Date: 202107
Local time of day: 1801-2400
Location: S56.TRACON, UT
Weather elements / visibility: Turbulence; Thunderstorm
Aircraft: Medium Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B SLC
ATC / advisory: TRACON S56
Second aircraft: Small Transport; Low Wing; 2 Turbojet Eng
Reporter organization: Government
Reporter function: Approach; Supervisor / CIC
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Workload; Communication Breakdown; Confusion; Situational Awareness; Time Pressure
Anomaly: ATC Issue All Types; Deviation - Altitude Overshoot; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Weather; Airspace Structure; Human Factors; Procedure
Primary problem: Procedure

Narrative: Working 4 sectors combined; and Controller in Charge. SLC was in a South Operation; Visual Airspace; Visual Approaches. Weather was VMC but visibility was diminishing and was marginal. There are thunderstorms throughout the sectors in my airspace. Lightning reported on the finals to all Runways; airspeed fluctuations reported on final; audible Wind Shear Alerts continuous all runways; 15 knot wind shift approaching the SLC Airport. Light to occasional moderate chop reported in the area. Tailwinds on final.Aircraft Y vectored to a 15 mile right base; cleared for Visual Approach to Runway 17 at SLC; switched to Tower. Aircraft X at 210 knots given descent to 8;000 feet abeam the SLC Airport; expecting Runway 16R; on the RNAV arrival being sequenced with other traffic within my sector(s) and on final. Traffic Management Unit calls down to TRACON through speaker in the Supervisor's console that Aircraft Y had a Lightning Strike and coordinated a heading 270 at 9;000 feet. I responded Radar Contact. Tower initiated the Heading 270 on a 9 mile final at 9;000 feet; which you never do; however; Aircraft Y was coordinated at 9;000 feet.  I kept Aircraft X expediting to 6;000 feet; which would not be an issue as long as Aircraft Y leveled at 9;000 feet. This was not the case as I observed Aircraft Y continuing descent through 8900 feet and continuing.  Recognizing this immediately; Aircraft Y appeared to be an Emergency aircraft not knowing what altitude he would be stopping at; I issued traffic to Aircraft X followed by a Traffic Alert with a heading 270 immediately to avoid a mid-air collision; all the while I was still not talking to Aircraft Y performing evasive maneuvers in my airspace.As soon as Aircraft X was past Aircraft Y I would then have divergence. I turned Aircraft X to heading 340; and issued a Low Altitude Alert and climbed him immediately to 7800 feet; while doing so I see Aircraft Y turning to the same north heading 340 at 8000 feet; with Aircraft X just West of Aircraft Y on a parallel course; and not talking to Aircraft Y in my airspace; not having lateral separation; I immediately turned Aircraft X to heading 310; all the while trying my best to achieve some sort of radar separation; and avoid a collision; until I find out who is talking to Aircraft Y. Aircraft Y at 8;000 feet is not what coordinated nor approved by me in my airspace; and a Heading 270 off the finals is never performed; for this exact reason. This is an unsafe operation with traffic in the downwind. Aircraft Y at 8;000 feet leaves no options at all.After determining the adjacent sector controller; who is only certified on those positions; was working Aircraft Y; in which Tower switched him to my airspace; when I had conflicting traffic. The adjacent sector controller provided zero communications to me; even though I repeatedly asked who was working Aircraft Y and what is he doing?  After I had Aircraft X squared away; they just happened to say 'Aircraft Y had your Aircraft X in sight and was maintaining visual separation.'This would have been nice to know.When an aircraft is coordinated to be 9;000 feet then have the aircraft be at 9;000 feet; not at 8;000 feet; which leaves the final sector Controller absolutely no way out. No attempt was made to by Tower who assigned 8;000 feet; or by the adjacent sector who received the aircraft at 8;000 feet to advise the sector who owns the airspace with an aircraft in direct conflict. When a heading of 270 and 9;000 feet is coordinated with another sector; a Departure Only Sector; then make sure he enters the airspace for which that specific coordination was originally made; and not another sector that has conflicting traffic with that type of coordination.No coordination or even a point out was attempted to be made to the appropriate sector in which the vital coordination directly impacts. When Visual Separation is applied between two aircraft that are in direct conflict with each other; it is absolutely a top priority to ensure that all parties involved receive this valuable bit of information.When a Controller takes it upon themselves to accept the responsibility of an aircraft in someone else's airspace at an altitude that is in direct conflict with an aircraft that you are not in communication with and at a different altitude than what was previously coordinated; then it might be a top priority to advise Controller working the aircraft in his own airspace that he is in direct communications with that visual separation is being applied. When a controller is taking evasive actions to prevent a mid-air collision with an aircraft that you are talking to; that is not in your airspace; and you are providing control instructions to; don't sit quietly when you hear 'Who is talking to Aircraft Y'?




Synopsis: A TRACON Controller reported an aircraft was issued incorrect go-around instructions which placed it into conflict with another aircraft and below the Minimum Vectoring Altitude. Unbeknownst to the reporter the go-around aircraft which was on another controller's frequency was maintaining Visual Separation.