B737 Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Workload
Conflict NMAC; Inflight Event / Encounter Unstabilized Approach
Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Executed Go Around / Missed Approach
Procedure; Aircraft; Human Factors
We were cleared for a visual approach after [transitioning from an instrument approach]. We were told to follow a Caravan and were number two for the airport. I heard the Tower talk to a Cherokee and instructed them to enter the downwind and follow a 737 on final (us). As we got closer to the runway I queried the Tower about our traffic. They said we were now number one for the runway and company 737 was departing ahead of us. As we were lining up with the runway at about 500 ft. AGL I saw a Cherokee on a close in base leg to our left. He was joining final in front of us. I called out the traffic to the First Officer who was flying. He saw the traffic and pitched down to avoid the aircraft. The Cherokee passed directly above us by about 100-200 ft. Our approach was now unstable so I called for a go around. The First Officer asked if we were clear of the traffic (we now were) and then initiated the go around at 200 ft. AGL. We maneuvered to rejoin a visual approach to a landing. I reported a near miss to the Tower. I later found out the Cherokee did not have a transponder which explains why there was no TCAS alert. This also effected the ability of the Tower to track them. If I had known the Cherokee didn't have a transponder I would have been more vigilant about making sure we acquired visual contact.
B737 Captain reported NMAC with a Cherokee on final approach; resulting in a go-around.