Narrative:

Arrived in the slc area via the spane arrival, and were on vectors to the localizer runway 34R approach. GS was reported OTS. Approach gave us a vector to intercept the localizer and descend from 15000 ft to 8000 ft. Descending through 14000 ft, approach asked us to increase our descent rate and said we had VFR traffic ahead at 12000 ft. We increased the descent rate (first officer was flying and extended the speed brakes). I observed traffic on the TCASII display at about the area approach had called it. That traffic seemed to be drifting toward the localizer course. Approach asked if we had the traffic visually. I said we were IMC, and approach told us to turn immediately right about 60 degrees. The TCASII display had turned yellow and the traffic alert sounded. It looked to me like we were not going to be able to miss the traffic by turning, so I told the first officer to climb the aircraft, and the TCASII display changed from yellow to red and issued the 'climb' alert. First officer added power climbing about 1500 FPM. We broke out of the clouds and I saw the traffic moving from right to left, it appeared to be a C210. I could make out the pilot in the aircraft. I estimate we came within 100 ft vertically and 500 ft or less horizontally. After recovery from the escape maneuver, we continued uneventfully to landing. I asked approach control if they 'were talking with that aircraft we just almost hit.' they said they were not, that he had been 'loitering' around that area for some time. Supplemental information from acn 561603: a TA suddenly appeared at our 2 O'clock position, 2 mi, converging, about 500 ft below and climbing. Within 15 seconds, the traffic generated a TCASII RA. At about the same time, approach control issued a right turn from our heading of approximately 350 degrees to 020 degrees. I followed the TCASII commands to climb while turning to 020 degrees (autoflt modes had been disconnected at this point). TCASII commanded an increase in climb rate, to which I complied until TCASII alerted 'clear of traffic.' we broke out of the WX at about the time we cleared the traffic. My first reaction was to question why the controller wasn't aware of and didn't notify us of the traffic earlier, and why he gave us a descent so close to climbing traffic. Perhaps it 'popped up' as a surprise to him also. Secondly, a turn away from the direction of the approaching traffic, and/or a level off for us seemed more appropriate.

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Original NASA ASRS Text

Title: B737-800 CREW HAD AN NMAC WITH A C210 IN S56 CLASS E AIRSPACE.

Narrative: ARRIVED IN THE SLC AREA VIA THE SPANE ARR, AND WERE ON VECTORS TO THE LOC RWY 34R APCH. GS WAS RPTED OTS. APCH GAVE US A VECTOR TO INTERCEPT THE LOC AND DSND FROM 15000 FT TO 8000 FT. DSNDING THROUGH 14000 FT, APCH ASKED US TO INCREASE OUR DSCNT RATE AND SAID WE HAD VFR TFC AHEAD AT 12000 FT. WE INCREASED THE DSCNT RATE (FO WAS FLYING AND EXTENDED THE SPD BRAKES). I OBSERVED TFC ON THE TCASII DISPLAY AT ABOUT THE AREA APCH HAD CALLED IT. THAT TFC SEEMED TO BE DRIFTING TOWARD THE LOC COURSE. APCH ASKED IF WE HAD THE TFC VISUALLY. I SAID WE WERE IMC, AND APCH TOLD US TO TURN IMMEDIATELY R ABOUT 60 DEGS. THE TCASII DISPLAY HAD TURNED YELLOW AND THE TFC ALERT SOUNDED. IT LOOKED TO ME LIKE WE WERE NOT GOING TO BE ABLE TO MISS THE TFC BY TURNING, SO I TOLD THE FO TO CLB THE ACFT, AND THE TCASII DISPLAY CHANGED FROM YELLOW TO RED AND ISSUED THE 'CLB' ALERT. FO ADDED PWR CLBING ABOUT 1500 FPM. WE BROKE OUT OF THE CLOUDS AND I SAW THE TFC MOVING FROM R TO L, IT APPEARED TO BE A C210. I COULD MAKE OUT THE PLT IN THE ACFT. I ESTIMATE WE CAME WITHIN 100 FT VERTLY AND 500 FT OR LESS HORIZLY. AFTER RECOVERY FROM THE ESCAPE MANEUVER, WE CONTINUED UNEVENTFULLY TO LNDG. I ASKED APCH CTL IF THEY 'WERE TALKING WITH THAT ACFT WE JUST ALMOST HIT.' THEY SAID THEY WERE NOT, THAT HE HAD BEEN 'LOITERING' AROUND THAT AREA FOR SOME TIME. SUPPLEMENTAL INFO FROM ACN 561603: A TA SUDDENLY APPEARED AT OUR 2 O'CLOCK POS, 2 MI, CONVERGING, ABOUT 500 FT BELOW AND CLBING. WITHIN 15 SECONDS, THE TFC GENERATED A TCASII RA. AT ABOUT THE SAME TIME, APCH CTL ISSUED A R TURN FROM OUR HDG OF APPROX 350 DEGS TO 020 DEGS. I FOLLOWED THE TCASII COMMANDS TO CLB WHILE TURNING TO 020 DEGS (AUTOFLT MODES HAD BEEN DISCONNECTED AT THIS POINT). TCASII COMMANDED AN INCREASE IN CLB RATE, TO WHICH I COMPLIED UNTIL TCASII ALERTED 'CLR OF TFC.' WE BROKE OUT OF THE WX AT ABOUT THE TIME WE CLRED THE TFC. MY FIRST REACTION WAS TO QUESTION WHY THE CTLR WASN'T AWARE OF AND DIDN'T NOTIFY US OF THE TFC EARLIER, AND WHY HE GAVE US A DSCNT SO CLOSE TO CLBING TFC. PERHAPS IT 'POPPED UP' AS A SURPRISE TO HIM ALSO. SECONDLY, A TURN AWAY FROM THE DIRECTION OF THE APCHING TFC, AND/OR A LEVEL OFF FOR US SEEMED MORE APPROPRIATE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.