Narrative:

ATC facility: mia tower. Location: mia. We were cleared into position and hold on runway 9L. As I started my taxi into position, we got the clearance to take off. I aligned the aircraft with the centerline and set takeoff power. I rotated/lifted off on speed to a maximum pitch of 20 degrees. Shortly after liftoff (the 300-400 ft), we had a TA. I looked at the TCASII 5 mi range and saw a traffic at 11 O'clock position going west to southwest less than 2 mi and 200 ft above. I reduced the power slightly and lowered the nose. The traffic passed behind us, same altitude or slightly below us, less than 1 mi behind us. We were assigned a new heading. The first officer prompted the tower for a frequency change. I asked the tower if he was aware of the traffic that came close. He told no traffic was observed and that departure was looking for us. We changed to departure frequency, and were advised to make a left turn for traffic. We complied, however, I reduced the rate of turn to avoid a twring cloud in our path. Both the tower and departure did not observe the traffic and advised that there was no conflict observed. What led to the traffic conflict, in my judgement, is our light takeoff weight and the high performance of B757. We were airborne at no time and probably were above the profile, a standard to profile.

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Original NASA ASRS Text

Title: AFTER TKOF MIA, A B757 CREW RECEIVED A TCASII TA ON TFC AT 11 O'CLOCK POS AND 2 MI, APPROX 600-800 FT. TFC UNKNOWN TO ATC.

Narrative: ATC FACILITY: MIA TWR. LOCATION: MIA. WE WERE CLRED INTO POS AND HOLD ON RWY 9L. AS I STARTED MY TAXI INTO POS, WE GOT THE CLRNC TO TAKE OFF. I ALIGNED THE ACFT WITH THE CTRLINE AND SET TKOF PWR. I ROTATED/LIFTED OFF ON SPD TO A MAX PITCH OF 20 DEGS. SHORTLY AFTER LIFTOFF (THE 300-400 FT), WE HAD A TA. I LOOKED AT THE TCASII 5 MI RANGE AND SAW A TFC AT 11 O'CLOCK POS GOING W TO SW LESS THAN 2 MI AND 200 FT ABOVE. I REDUCED THE PWR SLIGHTLY AND LOWERED THE NOSE. THE TFC PASSED BEHIND US, SAME ALT OR SLIGHTLY BELOW US, LESS THAN 1 MI BEHIND US. WE WERE ASSIGNED A NEW HDG. THE FO PROMPTED THE TWR FOR A FREQ CHANGE. I ASKED THE TWR IF HE WAS AWARE OF THE TFC THAT CAME CLOSE. HE TOLD NO TFC WAS OBSERVED AND THAT DEP WAS LOOKING FOR US. WE CHANGED TO DEP FREQ, AND WERE ADVISED TO MAKE A L TURN FOR TFC. WE COMPLIED, HOWEVER, I REDUCED THE RATE OF TURN TO AVOID A TWRING CLOUD IN OUR PATH. BOTH THE TWR AND DEP DID NOT OBSERVE THE TFC AND ADVISED THAT THERE WAS NO CONFLICT OBSERVED. WHAT LED TO THE TFC CONFLICT, IN MY JUDGEMENT, IS OUR LIGHT TKOF WT AND THE HIGH PERFORMANCE OF B757. WE WERE AIRBORNE AT NO TIME AND PROBABLY WERE ABOVE THE PROFILE, A STANDARD TO PROFILE.

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.