POTENTIAL CONFLICT AFTER RADAR VECTORING PLACES ACFT X IN PROX OF MULTIPLE ACFT.

Narrative

ON DOWNWIND FOR LNDG RWY 11R ILS MSP; HDG 310 DEGS; APCH REQUESTED A TURN TO 070 DEGS FOR BASE LEG. AT ABOUT 030 DEGS; TCASII SHOWED TFC CONFLICT AND WE SAW A 757 AT 12 O'CLOCK. APCH IMMEDIATELY SAID TURN L 360 DEGS VECTORING US BEHIND THE 757. WE TOLD APCH WE HAD 757 IN SIGHT. WE WERE NOW PASSING THROUGH RWY 11R ILS LOC AND WERE WORRIED ABOUT TFC ON ILS RWY 11L. SECONDS LATER WE SPOTTED A 727 TURNING FINAL FOR RWY 11L APPROX 1000 FT ABOVE US. CTLR REQUESTED AN IMMEDIATE TURN TO 140 DEGS. TCASII WAS SHOWING CONFLICT WITH 727. WE PASSED THROUGH ILS RWY 11R AGAIN AND CTLR ASKED IF WE WERE INTERCEPTING ILS TO RWY 11R. WE STATED WE HAD NOT BEEN CLRED FOR THE APCH. CTLR THEN CLRED US FOR APCH TO RWY 11R. NEW VOICE ON RADIO. CTLR CHANGE. TOTALLY FORGOT TO SWITCH US TO MSP TWR FOR LNDG CLRNC. HAD WE NOT BEEN ABLE TO SEE THE CONFLICTING TFC DURING THE APCH; THIS SIT COULD HAVE BECOME VERY CONFUSING AND UNSAFE. AS IT WAS; THE APCH VECTORING AND PERFORMANCE OF THE ENTIRE APCH BY APCH CTL WAS MARGINAL.