AN ACR WDB CAUSED SOME CONFUSION WHEN ITS APCH CLRNC WAS CHANGED AT THE LAST MIN. THERE WAS A TCASII CLB COMMAND.

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DENVER TO SEATTLE VIA THE CHINS 2 ARR; FOLLOWED BY AN ILS TO RWY 16R; AND VISUALS TO RWY 16; ACCORDING TO THE SEATTLE ATIS INFO. AT AUBURN INTXN WE TURNED TO 340 DEG HDG AND CONTACTED SEATTLE APCH. THEY CLRED US DOWN AND VECTORED US TOWARD RWY 16R. WHEN WE HAD TURNED TO A 260 DEG HDG; APCH CTL ASKED US IF WE HAD THE ARPT IN SIGHT. MY MISTAKE WAS TO ADMIT THAT WE HAD THE ARPT. WE WERE SUDDENLY CLRED FOR A HUSKY VISUAL APCH TO RWY 16L. THE ONLY APCH THAT I COULD FIND WAS A HUSKY VISUAL TO RWY 16R. THEY ALSO REQUESTED THAT WE MAINTAIN 5000 FT UNTIL ABEAM HUSKY STADIUM. SINCE I WAS NOT FAMILIAR WITH DOWNTOWN SEATTLE; I HAD DIFFICULTY LOCATING HUSKY STADIUM; AND WE STRAYED TO THE R OF OUR COURSE. THE PLT OF THE ACFT THAT HAD BEEN CLRED FOR A VISUAL TO RWY 16R CALLED TO FIND OUT WHERE OUR WDB WAS GOING. SEATTLE SWITCHED US TO RWY 16R AND THE OTHER ACFT TO RWY 16L. TO ADD TO THE CONFUSION; WE THEN GOT A TCASII TA; FOLLOWED BY A CLB COMMAND. WE DECIDED TO CONTINUE THE APCH AND LANDED ON RWY 16R. PARALLEL VISUAL APCHS TO RWYS 16L&R AT SEATTLE SHOULD BE DISCONTINUED BEFORE SOMEONE GETS KILLED. YOU CAN BE SURE THAT I WILL NEVER ACCEPT SUCH AN APCH. SUPPLEMENTAL INFO FROM ACN 250092: THE CTLR SUBSEQUENTLY CLRED US FOR A VISUAL RWY 16R AND GAVE THE LTT RWY 16L AT WHICH POINT OUR TCASII GAVE US AN RA TO CLB WHICH SIMPLY MADE A BAD SIT WORSE. THE CAPT HAD NO IDEA WHAT THE VISUAL APCH REQUIRED HIM TO DO AT THAT POINT; WHERE HE NEEDED TO TURN INBOUND AND I DIDN'T COMMUNICATE IF EFFECTIVELY. THE LTT CAPT DID A GOOD JOB OF KEEPING US IN SIGHT AND NOT TURNING IN FOR THE APCH. HE MAINTAINED SEPARATION WHICH PREVENTED THIS FROM BEING A VERY SERIOUS INCIDENT. IF THE CTLR HAD SIMPLY SAID CLRED THE VISUAL RWY 16L WE MIGHT NOT HAVE HAD THE PROB BUT BECAUSE WE WERE LOOKING/SWITCHING PLATES AND CONCERNED ABOUT COMPLYING WITH A SPECIFIC CHARTED PROC; WE COLLECTIVELY TURNED A SIMPLE APCH INTO A HAZARDOUS SIT. SUPPLEMENTAL INFO FROM ACN 248757: IT IS ALSO DIFFICULT TO BACK FLYING CREW MEMBERS UP WHILE THEY ARE FLYING VISUAL PROCS. WE ARE NOT SUPPLIED THE APCH PLATES TO DO SO.