Date: 201807
Local time of day: 0601-1200
Location: PHX.Airport, AZ
Flight conditions: VMC
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B PHX
ATC / advisory: Tower PHX
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
Detector: Automation Aircraft RA; Automation Aircraft TA
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: On final approach to Runway 8 at PHX and configured for landing we passed about 1;600 AGL and got a TA (Traffic Advisory). Phoenix Tower had said nothing to us about any traffic and we were number one for landing. When the TA popped up it indicated that the traffic was about 10 o'clock and 300 feet below us and climbing. I immediately suspected a helicopter and started looking. We were on the glideslope for the ILS to Runway 8 and descending about 700 fpm. Within two seconds or so our TA became an RA (Resolution Advisory). I was the pilot monitoring and the RA commanded about a 2;000 fpm climb. I instructed the FO (First Officer) who was the PF (pilot flying) to respond to the RA he did so smoothly and correctly. As we climbed in response to the RA the target turned RED and indicated -200 feet and may have been -100 but I couldn't tell because the TCAS symbol for the target aircraft merged with our airplane symbol on the ND (Navigation Display). This action de-stabilized our approach badly so we performed a go-around. We were both incredulous when the Tower Controller said we were cleared to land ...'if we could still make it.' We climbed to 3;000 feet initially and then the Controller seemed to have some difficulty deciding what he wanted us to do. I had to ask him if he wanted us on the published missed approach or to fly a heading. He then said maintain 4;000 feet but no lateral guidance. He ultimately gave us a heading and said something like 'fly heading 080 at 4;000 climb to 6;000.' Things were happening fast and we were still trying to get cleaned up and set up for the return and I read back 'heading 080 maintaining 4000'. Fortunately; he handed us off to Approach Control who handled the rest of our return. Once we were finished responding to the situation and flying on downwind again. We never saw the helicopter but we did realize just how close we had come to a mid-air collision. I'm pretty sure there was a different controller handling the Tower frequency when we came back around. After landing and taxiing to the gate we asked the Ground Controller for a good phone number to call to discuss what had just happened. The person who answered the phone was not the same Controller who had handled our arrival. He immediately apologized and admitted fault for the incident. I asked about the aircraft and was told that it was a helicopter who was given the wrong transition and was flying over 300 ft higher than instructed. He was supposed to have been on the 35th Street transition and instead he flew the 'West' transition. The operating controller that caused this was relieved and receiving 'counseling' during my discussion with the person I spoke with on the phone.1. The operating controller had given us no warning at all.2. When the TA showed up it was mere seconds before it became an RA.3. We were on the approach descending to the runway on the ILS in visual conditions at about 700 fpm.4. The helicopter was climbing at an unknown rate toward us and definitely got within 200 feet of us and quite possibly less!The rest of the flight went normally and we had a routine landing. In conclusion; I would just like to emphasize just how close this was. Without the TCAS RA instructions and immediate procedural compliance; this incident would have ended in tragedy.This event would not have occurred at all if the helicopter had flown the proper transition through Class B airspace. Also; he should have flown his/her assigned altitude. What would have made this event a non-event is some notice from the Tower Controller who completely dropped the ball on this one.I honestly don't know what we could have done differently. The helicopter came out of nowhere; and ironically we never saw it at all. We had to rely on our TCAS equipment and our training to have the successful outcome that we did. FO did a fantastic job. Our crew and our passengers are all here because of his expeditious compliance with the RA instructions.




Synopsis: A321 Captain reported a near mid-air collision on approach to PHX airport.