AN ACR DC9 FLC COMPLAINS THAT TFC WATCH ACFT ARE OFTEN IN THE VICINITY OF THE ILS COURSE FOR RWYS 17 AND 19 AT SDF. IN THIS CASE; AN ACFT PASSED 300 FT BELOW THEIR ACFT AND THE APCH CTLR DID NOT FOREWARN THE FLC. THE RPTR SAID THAT THIS TYPE OF ACTIVITY ALSO OCCURS AT BNA.

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IN SDF THEIR NEWS TFC ACFT STAY RIGHT BY THE ILS COURSE FOR RWYS 17 AND 19. ON THIS FLT WE GOT A TA ON TCASII. IT LOOKED LIKE THE TARGET ON TCASII WAS RIGHT BELOW US. IT SHOWED ACFT 300 FT BELOW US. WE STAYED HIGH ON THE GS. APCH TOLD US AFTER WE QUESTIONED; THE ACFT HAD A VISUAL ON TFC ON THE FINAL AND THEY STAYED CLR OF FINAL. DO WE HAVE TO HAVE THESE ACFT SO CLOSE? I NEVER SAW THE ACFT AND WAS NEVER WARNED OF TFC. WE NEED TO DO SOMETHING ABOUT THIS. I ALSO HAD SIMILAR PROB ONCE IN BNA. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR IS A DC9-30 CAPT AND HE HAS HAD TWO CLOSE ENCOUNTERS WITH TFC WATCH ACFT AT SDF WHILE APCHING FROM THE N. IN THIS CASE; HE WAS HIGH ON THE GS WHEN HE GOT A TA ON HIS TCASII AND NOTED THAT AN ACFT; LATER DETERMINED TO BE A HELI; WAS 300 FT BELOW HIM AT 12 O'CLOCK POS. HE COMPLAINED TO THE APCH CTLR; BUT THE CTLR SIMPLY TOLD HIM THAT IT WAS A TFC WATCH ACFT THAT HAD HIM IN SIGHT. AFTER LNDG; THE RPTR SAID THAT HE SPOKE TO THE TWR SUPVR WHO SAID THAT IT WAS A HELI AND THAT THE OP IS LEGAL AND THAT THE HELI WAS SLIGHTLY OFF THE CTRLINE OF THE RWY AND MAINTAINING VISUAL SEPARATION FROM APCH TFC. THE CAPT SAID THAT HE NORMALLY CHANGES HIS TCASII TO 'TA ONLY' MODE FOR APCHS TO CANCEL NUISANCE RA'S FROM PARALLEL ACFT. HE SAID THAT HIS PRACTICE PREVENTED AN RA IN THIS EVENT. HE ATTEMPTED TO EXPLAIN THE PROB OF UNEXPECTED TFC TO THE APCH CTLR AND THE TWR SUPVR; BUT HE SAID THAT HE ENDED UP FRUSTRATING EVERYONE WITH HIS EFFORT. HE HAS ALSO RPTED THESE EVENTS TO A PLT GROUP AND HIS COMPANY SAFETY PERSONNEL.