Single pilot thinking he had takeoff clearance, was told otherwise by tower.

Attributes
ACN	493064
Time
Date	200011
Day	Sat
Local Time Of Day	0601 To 1200
Place
State Reference	AZ
Altitude	agl bound upper : 400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	climbout : takeoff ground : holding ground : takeoff roll
Route In Use	approach : visual
Flight Plan	VFR
Aircraft 2
Controlling Facilities	tower : gyr.tower
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	ground : taxi landing : roll
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 25 flight time total : 200 flight time type : 200
ASRS Report	493064
Person 2
Function	flight crew : single pilot
Qualification	pilot : student
Events
Anomaly	ground encounters other non adherence : published procedure non adherence : clearance non adherence : far other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance none taken : anomaly accepted none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew other other
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

After receiving instructions to take position and hold, the tower was having a lengthy conversation with the aircraft that had just landed ahead of me and was taxiing to main terminal, I assumed I was cleared for takeoff when the tower started to say 'aircraft X', but then resumed the conversation with the taxiing aircraft. The taxiing aircraft had turned off the approximately 8000 ft runway. While the tower was focused on the heated discussion with the taxiing aircraft, he again said 'aircraft X cleared for takeoff.' a few seconds later the tower came back and asked 'aircraft X, how did you get airborne?' I replied that I thought I had been cleared for takeoff. Tower then instructed me to do a full stop landing, lock down the aircraft and call the tower, to which I complied. I feel this incident occurred because the tower was having a lengthy conversation with the taxiing aircraft rather than turning him over to ground control, causing confusion on my part.

Original NASA ASRS Text

Title: SINGLE PLT THINKING HE HAD TKOF CLRNC, WAS TOLD OTHERWISE BY TWR.

Narrative: AFTER RECEIVING INSTRUCTIONS TO TAKE POS AND HOLD, THE TWR WAS HAVING A LENGTHY CONVERSATION WITH THE ACFT THAT HAD JUST LANDED AHEAD OF ME AND WAS TAXIING TO MAIN TERMINAL, I ASSUMED I WAS CLRED FOR TKOF WHEN THE TWR STARTED TO SAY 'ACFT X', BUT THEN RESUMED THE CONVERSATION WITH THE TAXIING ACFT. THE TAXIING ACFT HAD TURNED OFF THE APPROX 8000 FT RWY. WHILE THE TWR WAS FOCUSED ON THE HEATED DISCUSSION WITH THE TAXIING ACFT, HE AGAIN SAID 'ACFT X CLRED FOR TKOF.' A FEW SECONDS LATER THE TWR CAME BACK AND ASKED 'ACFT X, HOW DID YOU GET AIRBORNE?' I REPLIED THAT I THOUGHT I HAD BEEN CLRED FOR TKOF. TWR THEN INSTRUCTED ME TO DO A FULL STOP LNDG, LOCK DOWN THE ACFT AND CALL THE TWR, TO WHICH I COMPLIED. I FEEL THIS INCIDENT OCCURRED BECAUSE THE TWR WAS HAVING A LENGTHY CONVERSATION WITH THE TAXIING ACFT RATHER THAN TURNING HIM OVER TO GND CTL, CAUSING CONFUSION ON MY PART.

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.