Narrative:

Cleared onto runway 9L at mia behind A-300. Wind 070 degrees at 7 KTS. Started clock as A-300 started takeoff roll. At 1 min 5 seconds tower cleared us for takeoff. TCASII showed A-300 at 3 1/2 NM and we commented it was only 1 min. At 1 min 15 seconds tower supervisor came on radio and said if you need 2 mins, we need to know beforehand. At this point, TCASII showed 4 NM. We acknowledged takeoff clearance and started takeoff roll at XX35 with TCASII showing 4 1/2 NM. I know TCASII is not supposed to be used in this manner, but it seems pretty accurate and there is no A-300 in the world that can make 5 NM from a standing start in 1 min 5 seconds. Shortly before this, a flight had balked at non-standard separation. I realize tower has to move aircraft as quickly as possible, but heavy aircraft separation in light wind conditions should never be compromised.

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Original NASA ASRS Text

Title: WAKE TURB SEPARATION.

Narrative: CLRED ONTO RWY 9L AT MIA BEHIND A-300. WIND 070 DEGS AT 7 KTS. STARTED CLOCK AS A-300 STARTED TKOF ROLL. AT 1 MIN 5 SECONDS TWR CLRED US FOR TKOF. TCASII SHOWED A-300 AT 3 1/2 NM AND WE COMMENTED IT WAS ONLY 1 MIN. AT 1 MIN 15 SECONDS TWR SUPVR CAME ON RADIO AND SAID IF YOU NEED 2 MINS, WE NEED TO KNOW BEFOREHAND. AT THIS POINT, TCASII SHOWED 4 NM. WE ACKNOWLEDGED TKOF CLRNC AND STARTED TKOF ROLL AT XX35 WITH TCASII SHOWING 4 1/2 NM. I KNOW TCASII IS NOT SUPPOSED TO BE USED IN THIS MANNER, BUT IT SEEMS PRETTY ACCURATE AND THERE IS NO A-300 IN THE WORLD THAT CAN MAKE 5 NM FROM A STANDING START IN 1 MIN 5 SECONDS. SHORTLY BEFORE THIS, A FLT HAD BALKED AT NON-STANDARD SEPARATION. I REALIZE TWR HAS TO MOVE ACFT AS QUICKLY AS POSSIBLE, BUT HVY ACFT SEPARATION IN LIGHT WIND CONDITIONS SHOULD NEVER BE COMPROMISED.

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.