ACR CREW LEAVES ASSIGNED ALT BEFORE BEING ESTABLISHED ON ILS LOC AS CLRED AT SLC; UT.

Narrative

WE WERE DOING AN APCH INTO SLC AFTER AN ALL NIGHT FLT FROM ANC. WE WERE TALKING TO APCH CTL ON VECTORS FOR AN ILS TO RWY 16L. WE WERE INITIALLY IN AND OUT OF THE CLOUDS. WE WERE GIVEN A CLRNC OF 'MAINTAIN 10000 FT ON A 190 DEG HDG UNTIL INTERCEPTING THE LOC; CLRED FOR THE ILS RWY 16L APCH. APCH CTL THEN TOLD US TO GO TO TWR FREQ. WE THEN BROKE OUT OF THE CLOUDS AND SAW THAT IF WE MAINTAINED 10000 FT UNTIL WE WERE EXACTLY ON THE LOC WE WOULD BE VERY HIGH FOR THE APCH. WE STARTED DOWN TO THE RWY. WE WERE GETTING LINED UP WITH THE RWY (BUT NOT ON THE LOC YET). WE TRIED TO TELL THE ATC CTLR WE SAW THE RWY FOR A VISUAL APCH; BUT DUE TO RADIO CONGESTION WE COULD NOT GET A WORD IN. WHEN THE RADIO CONGESTION STOPPED; THE APCH CTLR CAME ON THE TWR FREQ AND TOLD US TO CLB BACK TO 10000 FT AND TURN TO A HEADING. WE TOLD THE CTLR WE HAD THE RWY IN SIGHT AND THE CTLR CLRED US FOR A VISUAL APCH. TECHNICALLY WE SHOULD HAVE MAINTAINED 10000 FT UNTIL WE WERE ON THE LOC SINCE WE WERE ONLY CLRED AN ILS APCH AND NOT A VISUAL INITIALLY. THE CAPT WAS FLYING AND I WAS WORKING THE RADIO. I MENTIONED THAT WE WERE SUPPOSED TO STAY AT 10000 FT UNTIL WE WERE ON THE LOC; BUT HE SAID IT WOULD BE OK. I PROBABLY SHOULD HAVE BEEN MORE FORCEFUL IN TELLING HIM TO MAINTAIN ALT UNTIL WE WERE ON THE LOC. FAMILIARITY WITH THE ARPT AND FATIGUE AFTER AN ALL NIGHT FLT CONTRIBUTED TO THE SIT. THE ATC CTLR ALSO SHOULD NOT HAVE GIVEN US SUCH A HIGH TURN ON TO FINAL.