Narrative:

While descending and being vectored on a right downwind, prior to passing abeam the field, sju approach control advised we would follow a widebody transport X on a 15-mi final for a lagoon visibility to runway 08 at sju. When we were an estimated 4-5 mi past the airport, still descending, the controller said the traffic we were to follow was at 2 O'clock. Both the first officer (who was flying) and F/east called the traffic in sight and I spotted an aircraft at that location. I reported the traffic in sight. We were cleared for the lagoon visibility to runway 08, to follow the widebody transport X who's gndspd was 190 KTS, and cautioned of possible wake turbulence. I checked our indicated airspeed, which was about 120 KTS, and decided there would be no speed problem. The first officer turned to follow the traffic. On base leg, the controller asked if we still had the traffic in sight, and again said his speed was 190 KTS. The aircraft we were watching was to our right on final approach, and I reported that we still had the traffic in sight. Approximately 2/3 of the way through our turn to final, I spotted a widebody transport in our 8 O'clock position, low. I estimate his position to be approximately 1/2 mi distance and 300-500' below our aircraft. I immediately told the first officer to level off (we were about 2200') and continue turning right, which he did. I then told the controller we had another aircraft to our left and would continue our right turn. He acknowledged, gave us a heading to fly and cleared us to climb to 2500'. (The aircraft we had reported as being in sight, and had been spacing ourselves behind, had just touched down at that time.) we were then vectored through an elongated 360 degree turn back to final and completed the approach and landing west/O incident. Later, in operations, I met the crew of the aircraft we had attempted to follow and learned it had been a different widebody transport.

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Original NASA ASRS Text

Title: FLT CREW OF LGT CLEARED TO FOLLOW A WDB ON APCH TO SJU IDENTIFIED AND MOMENTARILY FOLLOWED THE WRONG ACFT.

Narrative: WHILE DSNDING AND BEING VECTORED ON A RIGHT DOWNWIND, PRIOR TO PASSING ABEAM THE FIELD, SJU APCH CTL ADVISED WE WOULD FOLLOW A WDB X ON A 15-MI FINAL FOR A LAGOON VIS TO RWY 08 AT SJU. WHEN WE WERE AN ESTIMATED 4-5 MI PAST THE ARPT, STILL DSNDING, THE CTLR SAID THE TFC WE WERE TO FOLLOW WAS AT 2 O'CLOCK. BOTH THE F/O (WHO WAS FLYING) AND F/E CALLED THE TFC IN SIGHT AND I SPOTTED AN ACFT AT THAT LOCATION. I RPTED THE TFC IN SIGHT. WE WERE CLRED FOR THE LAGOON VIS TO RWY 08, TO FOLLOW THE WDB X WHO'S GNDSPD WAS 190 KTS, AND CAUTIONED OF POSSIBLE WAKE TURB. I CHKED OUR INDICATED AIRSPD, WHICH WAS ABOUT 120 KTS, AND DECIDED THERE WOULD BE NO SPD PROB. THE F/O TURNED TO FOLLOW THE TFC. ON BASE LEG, THE CTLR ASKED IF WE STILL HAD THE TFC IN SIGHT, AND AGAIN SAID HIS SPD WAS 190 KTS. THE ACFT WE WERE WATCHING WAS TO OUR RIGHT ON FINAL APCH, AND I RPTED THAT WE STILL HAD THE TFC IN SIGHT. APPROX 2/3 OF THE WAY THROUGH OUR TURN TO FINAL, I SPOTTED A WDB IN OUR 8 O'CLOCK POS, LOW. I ESTIMATE HIS POS TO BE APPROX 1/2 MI DISTANCE AND 300-500' BELOW OUR ACFT. I IMMEDIATELY TOLD THE F/O TO LEVEL OFF (WE WERE ABOUT 2200') AND CONTINUE TURNING RIGHT, WHICH HE DID. I THEN TOLD THE CTLR WE HAD ANOTHER ACFT TO OUR LEFT AND WOULD CONTINUE OUR RIGHT TURN. HE ACKNOWLEDGED, GAVE US A HDG TO FLY AND CLRED US TO CLB TO 2500'. (THE ACFT WE HAD RPTED AS BEING IN SIGHT, AND HAD BEEN SPACING OURSELVES BEHIND, HAD JUST TOUCHED DOWN AT THAT TIME.) WE WERE THEN VECTORED THROUGH AN ELONGATED 360 DEG TURN BACK TO FINAL AND COMPLETED THE APCH AND LNDG W/O INCIDENT. LATER, IN OPS, I MET THE CREW OF THE ACFT WE HAD ATTEMPTED TO FOLLOW AND LEARNED IT HAD BEEN A DIFFERENT WDB.

Data retrieved from NASA's ASRS site as of August 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.