Narrative:

On the atl VARNM2 departure; we were just south of varnm; and told to level at 15;000 feet. ATC (atlanta departure) advises that traffic was at 12 o'clock; 12 miles at 15;500 feet. We leveled off at 15;000 feet and looked for traffic. The traffic appeared in the TCAS with a TCAS TA at 500 feet above; when at around 10 to 11 miles. Then the traffic advisory turned to a TCAS RA as the traffic showed 400 feet above; then 300 feet above within less than 10 miles. I disconnected the autopilot and started a descent. The TCAS RA resolution was to descend; and we did so. The traffic passed overhead as we descended to 14;300 feet; and the TCAS showed them now at 600 to 700 feet above us; when we started leveling at 14;300. The TCAS RA went away; and the first officer (first officer) advised ATC that we had a TCAS RA and had to descend to avoid conflict. We relayed altitudes to the controller; our altitude as well as what proximate altitude the TCAS showed the conflicting traffic at. Once clear; we climbed back to 15;000 feet and resumed the flight as normal.conflicting traffic descended into our altitude. The pilot that we conflicted with asked ATC what altitude he was showing him at on radar; and stated that he thought he was at 15;500 feet.my crew and I did as we were trained and instructed to do when presented with a TCAS RA. The controller let us pass each other on a head in diverging course; with 500 feet separation; but the conflicting aircraft appeared to not be maintaining altitude as they descended into our altitude. We escaped into a descent to avoid impact.

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Original NASA ASRS Text

Title: EMB-175 Captain reported responding to a TCAS Resolution Advisory departing ATL.

Narrative: On the ATL VARNM2 departure; we were just south of VARNM; and told to level at 15;000 feet. ATC (Atlanta Departure) advises that traffic was at 12 o'clock; 12 miles at 15;500 feet. We leveled off at 15;000 feet and looked for traffic. The traffic appeared in the TCAS with a TCAS TA at 500 feet above; when at around 10 to 11 miles. Then the traffic advisory turned to a TCAS RA as the traffic showed 400 feet above; then 300 feet above within less than 10 miles. I disconnected the autopilot and started a descent. The TCAS RA resolution was to descend; and we did so. The traffic passed overhead as we descended to 14;300 feet; and the TCAS showed them now at 600 to 700 feet above us; when we started leveling at 14;300. The TCAS RA went away; and the FO (First Officer) advised ATC that we had a TCAS RA and had to descend to avoid conflict. We relayed altitudes to the Controller; our altitude as well as what proximate altitude the TCAS showed the conflicting traffic at. Once clear; we climbed back to 15;000 feet and resumed the flight as normal.Conflicting traffic descended into our altitude. The pilot that we conflicted with asked ATC what altitude he was showing him at on radar; and stated that he thought he was at 15;500 feet.My crew and I did as we were trained and instructed to do when presented with a TCAS RA. The Controller let us pass each other on a head in diverging course; with 500 feet separation; but the conflicting aircraft appeared to not be maintaining altitude as they descended into our altitude. We escaped into a descent to avoid impact.

Data retrieved from NASA's ASRS site 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.