Air carrier flight crews of separate flights reported conflicting with each other during approach requiring evasive action. One of the crews reported task saturation and communication issues with ATC resulted in a track heading deviation which caused the NMAC.
Synopsis
Air carrier flight crews of separate flights reported conflicting with each other during approach requiring evasive action. One of the crews reported task saturation and communication issues with ATC resulted in a track heading deviation which caused the NMAC.
Narrative
We were on approach to [Runway] XXL. Weather in the area consisted many areas of moderate to heavy precipitation. Approach controllers seemed overworked as assigned speed was not gradual reduction but rather assigned to slow from 190 to 170 to 150 in a very short period of time. Our speed control was good and we were configured and on speed prior to ZZZZZ [intersection]. While on the approach I started to see a bright light appear in the FO side window. Visibility from the rain was obscuring the image but it was evident that it was another aircraft. I queried my FO as to what they were doing and told him I was getting uncomfortable with what was happening. I got to a point where I was no longer willing to accept what was happening and started to move toward a defensive position. I decided to turn off the autopilot and turn away from the traffic at the same time ATC started giving commands to turn left immediately. I turned away from the traffic aggressively and received the bank angle warning along with the RA call. I continued to scan from the PFD back to the other aircraft to make sure we were getting away from them. I could tell that we were below and to the left of him and that he appeared to be turning away from us. Although the visibility was low; it was evident that the interfering aircraft was an air carrier. Glancing back at the PFD I saw that escape guidance was displayed. It went away almost as soon as I realized it was there. I do remember it showing to not climb. Once the conflict was clear we queried ATC for a heading and altitude. Once the new clearance was received; I pushed the GA paddles and we executed the go-around procedure. We were sequenced back in to the arrivals and eventually landed without further incident. I called the duty officer to report the near mid air collision. Dispatch took the information and said she would reach out if any further information was required. Dispatch asked if we were alright to continue. I assured them that we were; but would like to recognize how important I thought it was that she asked.Cause - This event was caused by an aircraft transgressing our flight path. In my opinion the transgressing crew and ATC agency had a breakdown. Suggestions - Flight crews need to continuously monitor traffic around them especially during low IMC approaches. ATC needs to be vigilant when they are dealing with this much traffic during low IMC approaches and prevent incursions of this nature.
Second reporter narrative
Approach [was] uneventful until inside FAF (ZZZZZ [Intersection]). Pilot flying noticed aircraft on ILS [Runway] XXR drifting towards us. At 1;500 AGL PF disconnected autopilot and turned west to avoid collision. Shortly after; Tower directed immediate left turn followed by a TCAS RA. At last recollection TCAS showed other aircraft 200 feet above. We were in between cloud decks and saw aircraft visually. My estimate is we were 300 feet lateral separation. After initial avoidance measures we conducted standard missed approach and took vectors for another ILS [Runway] XXL and landed uneventfully.Cause - Other aircraft deviated from their approach corridor creating conditions for potential mid-air collision.Suggestions - Nothing on our part. Not sure the situation in the other aircraft but I would say better monitoring and adherence of flight path.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.