B737-800
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Situational Awareness; Workload; Distraction
Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Unstabilized Approach
Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Human Factors; Airspace Structure
We were descending cleared direct OXABY maintain 3;700 ft. Approaching approximately 4;000 ft. ATC issued a Traffic Warning 'pop up traffic 5 miles 4;000 ft. converging; moments later I had visual on the traffic and requested a hard right turn to avoid. We turned approximately 90 degrees right. When clear of traffic we were vectored left turn back to the airport. The First Officer (Pilot Flying) who was familiar with the airport said he had the airport I called the field insight and we began approach to Runway 4. Initially we were on glideslope and PAPI but no Localizer. I verified that ILS frequencies were correct. Then glideslope started showing us low still on PAPI. I concluded something was amiss and called for a go around with ATC. ATC said they suspected we were lined up on Runway 5 at GHY approximately 10 miles to the west with no previous warning. We were given vectors back to a 19 miles downwind cleared to OXBY and cleared ILS Runway 4 at GSP. Approach and landing was normal and standard. I canceled IFR clearance on the ground (Tower was closed) and continued to the gate.There were several circumstances that contributed to this event; first and foremost was the traffic alert at low altitude that required evasive action. After being turned back to the airport a bit task saturated led to some navigational and situational awareness being a bit behind. This is why I elected to initiate a go around. This gave us the crew time to set up the approach with no traffic distractions and conduct a normal standard approach and landing to the airport. In addition this was the First Officer flying first line trip after completing IOE with 29 hours in the B737. As pilot monitoring; I needed to be more attentive than flying with a pilot with more experience. Had the Tower been open and operating may have also helped in this situation.
B737 Captain reported distraction and workload due to a traffic conflict that caused them to line up with the wrong runway.