Narrative:

I allowed circumstances to override my rule of 'think before you speak.' we were at the threshold end of a very long runway of more than 12000 ft at a major airport in a little 4 place cessna where at XA00 the traffic was almost nil. After a long wait between 'taxi into position' and 'takeoff' instructions I found myself saying I was starting a takeoff roll, when my rule of 'think before you speak' would have dictated to confirm first and say 'in position and holding' for a second time or 'confirm, cleared for takeoff.' from our original position well back of the hold line, when we were ready we had watched a medium sized business aircraft land. The wind was 3 KTS or less and there had been no traffic for the previous 10 mins when tower cleared us 'into position and hold.' I repeated that clearance and said we would move out slowly in the 4 place cessna to let any wake turbulence from the landing aircraft dissipate. I taxied very slowly out to runway center just in front of the threshold lights. By then, probably nearly 2 mins had passed since the original clearance had been issued into position. As we sat looking down the runway it appeared that the arriving aircraft had gone to the very far end of this 12190 ft runway before turning left toward the GA parking area because of construction on the left runway. Clearly that airplane was slowly turning off about 2 mi down there. For some reason, a quiet night, and perhaps some distraction loading the 2 passenger, I found myself saying 'rolling for takeoff.' almost at the same instant my copilot pointed out that we had not yet been cleared for takeoff. We had rolled a few ft but I promptly applied brakes, stopped and told the tower we were holding in position on runway 26R. The poised and very capable tower operator's words met mine at the same moment saying 'you were not cleared for takeoff.' I repeated back a second time, 'holding in position.' a very few seconds later, the tower cleared us for takeoff, which I repeated back and the rest of the flight went along uneventfully. Our plane had moved only a few ft. There was no safety hazard. The arriving aircraft was off the runway and far away. But, I had momentarily allowed other things to subordinate my consciousness of the communications and skip my rule of 'think before you speak.' night/early morning conditions of possible fog or lowering overcast, and the recent attention to a passenger need, while the airport was unusually quiet with minimal traffic and the long time lapse between communications, I let my subconscious get into my conscious operations and I momentarily skipped my rules about think first, and if in doubt, reconfirm before transmitting. This experience will certainly enhance my guard against letting unexpected sits and long quiet times or night conditions lower the focus on conscious procedures.

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Original NASA ASRS Text

Title: A VERY SHORT TKOF ROLL DURING A NIGHT OP WAS ABORTED WHEN THE PLT OF A C172 REALIZED THAT THE CLRNC FOR TKOF HAD NOT BEEN ISSUED BY THE TWR AT ONT, CA.

Narrative: I ALLOWED CIRCUMSTANCES TO OVERRIDE MY RULE OF 'THINK BEFORE YOU SPEAK.' WE WERE AT THE THRESHOLD END OF A VERY LONG RWY OF MORE THAN 12000 FT AT A MAJOR ARPT IN A LITTLE 4 PLACE CESSNA WHERE AT XA00 THE TFC WAS ALMOST NIL. AFTER A LONG WAIT BTWN 'TAXI INTO POS' AND 'TKOF' INSTRUCTIONS I FOUND MYSELF SAYING I WAS STARTING A TKOF ROLL, WHEN MY RULE OF 'THINK BEFORE YOU SPEAK' WOULD HAVE DICTATED TO CONFIRM FIRST AND SAY 'IN POS AND HOLDING' FOR A SECOND TIME OR 'CONFIRM, CLRED FOR TKOF.' FROM OUR ORIGINAL POS WELL BACK OF THE HOLD LINE, WHEN WE WERE READY WE HAD WATCHED A MEDIUM SIZED BUSINESS ACFT LAND. THE WIND WAS 3 KTS OR LESS AND THERE HAD BEEN NO TFC FOR THE PREVIOUS 10 MINS WHEN TWR CLRED US 'INTO POS AND HOLD.' I REPEATED THAT CLRNC AND SAID WE WOULD MOVE OUT SLOWLY IN THE 4 PLACE CESSNA TO LET ANY WAKE TURB FROM THE LNDG ACFT DISSIPATE. I TAXIED VERY SLOWLY OUT TO RWY CTR JUST IN FRONT OF THE THRESHOLD LIGHTS. BY THEN, PROBABLY NEARLY 2 MINS HAD PASSED SINCE THE ORIGINAL CLRNC HAD BEEN ISSUED INTO POS. AS WE SAT LOOKING DOWN THE RWY IT APPEARED THAT THE ARRIVING ACFT HAD GONE TO THE VERY FAR END OF THIS 12190 FT RWY BEFORE TURNING L TOWARD THE GA PARKING AREA BECAUSE OF CONSTRUCTION ON THE L RWY. CLRLY THAT AIRPLANE WAS SLOWLY TURNING OFF ABOUT 2 MI DOWN THERE. FOR SOME REASON, A QUIET NIGHT, AND PERHAPS SOME DISTR LOADING THE 2 PAX, I FOUND MYSELF SAYING 'ROLLING FOR TKOF.' ALMOST AT THE SAME INSTANT MY COPLT POINTED OUT THAT WE HAD NOT YET BEEN CLRED FOR TKOF. WE HAD ROLLED A FEW FT BUT I PROMPTLY APPLIED BRAKES, STOPPED AND TOLD THE TWR WE WERE HOLDING IN POS ON RWY 26R. THE POISED AND VERY CAPABLE TWR OPERATOR'S WORDS MET MINE AT THE SAME MOMENT SAYING 'YOU WERE NOT CLRED FOR TKOF.' I REPEATED BACK A SECOND TIME, 'HOLDING IN POS.' A VERY FEW SECONDS LATER, THE TWR CLRED US FOR TKOF, WHICH I REPEATED BACK AND THE REST OF THE FLT WENT ALONG UNEVENTFULLY. OUR PLANE HAD MOVED ONLY A FEW FT. THERE WAS NO SAFETY HAZARD. THE ARRIVING ACFT WAS OFF THE RWY AND FAR AWAY. BUT, I HAD MOMENTARILY ALLOWED OTHER THINGS TO SUBORDINATE MY CONSCIOUSNESS OF THE COMS AND SKIP MY RULE OF 'THINK BEFORE YOU SPEAK.' NIGHT/EARLY MORNING CONDITIONS OF POSSIBLE FOG OR LOWERING OVCST, AND THE RECENT ATTN TO A PAX NEED, WHILE THE ARPT WAS UNUSUALLY QUIET WITH MINIMAL TFC AND THE LONG TIME LAPSE BTWN COMS, I LET MY SUBCONSCIOUS GET INTO MY CONSCIOUS OPS AND I MOMENTARILY SKIPPED MY RULES ABOUT THINK FIRST, AND IF IN DOUBT, RECONFIRM BEFORE XMITTING. THIS EXPERIENCE WILL CERTAINLY ENHANCE MY GUARD AGAINST LETTING UNEXPECTED SITS AND LONG QUIET TIMES OR NIGHT CONDITIONS LOWER THE FOCUS ON CONSCIOUS PROCS.

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.