Date: 201908
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Final Approach
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Air Carrier
Reporter function: First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Commercial
Human factors: Communication Breakdown; Situational Awareness
Anomaly: ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: I was completing a QA Observation on this flight; seated on the cockpit jumpseat. While on approach; cleared for the visual approach to Runway XXL at ZZZ; the aircraft was tracking the LOC inbound backing up the visual approach with the ILS XXL; level at 2300 ft; configured to land. Aircraft was between ZZZZZ and ZZZZZ1 on final at GS (Glideslope) Intercept altitude. The TCAS system gave an audible alert 'Traffic...Traffic' The crew immediately looked to see what the alert was and saw the yellow symbology on the MFD (Multi-Function Display) showing a contact off our right wing; slightly behind us... it was a Traffic Advisory only. The symbol then turned white; while showing the other aircraft co-altitude. We continued to watch the TCAS system as the contact continued to edge closer to us; to the point where it was almost on top of our aircraft with the lowest map scale of 5 miles selected; but the symbol was still a white diamond with '+00' displayed... We could not locate the aircraft visually. We never received a Resolution Advisory and had no idea where the other aircraft actually was as we were unable to see the aircraft since it was behind the wing. The Captain called Tower to ask if we had any other aircraft around us. Tower responded that another aircraft had overshot the extended runway centerline for the parallel runway (XXR) and was correcting back. This was unsatisfactory. Tower should have alerted us to this problem; but since we were cleared for the visual approach; they stopped providing separation. However; they should have alerted us to the unsafe situation that was developing when the other aircraft overshot centerline for the other runway. Had this been a PRM (Precision Runway Monitor) approach; we would have received a breakout maneuver from Tower. Tower failed to alert us that another aircraft for the parallel runway had overshot final and was closing with us. They had cleared us for the visual approach and while we are then responsible for separation; we cannot see aircraft behind us that are too close. The TA symbol showed them almost on top of us and they did not say a word until we asked. Tower should maintain closer vigilance with aircraft in their pattern; especially at night with simultaneous parallel approaches. If they see an unsafe situation developing; they need to say something.




Synopsis: Air carrier First Officer reported ATC failure to provide separation of traffic overshooting parallel runway resulted in an NMAC.