AUS TRACON CTLR DESCRIBED CONFLICT EVENT AT 6000 WHEN ONE ACFT ON BASE CHANGED TO TWR; TWR CLRED ACFT FOR VISUAL; CONFLICTING WITH OTHER ACFT.

Narrative

WITH TRAINING COMMENCING ON RADAR W; I WAS WORKING RADAR E; WE WERE SHARING THE FINAL APCH TO AUSTIN. RADAR W WAS WORKING ACFT X; AN ARR FROM THE NW AND WAS TO BE #1 ARR; I WAS WORKING ACFT Y FROM THE E AND DSNDING TO 50 HDG 300 DEGS FOR SEQUENCE AS #2 ARR. WITH BOTH PLANES POINTED AT EACH OTHER AND WAITING FOR RADAR W TO TURN ACFT X ONTO FINAL AND CONTINUE DSCNT DOWN TO 30 FOR THE VISUAL APCH TO RWY 17R; IT CAME TO MY ATTN THAT ACFT X WAS NO LONGER ON FREQ; NORDO. SO; I TOOK CORRECTIVE ACTION IN TELLING RADAR W THAT I WAS TURNING ACFT Y IN FRONT AND MAKE THIS ACFT #1 FOR LNDG ON RWY 17R AND FOR THEM NOT TO TURN THE ACFT X BACK INTO TFC IF HE CAME BACK UP ON FREQ. I THEN TURNED ACFT IN FOR APCH TO AVOID LOSS OF SEPARATION. IMMEDIATELY AFTER THAT; I OBSERVED THE ACFT X ACFT TURNING BACK TO THE ARPT AND DSNDING. WITH THAT; I IMMEDIATELY STOPPED ACFT Y DSCNT AND TURNED THE ACFT R TO A 350 DEG HDG; WHILE EXPLAINING TO HIM WHAT JUST HAPPENED AS TO AVOID FURTHER CONFUSION. AFTER INVESTIGATION; ACFT X WITHOUT DIRECTION INADVERTENTLY SWITCHED OVER TO THE TWR FREQ AND TOLD THE TWR CTLR THEY HAD THE ARPT IN SIGHT. AT THIS TIME THE TWR CTLR; WHO IS NOT RADAR CERTIFIED; ISSUED A VISUAL APCH WITHOUT CTL FOR TURNS FROM APCH AND THEN ISSUED A LNDG CLRNC TO ACFT X. INADEQUATE TRAINING/SEASONING OF THE TWR POS AT AUS IS PARTLY TO BLAME FOR THIS AIRSPACE DEV AND COULD HAVE LED TO A LOSS OF SEPARATION.