Narrative:

Proceeding direct daxon on approximately heading of 190 degrees at altitude of 15000 ft when noticed conflicting traffic on TCASII scope at 20 mi approximately 1000 ft above descending. Relative position 11 O'clock. When other aircraft approximately 12 mi and 300 ft above our altitude, yellow warning followed by red warning and 'descend immediately' message. Having observed impending problem on TCASII and clearing area to right of aircraft, began descending right turn until TCASII indicated no further descent necessary. Stopped descent and, when alert ended, climbed back to 15000 ft and direct daxon. Prior to descent, unable to pick up conflicting traffic visually. When turn and descent began, notified ATC of actions being taken due to TCASII instructions. Turn and descent were not noticed by flight attendants since turn and descent anticipated. Lowest altitude reached was 14300 ft, and heading change of 30 degrees maximum. Not able to query ATC as to intentions of conflicting traffic prior to taking avoidance actions. Conditions were sparkling VFR with visibility unlimited, however, never saw conflicting traffic and assume traffic was a small aircraft. TCASII showed traffic never approached closer than approximately 6 or 7 mi at 10-11 O'clock position on TCASII screen. Frequency ATC was 124.75. I don't think that aircraft would have collided if descent and turn not made, but it would have been close. Love that TCASII!

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Original NASA ASRS Text

Title: POTENTIAL CONFLICT. THE FLC RECEIVES A TCASII RA ENRTE TO AN APCH AT SJU. THEY EVADE, BUT DO NOT SEE THE INTRUDER.

Narrative: PROCEEDING DIRECT DAXON ON APPROX HDG OF 190 DEGS AT ALT OF 15000 FT WHEN NOTICED CONFLICTING TFC ON TCASII SCOPE AT 20 MI APPROX 1000 FT ABOVE DSNDING. RELATIVE POS 11 O'CLOCK. WHEN OTHER ACFT APPROX 12 MI AND 300 FT ABOVE OUR ALT, YELLOW WARNING FOLLOWED BY RED WARNING AND 'DSND IMMEDIATELY' MESSAGE. HAVING OBSERVED IMPENDING PROB ON TCASII AND CLRING AREA TO R OF ACFT, BEGAN DSNDING R TURN UNTIL TCASII INDICATED NO FURTHER DSCNT NECESSARY. STOPPED DSCNT AND, WHEN ALERT ENDED, CLBED BACK TO 15000 FT AND DIRECT DAXON. PRIOR TO DSCNT, UNABLE TO PICK UP CONFLICTING TFC VISUALLY. WHEN TURN AND DSCNT BEGAN, NOTIFIED ATC OF ACTIONS BEING TAKEN DUE TO TCASII INSTRUCTIONS. TURN AND DSCNT WERE NOT NOTICED BY FLT ATTENDANTS SINCE TURN AND DSCNT ANTICIPATED. LOWEST ALT REACHED WAS 14300 FT, AND HDG CHANGE OF 30 DEGS MAX. NOT ABLE TO QUERY ATC AS TO INTENTIONS OF CONFLICTING TFC PRIOR TO TAKING AVOIDANCE ACTIONS. CONDITIONS WERE SPARKLING VFR WITH VISIBILITY UNLIMITED, HOWEVER, NEVER SAW CONFLICTING TFC AND ASSUME TFC WAS A SMALL ACFT. TCASII SHOWED TFC NEVER APCHED CLOSER THAN APPROX 6 OR 7 MI AT 10-11 O'CLOCK POS ON TCASII SCREEN. FREQ ATC WAS 124.75. I DON'T THINK THAT ACFT WOULD HAVE COLLIDED IF DSCNT AND TURN NOT MADE, BUT IT WOULD HAVE BEEN CLOSE. LOVE THAT TCASII!

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.