Narrative:

After starting 1 engine, we requested taxi clearance and were instructed by ground to taxi to runway 9L. While taxiing out ground pointed out another airliner on an adjacent taxiway which we were told was our sequence. While approaching the runways we started the second engine and the first officer contacted operations on the #2 radio to get our weight and balance information. Just as these tasks were complete tower instructed us to move to the right on the large taxi area so the sequence aircraft (the one departing ahead of us) could move into position on runway 12 for takeoff. During the period leading up to our takeoff several aircraft had departed on runway 12. After our sequence aircraft departed we were instructed to taxi into position and hold. We taxied onto runway 12 thinking that was our assigned runway. When we were in position on runway 12, tower informed us our assigned runway was 9L. However, we were then told to depart on runway 12 and turn to a 90 degree heading which we did. The first officer believes tower's clearance into position and hold did not include a runway assignment. After seeing all the previous aircraft, including the one we were to follow takeoff on 12, I simply got it into my head we were also to use 12, and forgot about the original 9L assignment from ground. Lesson when ground specifies a runway at the first taxi clearance think only of that runway until tower of ground assigns another. Callback conversation with reporter revealed the following information. Says he watched as all the previous aircraft takeoff on runway 12 and got mindset that 12 was the runway he should also use. Second engine start occurred as they approached the runup pad which serves both runways 12 and 9L. Flight crew was busy but not overloaded. Runway incursion did not cause any traffic conflict.

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Original NASA ASRS Text

Title: ACR TAXIED ONTO WRONG RWY AT MIA. UNAUTH RWY ENTRY.

Narrative: AFTER STARTING 1 ENG, WE REQUESTED TAXI CLRNC AND WERE INSTRUCTED BY GND TO TAXI TO RWY 9L. WHILE TAXIING OUT GND POINTED OUT ANOTHER AIRLINER ON AN ADJACENT TAXIWAY WHICH WE WERE TOLD WAS OUR SEQUENCE. WHILE APCHING THE RWYS WE STARTED THE SECOND ENG AND THE FO CONTACTED OPS ON THE #2 RADIO TO GET OUR WT AND BAL INFO. JUST AS THESE TASKS WERE COMPLETE TWR INSTRUCTED US TO MOVE TO THE R ON THE LARGE TAXI AREA SO THE SEQUENCE ACFT (THE ONE DEPARTING AHEAD OF US) COULD MOVE INTO POS ON RWY 12 FOR TKOF. DURING THE PERIOD LEADING UP TO OUR TKOF SEVERAL ACFT HAD DEPARTED ON RWY 12. AFTER OUR SEQUENCE ACFT DEPARTED WE WERE INSTRUCTED TO TAXI INTO POS AND HOLD. WE TAXIED ONTO RWY 12 THINKING THAT WAS OUR ASSIGNED RWY. WHEN WE WERE IN POS ON RWY 12, TWR INFORMED US OUR ASSIGNED RWY WAS 9L. HOWEVER, WE WERE THEN TOLD TO DEPART ON RWY 12 AND TURN TO A 90 DEG HDG WHICH WE DID. THE FO BELIEVES TWR'S CLRNC INTO POS AND HOLD DID NOT INCLUDE A RWY ASSIGNMENT. AFTER SEEING ALL THE PREVIOUS ACFT, INCLUDING THE ONE WE WERE TO FOLLOW TKOF ON 12, I SIMPLY GOT IT INTO MY HEAD WE WERE ALSO TO USE 12, AND FORGOT ABOUT THE ORIGINAL 9L ASSIGNMENT FROM GND. LESSON WHEN GND SPECIFIES A RWY AT THE FIRST TAXI CLRNC THINK ONLY OF THAT RWY UNTIL TWR OF GND ASSIGNS ANOTHER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. SAYS HE WATCHED AS ALL THE PREVIOUS ACFT TKOF ON RWY 12 AND GOT MINDSET THAT 12 WAS THE RWY HE SHOULD ALSO USE. SECOND ENG START OCCURRED AS THEY APCHED THE RUNUP PAD WHICH SERVES BOTH RWYS 12 AND 9L. FLC WAS BUSY BUT NOT OVERLOADED. RWY INCURSION DID NOT CAUSE ANY TFC CONFLICT.

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.