Date: 201812
Local time of day: 0601-1200
Location: DEN.Airport, CO
Flight conditions: VMC
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight phase: Final Approach
Airspace: Class B DEN
ATC / advisory: Tower DEN
Second aircraft: Bombardier/Canadair Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Conflict Airborne Conflict
Detector: Automation Aircraft RA
When detected: In-flight
Result: Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: TCAS RA [during] DEN visual Runway 16L.On a 220 heading to intercept; we got a traffic alert for traffic off our right and behind us. I do not recall DEN Tower telling us about traffic; but I could have missed them telling us about it. I was the Pilot Monitoring when a traffic alert went to an RA with descend command which the First Officer followed while we were looking for the traffic. The RA went to clear of conflict and back to descend command. We initiated another RA descent and again got clear of conflict. The TCAS Traffic symbol (now red) showed the conflicting traffic right on top of us with less than 300 ft vertical separation. We believed he must have been behind us and overtaking us for the parallel approach to [Runway] 16R. We couldn't see the traffic. I tried to notify the Approach Controller of the TCAS RA as we were approaching LEETS; the FAF for RWY 16L. There was so much traffic on the radio I couldn't communicate with the Approach Controller. At LEETS; I switched to Tower on my own and notified him of the TCAS RA to descend. We could see that the traffic was a CRJ passing us on final and going for [Runway] 16R. We landed visually without incident. We were to the left of localizer until clear of conflict the second time. The CRJ overtook us by at least 30 KTS on short final and from a higher altitude to landing before us. It appeared the CRJ did not attempt to climb during the TCAS event as we were descending with our RA. Once on Ramp frequency; my First Officer asked the pilot of [the other] flight if he got a TA. He responded 'lots of them.' He then asked if he got an RA with 'Climb' command and he said he did. He then asked if he followed it and he said 'I had you in sight I don't have to.' My First Officer explained to the pilot he was behind us and we couldn't see him so we had to descend. He responded that he 'wouldn't follow the RA command because he had us in sight.'


Second narrative: I understand that on closely spaced parallel approaches; we can turn to TA only but I could not get a good visual on the traffic; so I followed the descend command. Also; I was left of localizer when this happened and was not positive that the traffic was not overshooting his localizer. I had the map ring on its lowest selection and it was very difficult to tell his location or track.


Synopsis: A320 flight crew reported responding to a TCAS RA on approach to DEN.