Date: 202011
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E ZZZ
ATC / advisory: CTAF ZZZ; TRACON ZZZ
Second aircraft: Helicopter
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure; Situational Awareness; Communication Breakdown; Confusion; Distraction
Second reporter function: Pilot Flying; First Officer
Anomaly: ATC Issue All Types; Conflict NMAC
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Airport; Environment - Non Weather Related; Human Factors; Staffing
Primary problem: Environment - Non Weather Related

Narrative: While the FO was flying the RNAV RNP Y approach to the runway at ZZZ with the Tower out of operation; we were cleared for the approach by ZZZ Approach following the report from the previous aircraft that they were clear and canceling IFR. We were then told to switch over to CTAF frequency. Upon making my first report on CTAF; and in the vicinity of ZZZZZ [Intersection]; we got a TCAS traffic alert. Neither the FO; nor I were able to locate the traffic; we then got an RA to reduce our decent rate. We complied with the RA and the TCAS advised us that we were clear of conflict. It appeared that we were within 100 feet of what turned out to be a helicopter that was beneath us. The remainder of the approach and landing were normal. Upon landing we reported to ZZZ Approach that we had gotten an RA on approach. We also talked to the helicopter and he said he had us on TCAS. I think that meant he had gotten an RA also.Tower being closed when it was supposed to be open is a cause for this event. ZZZ Approach not advising about traffic in the area when cleared for the approach is a contributor. The helicopter flying through an approach corridor when active approaches are going on is a contributor.Why is the Tower not operating at XA:00 at night?? Why are we flying to places that don't have an operating Tower? Why didn't ZZZ Approach know anything about the helicopter? What was the helicopter doing in that area? We were one of several aircraft in a line for that very same approach and were exactly where we were supposed to be when we got the RA. To think we were 100 feet away from a major aircraft incident doesn't set well with me. The ZZZ approach and landing is challenging enough with terrain; nighttime etc. We are a large commercial airline operation. We are not some small aircraft out for a weekend joy ride at our local FBO. We need to have all the available tools working for us. We shouldn't have to be making calls on CTAF; figuring out our own traffic separation; clicking the mic to get the runway lights to come on etc.; etc.


Second narrative: RA on approach. While flying the RNAV RNP Y Runway XXL; in night VFR conditions; received an RA in the vicinity of ZZZZZ [Intersection].Approach control cleared the flight to fly the approach lateral path; but maintain altitude; ATC provided step downs to keep us on profile while awaiting IFR cancellation from preceding aircraft.Received approach clearance in the vicinity of ZZZZZ1; advised by Approach Control to switch to CTAF. CA was pilot monitoring and made position report on CTAF.Shortly thereafter; received TCAS traffic advisory. Observed; unknown and unreported traffic on TCAS display. Both pilots searched visually for traffic outside. If I remember corrected target disappeared from TCAS display momentarily; then reappeared.While searching visually for traffic; received a TCAS RA and pitch command to reduce descent. Disconnected autopilot and followed command. Continued to search for traffic visually. Received clear of conflict advisory from TCAS. Observed subject traffic now displaying on TCAS behind and above. Continued descending on approach and monitoring TCAS display. Horizontal and vertical separation from traffic continued to increase. Continued on approach and landing profile. Landed without incident.While clearing runway I noticed an aircraft flying approximately parallel to Runway XXL off airport. Contacted traffic on CTAF as I suspected it was the aircraft we received RA for. Aircraft identified itself as helicopter and indicated he had us in sight. I continued to announce on CTAF until we were on ramp. When cancelling IFR with approach control on ground; advised controller we had received an RA for traffic.


Synopsis: Air Carrier flight crew reported an RA while on approach. The Captain reported the Tower at this location was closed earlier than expected and this contributed to the event.