ACR WAS INVOLVED IN NMAC WITH MILITARY ACFT WHILE APPROACHING SPS; A JOINT-USE ARPT.

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WE WERE APPROX 10 MI SW OF THE SPS VOR AT 6000 FT. WE WERE GIVEN A CLRNC TO PROCEED DIRECT TO THE VOR; CROSS BELOW 2400 FT AND FLY THE PROC FOR RWY 35. DSNDING THROUGH 4500 FT; THE CTLR CAME ON AND SAID APCH CLRNC WAS CANCELED AND FLY HDG 320 DEGS. IN THE BACKGROUND OF THE XMISSION WAS THE SOUND OF THE RADAR COLLISION WARNING. AT THE SAME TIME THE TCAS ISSUED A TFC ALERT DEPICTING AN ACFT 400 FT BELOW US AND INSIDE THE 2.5 MI RING. I IMMEDIATELY STOPPED THE DSCNT AND BROUGHT THE PLANE BACK TO 4500 FT TO TRY TO MAINTAIN A 500 FT VERT SEPARATION. THE FO SAID HE DIDN'T SEE THE T38 UNTIL IT PASSED US. THE COMBINATION OF THE TCAS INFO AND THE FACT THE COLLISION WARNING WAS GOING OFF DURING THE CTLR'S XMISSIONS. THE AUTOPLT WAS IMMEDIATELY DISCONNECTED AND THE ACFT WAS CLBED BACK TO 4500 FT. FOR SOME REASON EVEN THOUGH THE TCAS SHOULD HAVE ISSUED AN RA; IT DIDN'T. THE CTLR ALSO SAID THE ACFT CAME FROM A 'VFR' PATTERN AT SPS WHICH THEY HAVE NO CTL OF; NOR DO THEY KNOW IF AN ACFT IS GOING TO BE IN CONFLICT WITH ARRIVING PAX ACFT UNTIL IT'S TOO LATE. THIS WAS THE SECOND SIMILAR EVENT OF THAT DAY. OBVIOUSLY THERE'S SOMETHING WRONG. 1) DISCONTINUE MIL OPS DURING ARR OF FAR PART 121 ACFT. 2) PROPER CTLR TRAINING OR ACCOUNTABILITY OF THE MIL TO A SAFETY PROGRAM. I HAVE ENCOUNTERED NUMEROUS OPERRORS THERE I HAVE REPORTED TO THE COMMANDING OFFICER OF THE RADAR INSTALLATION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT HE HAS MADE NUMEROUS FLTS INTO SPS; ALSO A MIL TRAINING BASE. WHEN ARRIVALS ARE LNDG TO THE NORTH; T-38'S CONDUCT LEFT OVERHEAD TFC PATTERNS FOR RWY 33L AND T-37'S USE 33R WITH RIGHT TFC. COMMERCIAL CARRIERS ARE ASSIGNED RWY 35 AND TYPICALLY ARRIVE FROM THE WEST OVER THE SPS VOR. WHILE DESCENDING FOR AN APCH; CIVILIAN ACFT MUST DESCEND THROUGH THE T-38 TFC PATTERN ALT OF 4000 FT. THIS CREATES AN OBVIOUS CONFLICT. THE REPORTER BELIEVES THAT ATC SHOULD MAKE AN EFFORT TO SEPARATE TFC WHEN COMMERCIAL CARRIERS ARE INBOUND.