FLC OF LTT HAD CONFLICT WITH SMA ON APCH TO TYS.

Narrative

FLT FROM NASHVILLE TO KNOXVILLE; TN; HAD A NEAR MISS SITUATION WITH A LIGHT TWIN IN THE APCH PHASE OF THE FLT. SHORTLY AFTER WE CONTACTED TYS APCH; WE HEARD APCH NOTIFY A LIGHT TWIN (ON AN APPROX L BASE TO 23R) OF OUR POS AND THAT HE WAS CLRED FOR A VISUAL APCH TO 23R. WE WERE CONSIDERABLY FARTHER BEHIND THAT ACFT AND MANEUVERING FOR A R BASE TYPE TURN. OUR ALT WAS APPROX 4000 WHEN WE BEGAN OUR TURN TO THE RWY. OUR SPD WAS APPROX 170 KTS. WE WERE ADVISED THAT AS WE TURNED R TOWARD THE RWY THE TWIN WOULD BE AT OUR 12 O'CLOCK POS. I SAW THE ACFT AND RPTED THAT TO APCH. THEY CLRED US FOR A VISUAL TO 23R AND TO MAINTAIN CONTACT WITH THE TWIN. AS WE ROLLED OUT ON THE FINAL APCH COURSE I LOST VISUAL CONTACT WITH THE TWIN. THE CAPT NEVER SAID WHETHER OR NOT HE EVER SAW THE OTHER ACFT. THE NEXT TIME APCH CALLED; HE CHANGED OUR SEQUENCE. HE SAID WE WOULD LAND FIRST AND THEN THE TWIN. AT THIS POINT I WAS CONFUSED AS TO HOW THE OTHER ACFT WAS GOING TO BE BEHIND US. SUDDENLY; THE CAPT NOTICED THE OTHER ACFT DIRECTLY BELOW US. I ESTIMATE THAT WE OVER-TOOK THE TWIN AND PASSED OVER HIM BY APPROX 2-500 FT AND 500-1000 FT HORIZLY. WE MAINTAINED OUR ALT AND HE PROCEEDED TO TURN R AND BROKE OFF HIS APCH. THERE WAS A DEFINITE BREAKDOWN OF COM. I DIDN'T TELL THE CAPT WHEN I LOST SIGHT OF OUR TFC. THE CTLR NEVER ADVISED US OF OUR CLOSE PROX; EVEN THOUGH WE WERE CLRED FOR A VISUAL APCH. IT SURE GOT OUR ATTN. THANK GOD WE SAW HIM IN TIME.