAD BEEN A PLTDEV AND HE GAVE ME THE PHONE NUMBER TO CALL WHEN I LANDED. I PHONED PHOENIX TWR AND I DISCUSSED THE SIT. HE INDICATED TO ME THAT I WAS NOT CLRED FOR TKOF AND THAT THE READBACK OF MY CLRNC WAS 'STEPPED ON' BY ANOTHER ACFT. SAID THAT THE FSDO WOULD INVESTIGATE THE INCIDENT AND THAT I WOULD BE CONTACTED AT A LATER DATE. I WOULD NEVER BLATANTLY DISREGARD AN FAR AND TKOF WITHOUT A TKOF CLRNC.

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.