WAKE ENCOUNTER.

Narrative

OUR FLT WAS BEING VECTORED TO THE ILS RWY 4R BEHIND A B757. WHILE DSNDING THROUGH 5600 FT MSL WE ENCOUNTERED THE WAKE TURB. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND ARRESTED THE ROLLING MOMENT. THIS ENCOUNTER WAS BRIEF AND MILD COMPARED TO SOME IN THE PAST. STILL A PROB THAT NEEDS TO BE ADDRESSED. THE ISSUING OF WAKE TURB ADVISORIES DOESN'T SOLVE THE SAFETY PROB. WE RECEIVED SEVERAL ADVISORIES FROM APCH AND TWR; WHICH TIED UP VALUABLE RADIO TIME; BUT DIDN'T HELP US AVOID THE WAKE. AS IT WAS; WE ONLY SAW THE B-757 BRIEFLY WHILE BEING VECTORED FOR THE APCH. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAYS THAT THE FLC ANTICIPATED THE MAJOR ROLLING MOMENT BECAUSE THEY FELT A FEW NIBBLES BEFORE IT HIT. SO THEY DISCONNECTED THE AUTOPLT JUST AS THEY STARTED TO ROLL AND WERE ABLE TO KEEP IT TO ABOUT 10 DEGS L BANK AND A 10 DEG L HDG CHANGE. THIS IS THE RPTR'S SECOND WAKE TURB RPT AND THOUGH THIS WAS MILDER HE IS JUST AS STRONGLY CONVINCED THAT THE ADVISORIES ARE OF LIMITED VALUE. SPACING IN- TRAIL AND ALT SEPARATION; WITH THE HVYS BEING LOWER IS SOMETHING WE SHOULD BE DOING ACCORDING TO THE RPTR.