Narrative:

Airborne at PM13 CDT. Under departure control level at 5000 ft, 250 KTS, heading 090 degrees. TCASII was operational in TA/RA with 10 mi range selected and several not threat targets displayed with altitude. Flight conditions were IMC with very little visibility. Yellow (TA) DOT suddenly 'popped' up on TCASII screen with aural warning. It was directly ahead of us and inside 2 1/2 mi range marker. DOT had no altitude which is why I believe we did not get an RA. We were closing rapidly and I started an evasive right turn and descent. The captain advised ATC that we had a TCASII alert and were turning right and descending. We cleared clouds at about 4000 ft heading about 180 degrees. TA position had stayed on our nose during initial part of turn. Now in clear, we saw no traffic as ATC said they had an mlt (off stewart, I presume) at our 9-10 O'clock. We climbed back to 5000 ft and turned to 090 degree heading with ATC concurrence. I don't believe we ever received altitude readout on TA. Our operations manual says not to respond to TA, only follow RA. However, it also states to visually scan (clear) the airspace you intend to maneuver into. You can't do this in the clouds. The TA situation in clouds is not covered. I find it difficult, if not impossible, to watch that yellow DOT converge with our position and not take action.

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Original NASA ASRS Text

Title: FLC OF ACR MLG ACFT RESPONDED TO TCASII TA RESULTING IN DEVIATING FROM ASSIGNED ALT.

Narrative: AIRBORNE AT PM13 CDT. UNDER DEP CTL LEVEL AT 5000 FT, 250 KTS, HDG 090 DEGS. TCASII WAS OPERATIONAL IN TA/RA WITH 10 MI RANGE SELECTED AND SEVERAL NOT THREAT TARGETS DISPLAYED WITH ALT. FLT CONDITIONS WERE IMC WITH VERY LITTLE VISIBILITY. YELLOW (TA) DOT SUDDENLY 'POPPED' UP ON TCASII SCREEN WITH AURAL WARNING. IT WAS DIRECTLY AHEAD OF US AND INSIDE 2 1/2 MI RANGE MARKER. DOT HAD NO ALT WHICH IS WHY I BELIEVE WE DID NOT GET AN RA. WE WERE CLOSING RAPIDLY AND I STARTED AN EVASIVE R TURN AND DSCNT. THE CAPT ADVISED ATC THAT WE HAD A TCASII ALERT AND WERE TURNING R AND DSNDING. WE CLRED CLOUDS AT ABOUT 4000 FT HDG ABOUT 180 DEGS. TA POS HAD STAYED ON OUR NOSE DURING INITIAL PART OF TURN. NOW IN CLR, WE SAW NO TFC AS ATC SAID THEY HAD AN MLT (OFF STEWART, I PRESUME) AT OUR 9-10 O'CLOCK. WE CLBED BACK TO 5000 FT AND TURNED TO 090 DEG HDG WITH ATC CONCURRENCE. I DON'T BELIEVE WE EVER RECEIVED ALT READOUT ON TA. OUR OPS MANUAL SAYS NOT TO RESPOND TO TA, ONLY FOLLOW RA. HOWEVER, IT ALSO STATES TO VISUALLY SCAN (CLR) THE AIRSPACE YOU INTEND TO MANEUVER INTO. YOU CAN'T DO THIS IN THE CLOUDS. THE TA SITUATION IN CLOUDS IS NOT COVERED. I FIND IT DIFFICULT, IF NOT IMPOSSIBLE, TO WATCH THAT YELLOW DOT CONVERGE WITH OUR POS AND NOT TAKE ACTION.

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.