Narrative:

M flight nov/xx/94 iad-den, aircraft T, a DC10-10 in cruise FL280, approximately 65 mi southwest of stl VOR on J110 wbound. At XA18Z we got a 'traffic, traffic' TA on TCASII. The target was 12 O'clock on TCASII, opposite direction, showing 28900 ft descending. The so located the traffic visually at 12 O'clock. TCASII showed the distance at 15-18 mi. The TA was followed shortly by a 'descend, descend now' RA. I started descent following guidance on the vsi, and had the first officer advise ATC that we are descending in response to an RA. The controller's response was approximately 'don't descend, turn right to heading 360 degrees.' right after that he instructed us to tighten up the turn. By this time the RA changed to 'monitor vertical speed' and our altitude was about 27600 ft. The first officer observed the conflicting traffic's altitude on TCASII at 28400 ft still descending, then appeared to start climbing. I observed the traffic passing just to our left visually while on TCASII the first officer observed the target and altitude readout pass over and just to the left of the center mark on the TCASII screen, 20 mi scale. ATC cleared us to FL270 for a while, then back to FL280, direct to bum VOR and on course. I advised ATC at that time that we were filing an near midair collision report. TCASII may have saved 2 more.

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Original NASA ASRS Text

Title: LOSS OF TFC SEPARATION.

Narrative: M FLT NOV/XX/94 IAD-DEN, ACFT T, A DC10-10 IN CRUISE FL280, APPROX 65 MI SW OF STL VOR ON J110 WBOUND. AT XA18Z WE GOT A 'TFC, TFC' TA ON TCASII. THE TARGET WAS 12 O'CLOCK ON TCASII, OPPOSITE DIRECTION, SHOWING 28900 FT DSNDING. THE SO LOCATED THE TFC VISUALLY AT 12 O'CLOCK. TCASII SHOWED THE DISTANCE AT 15-18 MI. THE TA WAS FOLLOWED SHORTLY BY A 'DSND, DSND NOW' RA. I STARTED DSCNT FOLLOWING GUIDANCE ON THE VSI, AND HAD THE FO ADVISE ATC THAT WE ARE DSNDING IN RESPONSE TO AN RA. THE CTLR'S RESPONSE WAS APPROX 'DON'T DSND, TURN R TO HDG 360 DEGS.' RIGHT AFTER THAT HE INSTRUCTED US TO TIGHTEN UP THE TURN. BY THIS TIME THE RA CHANGED TO 'MONITOR VERT SPD' AND OUR ALT WAS ABOUT 27600 FT. THE FO OBSERVED THE CONFLICTING TFC'S ALT ON TCASII AT 28400 FT STILL DSNDING, THEN APPEARED TO START CLBING. I OBSERVED THE TFC PASSING JUST TO OUR L VISUALLY WHILE ON TCASII THE FO OBSERVED THE TARGET AND ALT READOUT PASS OVER AND JUST TO THE L OF THE CTR MARK ON THE TCASII SCREEN, 20 MI SCALE. ATC CLRED US TO FL270 FOR A WHILE, THEN BACK TO FL280, DIRECT TO BUM VOR AND ON COURSE. I ADVISED ATC AT THAT TIME THAT WE WERE FILING AN NMAC RPT. TCASII MAY HAVE SAVED 2 MORE.

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.