C172 pilot has a runway incursion on runway 12R at sat.

Attributes
ACN	698188
Time
Date	200605
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sat.airport
State Reference	TX
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Cessna Single Piston Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	ground : position and hold
Flight Plan	None
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 20 flight time total : 140 flight time type : 120
ASRS Report	698188
Person 2
Function	controller : local
Events
Anomaly	incursion : runway non adherence : clearance non adherence : far
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

The runway incursion happened when I made the mistake of assuming that the word 'roger' was a clearance to take off from runway 12R at sat; tx. I had called the tower twice and informed them that I was ready for takeoff. The response I heard both times was 'roger' with no tail number. I assumed that the tower was in a hurry to get me in the air and out of the way. Luckily; a pilot in a jet behind me informed the tower that 'the cessna was taking the runway.' the tower told me to stop where I was and then asked me if he had given me clearance for takeoff. I responded 'sir; I thought you had.' the tower told me to do a 180 degree turn and wait for further instructions. My inexperience at a busy airport was a contributing factor. I felt like I needed to get out of the way of the jet or jets behind me. I have been taught that 'roger' is not a clearance to do anything.

Original NASA ASRS Text

Title: C172 PLT HAS A RWY INCURSION ON RWY 12R AT SAT.

Narrative: THE RWY INCURSION HAPPENED WHEN I MADE THE MISTAKE OF ASSUMING THAT THE WORD 'ROGER' WAS A CLRNC TO TAKE OFF FROM RWY 12R AT SAT; TX. I HAD CALLED THE TWR TWICE AND INFORMED THEM THAT I WAS READY FOR TKOF. THE RESPONSE I HEARD BOTH TIMES WAS 'ROGER' WITH NO TAIL NUMBER. I ASSUMED THAT THE TWR WAS IN A HURRY TO GET ME IN THE AIR AND OUT OF THE WAY. LUCKILY; A PLT IN A JET BEHIND ME INFORMED THE TWR THAT 'THE CESSNA WAS TAKING THE RWY.' THE TWR TOLD ME TO STOP WHERE I WAS AND THEN ASKED ME IF HE HAD GIVEN ME CLRNC FOR TKOF. I RESPONDED 'SIR; I THOUGHT YOU HAD.' THE TWR TOLD ME TO DO A 180 DEG TURN AND WAIT FOR FURTHER INSTRUCTIONS. MY INEXPERIENCE AT A BUSY ARPT WAS A CONTRIBUTING FACTOR. I FELT LIKE I NEEDED TO GET OUT OF THE WAY OF THE JET OR JETS BEHIND ME. I HAVE BEEN TAUGHT THAT 'ROGER' IS NOT A CLRNC TO DO ANYTHING.

Data retrieved from NASA's ASRS site as of January 2009 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.