AN EMB120 IN DSCNT 33 MI SE OF TTT ALMOST COLLIDES WITH A C172 NEBOUND AT 5500 FT. RPTR STATES THAT ZERO FT VERT SEPARATION WAS CHANGED TO 500 FT BY THE EVASIVE ACTION CLB. PIC CITES ATC APCH CTL PROC AS CAUSAL. DFW; TX.

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DFW WAS IN NORTH FLOW. FLT WAS ASSIGNED THE CEDAR CREEK 4 (CQY.CQY4) ARR. FLT WAS DSNDING THROUGH 6000 FT TO ASSIGNED ALT OF 5000 FT. FLT WAS UNDER DFW APCH CTL AT 33 DME FROM MAVERICK (TTT) VOR. ATC ISSUED A TA AT THE SAME TIME TCASII ALERTED. VISUAL SEARCH PRODUCED A C172 ON A COLLISION COURSE AT 5500 FT. THE FLT'S DSCNT WAS STOPPED AND AN EVASIVE CLB BEGUN. MISS DISTANCE WAS ZERO HORIZ AND WOULD HAVE BEEN ZERO VERT IF EVASIVE ACTION HAD NOT BEEN TAKEN. THERE WOULD HAVE BEEN A COLLISION! ATC WAS ADVISED OF NEAR MISS AND AN NMAC WAS FILED WITH DFW TRACON WATCH SUPVR. THE DIRECT CAUSE OF THE NEAR MISS IS THE DFW ARR PROC DESIGN. TURBOPROP ACRS ARE DSNDED THROUGH VFR CRUISING ALTS JUST OUTSIDE THE CLASS B AIRSPACE WHERE MANY GA ACFT ARE CIRCUMNAVING THE AIRSPACE. DFW TRACON NEEDS TO REDESIGN THE TURBOPROP ARRS BEFORE A FATAL MIDAIR HAPPENS -- NOT AFTER! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ZFW HANDS THE ACFT OFF TO APCH CTL AT 40 DME WHERE APCH SENDS THE TURBOS DOWN TO 7000 FT AND THEN 5000 FT; INTO VFR GA TFC OVER 30 MI OUT. THE LCL UNION HAS APCHED THE DFW 530 OFFICE (PLANS AND PROCS) AND THEY ARE NOT INCLINED TO CHANGE PROCS; IMPLYING THAT THE JETS GET PREFERENCE TO THE HIGHER ALTS. RPTR STATED THAT THE TURBOPROPS CAN COMPLY WITH ANY RESTRS NEEDED AND SHOULD BE KEPT ABOVE THE 10000 FT LEVEL UNTIL WITHIN THE 30 MI ARC OF DFW. HE FURTHER STATED THAT ZTL HAS A WORKING MODEL WHERE THIS IS DONE WITH THE JETS 1000-2000 FT ABOVE. THE USE OF SPDS OF 250 KTS IS NOT A PROB FOR EITHER TYPE ACFT. THE RPTR IS A PLT UNION SAFETY REPRESENTATIVE FOR THE DFW REGION; A PROJECT TEAM MEMBER. THE DFW ARPT AND ATC PROC HAS A 'RED STAR' FROM THE UNION AND; IN THE RPTR'S OPINION; ATC SEEMS TO BE TRYING FOR A BLACK STAR. THE UNION IS ATTEMPTING TO BUILD A DATABASE OF THESE EVENTS. THE RPTR KNOWS OF SEVERAL INCIDENTS OF NMACS ATTRIBUTED TO THIS PROC. THE RPTR MADE CERTAIN THAT THE LCL FSDO OF THE FAA GOT THE COPY OF THE NMAC RPT.