Narrative:

We were descending into mia being controled and vectored by mia approach control. I believe we were descending out of 9000 ft for 5000 ft. Controller called traffic at 11000 ft I believe and close range. Within seconds we got a yellow TA followed very shortly by a red TCAS alert with a climb order. We climbed until clear of conflict. I then saw the airplane go directly underneath us 200 ft below. If not for the evasive action taken; it might have been a midair. Angle of closure would indicate that to me. TCAS worked like it was designed. We continued our assigned course to intercept the runway 27 ILS course. I then asked the tower just when he saw the traffic. He stated that it had been intermittent on his radar and that it just popped up. We continued approach to a normal landing. Our aircraft was headed in a generally northwest direction to intercept the localizer and the other aircraft was headed southeast. I believe the conflict occurred around 6500 ft as we descended from 11000 ft to 5000 ft. I wad descending at a rate of 1500 FPM.

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Original NASA ASRS Text

Title: B757 CAPT REPORTS TCAS RA AND NMAC WITH UNKNOWN ACFT AT 6500 FEET DURING VECTORS FOR ILS 27 AT MIA.

Narrative: WE WERE DSNDING INTO MIA BEING CTLED AND VECTORED BY MIA APCH CTL. I BELIEVE WE WERE DSNDING OUT OF 9000 FT FOR 5000 FT. CTLR CALLED TFC AT 11000 FT I BELIEVE AND CLOSE RANGE. WITHIN SECONDS WE GOT A YELLOW TA FOLLOWED VERY SHORTLY BY A RED TCAS ALERT WITH A CLB ORDER. WE CLBED UNTIL CLR OF CONFLICT. I THEN SAW THE AIRPLANE GO DIRECTLY UNDERNEATH US 200 FT BELOW. IF NOT FOR THE EVASIVE ACTION TAKEN; IT MIGHT HAVE BEEN A MIDAIR. ANGLE OF CLOSURE WOULD INDICATE THAT TO ME. TCAS WORKED LIKE IT WAS DESIGNED. WE CONTINUED OUR ASSIGNED COURSE TO INTERCEPT THE RWY 27 ILS COURSE. I THEN ASKED THE TWR JUST WHEN HE SAW THE TFC. HE STATED THAT IT HAD BEEN INTERMITTENT ON HIS RADAR AND THAT IT JUST POPPED UP. WE CONTINUED APCH TO A NORMAL LNDG. OUR ACFT WAS HEADED IN A GENERALLY NW DIRECTION TO INTERCEPT THE LOC AND THE OTHER ACFT WAS HEADED SE. I BELIEVE THE CONFLICT OCCURRED AROUND 6500 FT AS WE DSNDED FROM 11000 FT TO 5000 FT. I WAD DSNDING AT A RATE OF 1500 FPM.

Data retrieved from NASA's ASRS site as of May 2009 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.