Narrative:

I was taxiing toward runway 27L for departure after having departed the gate. We had been told on pushback to expect runway 27R. Upon calling for taxi, we were assigned 27L. The controller initially said to taxi via the inner, then said to go via the outer. Exiting the 'G' concourse area left approximately 100' to be traveled on the outer taxiway if we were to go to it and then it turned right back to the inner. It seemed odd especially with the controller having fumbled with the matter and with the way clear on the inner to the same point en route to 27L. I asked the first officer to ask if we could use the inner taxiway. Before he could, ground told us to follow air carrier B and he (ground) fumbled with whether it was a type a or B (I believe). The first officer acknowledged ground to follow air carrier B and I had to turn onto the outer and continued to follow air carrier B halfway onto the runway 27L displaced threshold, I realized the air carrier B had crossed 27L's displaced threshold and was readying for departure on runway 30. Told him to get a frequency up quick and find out what we were supposed to do. Tower, in a raised voice, told us to verify that we were already on 27L, an active runway. I said that we were, that we had been told to follow air carrier B and asked if he wanted us to follow him to 27L or 30. He said he had wanted us to follow only to 27L. I said it was my mistake and apologized. He cleared us into position and hold. Pertinent is the fact that this was my first trip as captain. My first officer was only about 2 weeks out of training as copilot after at least 6 months sitting at a F/east's panel. Also, our airline just switched operating procedures and checklist style and content. With the confusion of taxiway assignment, change of runways from what we had been told to expect and the use of new flows and checklist procedures, my ability to concentrate on the ground controller's instructions was impaired. The first officer had emphasized that the controller wanted us to follow air carrier B and I expected that he was going to the same runway we were assigned. The displaced threshold of 27L is not real evident as a runway and I had not noticed the hold line that I evidently crossed. I had checked for traffic from my left to rejoin the inner and looked next at the air carrier B and then at my airport diagram (10-9) and realized too late that air carrier B had gone to runway 30 and I was half upon wy 27L's displaced threshold. No known conflict resulted and when I asked the controller if we had a problem, I believe he said 'negative'.

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Original NASA ASRS Text

Title: ACR MLG UNAUTH RWY ENTRY.

Narrative: I WAS TAXIING TOWARD RWY 27L FOR DEP AFTER HAVING DEPARTED THE GATE. WE HAD BEEN TOLD ON PUSHBACK TO EXPECT RWY 27R. UPON CALLING FOR TAXI, WE WERE ASSIGNED 27L. THE CTLR INITIALLY SAID TO TAXI VIA THE INNER, THEN SAID TO GO VIA THE OUTER. EXITING THE 'G' CONCOURSE AREA LEFT APPROX 100' TO BE TRAVELED ON THE OUTER TXWY IF WE WERE TO GO TO IT AND THEN IT TURNED RIGHT BACK TO THE INNER. IT SEEMED ODD ESPECIALLY WITH THE CTLR HAVING FUMBLED WITH THE MATTER AND WITH THE WAY CLEAR ON THE INNER TO THE SAME POINT ENRTE TO 27L. I ASKED THE F/O TO ASK IF WE COULD USE THE INNER TXWY. BEFORE HE COULD, GND TOLD US TO FOLLOW ACR B AND HE (GND) FUMBLED WITH WHETHER IT WAS A TYPE A OR B (I BELIEVE). THE F/O ACKNOWLEDGED GND TO FOLLOW ACR B AND I HAD TO TURN ONTO THE OUTER AND CONTINUED TO FOLLOW ACR B HALFWAY ONTO THE RWY 27L DISPLACED THRESHOLD, I REALIZED THE ACR B HAD CROSSED 27L'S DISPLACED THRESHOLD AND WAS READYING FOR DEP ON RWY 30. TOLD HIM TO GET A FREQ UP QUICK AND FIND OUT WHAT WE WERE SUPPOSED TO DO. TWR, IN A RAISED VOICE, TOLD US TO VERIFY THAT WE WERE ALREADY ON 27L, AN ACTIVE RWY. I SAID THAT WE WERE, THAT WE HAD BEEN TOLD TO FOLLOW ACR B AND ASKED IF HE WANTED US TO FOLLOW HIM TO 27L OR 30. HE SAID HE HAD WANTED US TO FOLLOW ONLY TO 27L. I SAID IT WAS MY MISTAKE AND APOLOGIZED. HE CLRED US INTO POSITION AND HOLD. PERTINENT IS THE FACT THAT THIS WAS MY FIRST TRIP AS CAPT. MY F/O WAS ONLY ABOUT 2 WKS OUT OF TRAINING AS COPLT AFTER AT LEAST 6 MONTHS SITTING AT A F/E'S PANEL. ALSO, OUR AIRLINE JUST SWITCHED OPERATING PROCS AND CHECKLIST STYLE AND CONTENT. WITH THE CONFUSION OF TXWY ASSIGNMENT, CHANGE OF RWYS FROM WHAT WE HAD BEEN TOLD TO EXPECT AND THE USE OF NEW FLOWS AND CHECKLIST PROCS, MY ABILITY TO CONCENTRATE ON THE GND CTLR'S INSTRUCTIONS WAS IMPAIRED. THE F/O HAD EMPHASIZED THAT THE CTLR WANTED US TO FOLLOW ACR B AND I EXPECTED THAT HE WAS GOING TO THE SAME RWY WE WERE ASSIGNED. THE DISPLACED THRESHOLD OF 27L IS NOT REAL EVIDENT AS A RWY AND I HAD NOT NOTICED THE HOLD LINE THAT I EVIDENTLY CROSSED. I HAD CHECKED FOR TFC FROM MY LEFT TO REJOIN THE INNER AND LOOKED NEXT AT THE ACR B AND THEN AT MY ARPT DIAGRAM (10-9) AND REALIZED TOO LATE THAT ACR B HAD GONE TO RWY 30 AND I WAS HALF UPON WY 27L'S DISPLACED THRESHOLD. NO KNOWN CONFLICT RESULTED AND WHEN I ASKED THE CTLR IF WE HAD A PROBLEM, I BELIEVE HE SAID 'NEGATIVE'.

Data retrieved from NASA's ASRS site as of August 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.