Narrative:

I was departing for an IFR flight back to home base. After the usual preflight, warm up and clearance delivery I was instructed to runway 31 for departure. Runway 31 is right next to runway 30R and next to FBO, so it sits between them. Coming out of FBO is a short intersection to runway 31 which I exited on. There is no taxiway to the departure end of runway 31 so it is necessary to back-taxi the runway. While taxiing, the ground controller inquired if I would be ready at the end. I responded, 'no, I'll need a couple of mins for runup.' it was around this time that my mind became committed to 'force of habit' mode, which resulted in a major mistake. I am normally used to using a regular taxiway to get to a departure end since those are most common where I usually fly. I rarely have to back- taxi. Through 'force of habit,' not enough attention paid, and a little unfamiliarity with the field, I forgot that I was taxiing on a runway and believed I was in fact on a taxiway. At the end of runway 31 is an intersection to runway 30R. Runway 30R almost parallels runway 31, of course, and not paying attention, I proceeded into a runup position for runway 30R thinking it was the runway 31 I had just taxied on. When finished, I called tower for departure and was 'cleared for departure on runway 31.' so out I went onto runway 30R with my head still complacent with the situation. Making the 90 degree turn I looked over my shoulder to see a commercial jetliner on a 3/4 - 1 mi final for runway 30R. I remember thinking it was odd they let me go with that out there. I expedited takeoff run. There was no time for an evasive turn to correct my error, and really nowhere to turn for that matter. I kept going to try and get airborne and out of the way. The tower realized what I was doing while on the roll and scrambled to give directives which finalized in 'cleared for takeoff on runway 30R.' although st louis tower did not notice my mistake until too late, I obviously made it nonetheless. In my 670+ hours of flying, I've experienced the largest, most congested fields this country has to offer in fixed wings ranging from cessna 150's to the conquest ii. I regularly copilot the conquest and get plenty of left seat time. My pilot license is a multi engine/instrument/commercial. The only reasons for this incident are lack of attention, force of habit, and a little unfamiliarity. Each by themselves can be and are dangerous enough. I hope this does not affect my future too harshly.

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Original NASA ASRS Text

Title: SMA PLT DEPARTS ON WRONG RWY, RWY 30R INSTEAD OF RWY 31.

Narrative: I WAS DEPARTING FOR AN IFR FLT BACK TO HOME BASE. AFTER THE USUAL PREFLT, WARM UP AND CLRNC DELIVERY I WAS INSTRUCTED TO RWY 31 FOR DEP. RWY 31 IS RIGHT NEXT TO RWY 30R AND NEXT TO FBO, SO IT SITS BTWN THEM. COMING OUT OF FBO IS A SHORT INTXN TO RWY 31 WHICH I EXITED ON. THERE IS NO TXWY TO THE DEP END OF RWY 31 SO IT IS NECESSARY TO BACK-TAXI THE RWY. WHILE TAXIING, THE GND CTLR INQUIRED IF I WOULD BE READY AT THE END. I RESPONDED, 'NO, I'LL NEED A COUPLE OF MINS FOR RUNUP.' IT WAS AROUND THIS TIME THAT MY MIND BECAME COMMITTED TO 'FORCE OF HABIT' MODE, WHICH RESULTED IN A MAJOR MISTAKE. I AM NORMALLY USED TO USING A REGULAR TXWY TO GET TO A DEP END SINCE THOSE ARE MOST COMMON WHERE I USUALLY FLY. I RARELY HAVE TO BACK- TAXI. THROUGH 'FORCE OF HABIT,' NOT ENOUGH ATTN PAID, AND A LITTLE UNFAMILIARITY WITH THE FIELD, I FORGOT THAT I WAS TAXIING ON A RWY AND BELIEVED I WAS IN FACT ON A TXWY. AT THE END OF RWY 31 IS AN INTXN TO RWY 30R. RWY 30R ALMOST PARALLELS RWY 31, OF COURSE, AND NOT PAYING ATTN, I PROCEEDED INTO A RUNUP POS FOR RWY 30R THINKING IT WAS THE RWY 31 I HAD JUST TAXIED ON. WHEN FINISHED, I CALLED TWR FOR DEP AND WAS 'CLRED FOR DEP ON RWY 31.' SO OUT I WENT ONTO RWY 30R WITH MY HEAD STILL COMPLACENT WITH THE SIT. MAKING THE 90 DEG TURN I LOOKED OVER MY SHOULDER TO SEE A COMMERCIAL JETLINER ON A 3/4 - 1 MI FINAL FOR RWY 30R. I REMEMBER THINKING IT WAS ODD THEY LET ME GO WITH THAT OUT THERE. I EXPEDITED TKOF RUN. THERE WAS NO TIME FOR AN EVASIVE TURN TO CORRECT MY ERROR, AND REALLY NOWHERE TO TURN FOR THAT MATTER. I KEPT GOING TO TRY AND GET AIRBORNE AND OUT OF THE WAY. THE TWR REALIZED WHAT I WAS DOING WHILE ON THE ROLL AND SCRAMBLED TO GIVE DIRECTIVES WHICH FINALIZED IN 'CLRED FOR TKOF ON RWY 30R.' ALTHOUGH ST LOUIS TWR DID NOT NOTICE MY MISTAKE UNTIL TOO LATE, I OBVIOUSLY MADE IT NONETHELESS. IN MY 670+ HRS OF FLYING, I'VE EXPERIENCED THE LARGEST, MOST CONGESTED FIELDS THIS COUNTRY HAS TO OFFER IN FIXED WINGS RANGING FROM CESSNA 150'S TO THE CONQUEST II. I REGULARLY COPLT THE CONQUEST AND GET PLENTY OF L SEAT TIME. MY PLT LICENSE IS A MULTI ENG/INST/COMMERCIAL. THE ONLY REASONS FOR THIS INCIDENT ARE LACK OF ATTN, FORCE OF HABIT, AND A LITTLE UNFAMILIARITY. EACH BY THEMSELVES CAN BE AND ARE DANGEROUS ENOUGH. I HOPE THIS DOES NOT AFFECT MY FUTURE TOO HARSHLY.

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.