Narrative:

We were cleared to taxi out to runway 9L (no specific taxi route given). During taxi out our operations was slow providing the weight and balance numbers for our flight over the ACARS. The first officer called to operations while (approaching the runway) to obtain the numbers for takeoff while I remained with ground control. During this time I was mentally calculating the takeoff weight for a check with the operations numbers as I have previously received incorrect numbers at this station. In the meantime ground changed our takeoff runway to 12 and switched us to tower which I acknowledged and switched (first officer still on operations frequency). The first officer got the numbers and the checklists completed as we were cleared for takeoff. (Still a way out from the runways but rapidly approaching them.) I questioned the gross takeoff weight and asked the first officer to radio operations and confirm it, which he did. The runways at mia are thus. While we were cleared for takeoff on 12 I still had runway 9L in mind from the initial clearance and actually began to pull onto 9L when tower called us and said to make a left as that was 9L and we were cleared for 12 (there was an aircraft on about a 3 mi final for 9L). I then made the left and made the takeoff on 12 but did enter the runway 9L slightly before being called by tower. All this took place in less time than it takes to tell. One obvious problem was the weight numbers distraction. Another was the physical layout of the runway at mia and the usual limited markings identing the runways. Of course being cleared for both runways did not help. Solution: stop distrs, or stop until they are cleared up -- 2 better runway markings.

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Original NASA ASRS Text

Title: ACR HAS RWY CHANGE ON TAXI AT MIA WHILE TRYING TO GET WT AND BAL INFO. TURNS TOWARD WRONG RWY, GND CTLR CATCHES ERROR.

Narrative: WE WERE CLRED TO TAXI OUT TO RWY 9L (NO SPECIFIC TAXI RTE GIVEN). DURING TAXI OUT OUR OPS WAS SLOW PROVIDING THE WT AND BAL NUMBERS FOR OUR FLT OVER THE ACARS. THE FO CALLED TO OPS WHILE (APCHING THE RWY) TO OBTAIN THE NUMBERS FOR TKOF WHILE I REMAINED WITH GND CTL. DURING THIS TIME I WAS MENTALLY CALCULATING THE TKOF WT FOR A CHK WITH THE OPS NUMBERS AS I HAVE PREVIOUSLY RECEIVED INCORRECT NUMBERS AT THIS STATION. IN THE MEANTIME GND CHANGED OUR TKOF RWY TO 12 AND SWITCHED US TO TWR WHICH I ACKNOWLEDGED AND SWITCHED (FO STILL ON OPS FREQ). THE FO GOT THE NUMBERS AND THE CHKLISTS COMPLETED AS WE WERE CLRED FOR TKOF. (STILL A WAY OUT FROM THE RWYS BUT RAPIDLY APCHING THEM.) I QUESTIONED THE GROSS TKOF WT AND ASKED THE FO TO RADIO OPS AND CONFIRM IT, WHICH HE DID. THE RWYS AT MIA ARE THUS. WHILE WE WERE CLRED FOR TKOF ON 12 I STILL HAD RWY 9L IN MIND FROM THE INITIAL CLRNC AND ACTUALLY BEGAN TO PULL ONTO 9L WHEN TWR CALLED US AND SAID TO MAKE A L AS THAT WAS 9L AND WE WERE CLRED FOR 12 (THERE WAS AN ACFT ON ABOUT A 3 MI FINAL FOR 9L). I THEN MADE THE L AND MADE THE TKOF ON 12 BUT DID ENTER THE RWY 9L SLIGHTLY BEFORE BEING CALLED BY TWR. ALL THIS TOOK PLACE IN LESS TIME THAN IT TAKES TO TELL. ONE OBVIOUS PROBLEM WAS THE WT NUMBERS DISTR. ANOTHER WAS THE PHYSICAL LAYOUT OF THE RWY AT MIA AND THE USUAL LIMITED MARKINGS IDENTING THE RWYS. OF COURSE BEING CLRED FOR BOTH RWYS DID NOT HELP. SOLUTION: STOP DISTRS, OR STOP UNTIL THEY ARE CLRED UP -- 2 BETTER RWY MARKINGS.

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.