PLT IN C560 INBOUND TO PIT EXPERIENCED SEVERE WAKE TURB WHEN THE FLT WAS TURNED IN APPROX 4 MI BEHIND A B737 AND CLRED FOR AN ILS APCH. THE RPTR CLAIMS THE PLT STATED AFTER HE HAD LANDED THAT THE ACFT HAD MADE A COMPLETE ROLL AT 4000 FT.

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AT APPROX XA35 I CLRED ACFT #2 FOR AN ILS APCH TO RWY 32 AT PIT. I ADVISED HE WAS 4 MI BEHIND A B737 AND BELIEVE I CAUTIONED HIM ABOUT THE WAKE TURB. VERY SOON THEREAFTER (LESS THAN 1 MIN); ACFT #2 SAID HE HAD EXPERIENCED SEVERE TURB AND WAS MOVING OFF THE RWY 32 FINAL. I PROCEEDED TO QUESTION HIM ABOUT HIS TFC AND THE ARPT TO WHICH HE REPLIED HE HAD THE ARPT IN SIGHT. I CLRED HIM FOR A VISUAL APCH AND SWITCHED HIM TO THE TWR. ACFT #2 MENTIONED BEING INVERTED ON THE FREQ AND LATER IN A PHONE CONVERSATION CONFIRMED HE HAD BEEN ROLLED INVERTED BY WHAT HE BELIEVED WAS WAKE TURB. SEPARATION WAS AT 4+ MI WHEN THE INCIDENT OCCURRED AND CONTINUED TO INCREASE AS ACFT #2 SLOWED EVEN FURTHER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED AT THE TIME OF THE INCIDENT; CONDITIONS WERE FROM MVFR TO IFR AND THAT THE TFC SIT WAS BECOMING VERY BUSY. THE B737 ACFT HAD STARTED FINAL APPROX 30 MI FROM THE ARPT AND HAD BEEN CLRED FOR A STRAIGHT-IN APCH. THE C560 CAME IN FROM THE W AND PUT ON A VECTOR TO FOLLOW THE B737. VERY SHORTLY AFTER THE C560 TURNED ONTO THE FINAL; THE PLT ADVISED HE HAD ENCOUNTERED SEVERE WAKE TURB; RECOVERED AFTER BECOMING INVERTED; AND MOVED OFF THE R SIDE OF THE LOC. HE THEN SIGHTED THE ARPT AND WAS CLRED FOR A VISUAL APCH. AFTER LNDG; THE PLT CONTACTED THE APCH FACILITY AND ALLEGEDLY STATED THAT HE HAD BEEN COMPLETELY ROLLED BY THE WAKE ENCOUNTER. NO INJURIES OR DAMAGE TO THE ACFT WERE RPTED.