Narrative:

While descending to 16;000 ft from previously assigned altitude; I was giving my announcement to the passengers at the time. After I finished my announcement; I tuned back to communication 1 and heard captain mentioning incoming traffic while we were in IMC. We leveled at 16;000 ft; approximately a moment later; we spotted traffic in our TCAS and it showed the target coming at us while climbing; roughly -15 on the TCAS and decreasing. Captain said they should be level at 15;000 ft. As we were coming closer to the target; it didn't stop at 15;000; and then TCAS changed from blue to yellow and was showing -8.at that point; captain immediately had his hands on the controls and was ready to avoid the traffic while we both were monitoring the TCAS. Seconds later; TCAS showed target minus 4 in red that's when we received a TCAS RA; 'climb'. Captain disengaged the autopilot and climbed as instructed by TCAS. I immediately notified ATC; 'TCAS climb'; but never got a response nor was given any additional information regarding the traffic. We climbed to FL180 where we were given the clear of conflict from TCAS. About my 4th call to ATC; they finally acknowledged my call; and I told them we were at FL180 and that we could go back down to 16;000 ft. They assigned us 11;000 ft; then 10;000 ft. I asked them what happened; and they gave us a number to call if we wanted a detailed explanation of what happened. We landed at [our destination]; captain called the number and we were told that the other aircraft didn't level off at his assigned altitude nor did he followed his TCAS RA.it was a near miss; roughly about 400 ft of vertical separation. Without the TCAS; the result would have been catastrophic.

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Original NASA ASRS Text

Title: EMB-145XR crew climbed above assigned altitude while responding to TCAS RA.

Narrative: While descending to 16;000 FT from previously assigned altitude; I was giving my announcement to the passengers at the time. After I finished my announcement; I tuned back to COM 1 and heard Captain mentioning incoming traffic while we were in IMC. We leveled at 16;000 FT; approximately a moment later; we spotted traffic in our TCAS and it showed the target coming at us while climbing; roughly -15 on the TCAS and decreasing. Captain said they should be level at 15;000 FT. As we were coming closer to the target; it didn't stop at 15;000; and then TCAS changed from blue to yellow and was showing -8.At that point; Captain immediately had his hands on the controls and was ready to avoid the traffic while we both were monitoring the TCAS. Seconds later; TCAS showed target minus 4 in red that's when we received a TCAS RA; 'Climb'. Captain disengaged the autopilot and climbed as instructed by TCAS. I immediately notified ATC; 'TCAS Climb'; but never got a response nor was given any additional information regarding the traffic. We climbed to FL180 where we were given the clear of conflict from TCAS. About my 4th call to ATC; they finally acknowledged my call; and I told them we were at FL180 and that we could go back down to 16;000 FT. They assigned us 11;000 FT; then 10;000 FT. I asked them what happened; and they gave us a number to call if we wanted a detailed explanation of what happened. We landed at [our destination]; Captain called the number and we were told that the other aircraft didn't level off at his assigned altitude nor did he followed his TCAS RA.It was a near miss; roughly about 400 FT of vertical separation. Without the TCAS; the result would have been catastrophic.

Data retrieved from NASA's ASRS site as of July 2013 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.