Narrative:

After departing dfw international airport on regularly schedule passenger flight we were instructed to fly 060 degree heading at 3000 ft. Approximately 10 mi from dfw we were told to fly a 020 degree heading and climb to 4000 ft. At this time departure control was working a student pilot flying an small aircraft aircraft from addison airport. The small aircraft pilot was instructed to turn left to a 170 degree heading. He was level at 4000 ft but made a right turn instead which created the conflict between us and him. We had just been told to turn further left to a 340 degree heading and were climbing through 3600 ft when the ATC controller told us to immediately descend back to 3000 ft. The main reason I am submitting this report is that our aircraft is equipped with TCASII and during this event our display indicated the traffic as it should until (due to the deviation from instructions) the oncoming conflict brought the small aircraft display within the 2 mi circle on our display and we then received the basic 'traffic' alert which was still normal. Since we were climbing at approximately 1500- 1800 FPM this alert change rapidly to an RA. We were in the transition to a descent when the TCASII instructed us to climb and indicated a rate of 1800-2000 FPM. We were already indicating a descent on our vsi and the traffic display showed plus 200 ft, our highest altitude reached was 3800 ft when we received the RA. Since we were showing a descent, I instructed the first officer (who was flying) to continue the descent in spite of TCASII instructions. My quandary here of course is the difference in TCASII interpretation of resolving conflict as opposed to ours. The only answer I can see is that possibly the change from climb to descent was in progress when TCASII indicated the RA and its initial calculation was made before vsi indications changed enough for it to recalculate a new course of action. Otherwise it gave incorrect instructions. According to TRACON (dfw) radar display closest horizontal distance was 1.49 mi, and 200 ft vertically.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC OF ACR LTT ACFT DID NOT FOLLOW A TCASII RA SINCE THEY HAD THE OTHER ACFT IN SIGHT.

Narrative: AFTER DEPARTING DFW INTL ARPT ON REGULARLY SCHEDULE PAX FLT WE WERE INSTRUCTED TO FLY 060 DEG HDG AT 3000 FT. APPROX 10 MI FROM DFW WE WERE TOLD TO FLY A 020 DEG HDG AND CLB TO 4000 FT. AT THIS TIME DEP CTL WAS WORKING A STUDENT PLT FLYING AN SMA ACFT FROM ADDISON ARPT. THE SMA PLT WAS INSTRUCTED TO TURN L TO A 170 DEG HDG. HE WAS LEVEL AT 4000 FT BUT MADE A R TURN INSTEAD WHICH CREATED THE CONFLICT BTWN US AND HIM. WE HAD JUST BEEN TOLD TO TURN FURTHER L TO A 340 DEG HDG AND WERE CLBING THROUGH 3600 FT WHEN THE ATC CTLR TOLD US TO IMMEDIATELY DSND BACK TO 3000 FT. THE MAIN REASON I AM SUBMITTING THIS RPT IS THAT OUR ACFT IS EQUIPPED WITH TCASII AND DURING THIS EVENT OUR DISPLAY INDICATED THE TFC AS IT SHOULD UNTIL (DUE TO THE DEV FROM INSTRUCTIONS) THE ONCOMING CONFLICT BROUGHT THE SMA DISPLAY WITHIN THE 2 MI CIRCLE ON OUR DISPLAY AND WE THEN RECEIVED THE BASIC 'TFC' ALERT WHICH WAS STILL NORMAL. SINCE WE WERE CLBING AT APPROX 1500- 1800 FPM THIS ALERT CHANGE RAPIDLY TO AN RA. WE WERE IN THE TRANSITION TO A DSCNT WHEN THE TCASII INSTRUCTED US TO CLB AND INDICATED A RATE OF 1800-2000 FPM. WE WERE ALREADY INDICATING A DSCNT ON OUR VSI AND THE TFC DISPLAY SHOWED PLUS 200 FT, OUR HIGHEST ALT REACHED WAS 3800 FT WHEN WE RECEIVED THE RA. SINCE WE WERE SHOWING A DSCNT, I INSTRUCTED THE FO (WHO WAS FLYING) TO CONTINUE THE DSCNT IN SPITE OF TCASII INSTRUCTIONS. MY QUANDARY HERE OF COURSE IS THE DIFFERENCE IN TCASII INTERP OF RESOLVING CONFLICT AS OPPOSED TO OURS. THE ONLY ANSWER I CAN SEE IS THAT POSSIBLY THE CHANGE FROM CLB TO DSCNT WAS IN PROGRESS WHEN TCASII INDICATED THE RA AND ITS INITIAL CALCULATION WAS MADE BEFORE VSI INDICATIONS CHANGED ENOUGH FOR IT TO RECALCULATE A NEW COURSE OF ACTION. OTHERWISE IT GAVE INCORRECT INSTRUCTIONS. ACCORDING TO TRACON (DFW) RADAR DISPLAY CLOSEST HORIZ DISTANCE WAS 1.49 MI, AND 200 FT VERTICALLY.

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.