A BAE-3201 ENCOUNTERS WAKE TURB 4 MI BEHIND A B737 ON APCH TO STL.

Narrative

WHILE ON THE VISUAL APCH TO RWY 30R AT STL; USING THE ILS AS BACKUP NAV; WE ENCOUNTERED WAKE TURB FROM A B737 ABOUT 4 MI AHEAD OF US ON THE VISUAL TO THE SAME RWY. THE ACR FLT NUMBER WAS XX. THEY WERE WAY ABOVE THE GS/PATH FOR THAT RWY. WE HAD BEEN TOLD FROM APCH ABOUT ACR POS; AND WE WERE MAINTAINING VISUAL SEPARATION FROM THEM. I HAD ALTERED MY COURSE TO THE R OF CTR TO AVOID THEIR WAKE; AND I REMAINED 2 DOTS HIGH ON THE GS SINCE WE WERE ABLE TO SEE HIS ALT -- HOW HIGH THEY WERE; ON OUR TCASII; BUT WE STILL GOT ROCKED AROUND A BIT. THE WAKE TURB AND THE UPSET WE EXPERIENCED WAS NOT TOO BAD; IT WAS ONLY ABOUT 15 DEGS BANK AND 2 DEGS PITCH DOWN; BUT BEING THAT HIGH ON THE GLIDE PATH AND APPROX 4 MI IN TRAIL SHOULD; UNDER MOST CIRCUMSTANCES; KEEP US WELL ABOVE THE WAKE OF ANY ACFT AHEAD OF US. BUT; I HAVE NOTICED THAT ACR MAKES A STANDARD PRACTICE OF REMAINING WELL ABOVE GS/PATH CAUSING MORE THAN NORMAL AMOUNTS OF ENCOUNTERS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN THE WAKE TURB CALLBACK STUDY. RPTR WAS INFORMED OF A B737; DSNDING FROM A HIGHER ALT; BEING IN FRONT OF HIS ACFT. THIS IS A CONSTANT SOURCE OF FRUSTRATION FOR THIS TURBOPROP PLT AS IT MEANS THAT HE HAS TO GO THROUGH THE PRECEDING ACFT WAKE SOMETIME DURING THE APCH. HE WAS TRYING TO FLY HIGHER THAN USUAL JUST SO HE COULD AVOID WAKE TURB ON FINAL; BUT COULD NOT FLY AS HIGH AS THE STEEPLY DSNDING B737 IN FRONT OF HIM. THEREFORE; HE HAD A WAKE ENCOUNTER.