AN SF340B ENCOUNTERS WAKE TURB FOLLOWING A B757 ACFT ON APCH INTO MIA.

Narrative

CLRED FOR APCH FOR RWY 9R AT MIA; TOLD TO MAINTAIN 190 KTS UNTIL WITHIN OM. AT 20 MI OUT FROM DPH VOR/DME; WHILE ON LOC FOR RWY 9R; ATC ADVISED A B757 WOULD BE CLRED 4 MI AHEAD AND TO MAINTAIN SPD. B757 INTERCEPTED LOC AT 13 MI OUT; AT 4000 FT PLACING US 4 MI BEHIND AND 1000 FT BELOW. WE BRIEFED FOR EVASIVE ACTION IN EVENT OF WAKE AND MAINTAINED 190 KTS. THIS PROC IS STANDARD OP FOR MIA AND IS A CONSTANT SOURCE OF FRUSTRATION FOR ALL TURBOPROP ACFT; IE; WAKE SINKS NORMALLY BTWN 800-1000 FPM. AT 190 KTS YOU TRAVERSE 3.16 MI PER MIN. IT WAS NOT A QUESTION OF 'IF' YOU WILL INTERCEPT WAKE; IT IS A QUESTION OF WHEN. WE ENCOUNTERED A ROLLING MOTION SHEAR WHICH ROTATED OUR HEAVILY LOADED CRAFT 35 DEGS L; THEN R 15 DEGS; REQUIRING FULL SCALE AILERON DEFLECTION TO RECOVER. MIA APCH HAS BEEN ASKED OVER AND OVER AGAIN TO BRING INTERCEPTING ACFT IN AT THE SAME ALT RATHER THAN 1000 FT HIGHER. WE HAVE HAD 2 FLT ATTENDANTS THROWN AROUND IN THE PAST 3 MONTHS BECAUSE OF THIS. THIS HAS BEEN DONE FOR OVER 2 YRS AND HAS CAUSED PROBS SINCE ITS IMPLEMENTATION. WE HAVE MADE IT A POINT TO BRIEF THIS PROB AS SOON AS WE REALIZE THE PROC IS BEING USED WHILE WE ARE TRAILING ON THE APCH. UNLESS ALL ACFT ARE AT THE SAME ALT OR THE HEAVIES KEPT 1000 FT BELOW; THIS PROB WILL CONTINUE UNTIL SOMEONE IS SEVERELY HURT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR TOOK PART IN WAKE TURB STRUCTURED CALLBACK PROGRAM. RPTR SUBMITTED RPT MAINLY TO COMPLAIN ABOUT THE REPEATED TFC PATTERN USED TO KEEP TURBOPROPS LOWER THAN TURBOJETS UNTIL GS INTERCEPT. THIS PROC ALWAYS RESULTS IN THE LOWER ACFT FLYING THROUGH ANY WAKE OF A HEAVIER ACFT. THIS INCIDENT WAS INCONVENIENT AND UNCOMFORTABLE; BUT THE LOSS OF CTL DID NOT LAST TOO LONG AND IT WAS NOT CLOSE TO THE GND. RPTR HAD SEVERAL PAX COMPLAINTS REGARDING THE TURB BUT NO INJURIES. LOSS OF CTL LASTED ABOUT 10 SECONDS.