AN ACR MLG IGNORED HIS TCASII INSTRUCTIONS AS HE WAS BEING GIVEN URGENT AND CONTRADICTORY INSTRUCTIONS BY TRACON.

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THIS NARRATIVE DEALS WITH A TCASII RA RECEIVED WHILE ON APCH. ON A L BASE LEG AT 5000 FT; UNDER RADAR VECTORS; WE RECEIVED A TCASII TA WHICH RAPIDLY BECAME A TCASII RA. THE CONFLICTING TFC APPEARED TO BE AHEAD AND LEVEL AT OUR ALT. THE RA COMMANDED 'DSND; DSND!' WE BEGAN A DSCNT AND WERE AT 4900 FT WHEN ATC GAVE US A TA; A R TURN TO 350 DEGS; THEN AN IMMEDIATE R TURN TO 350 DEGS AND CLB TO 6000 FT. WE ADHERED TO ATC'S INSTRUCTIONS EVEN THOUGH THE TCASII WAS TELLING US TO DSND. THIS WAS A VERY STRESSFUL MANEUVER FOR THE CREW. THE TCASII THEN INSTRUCTED US TO 'CLB' THEN SHORTLY FOLLOWED BY ANOTHER 'DSND;' THEN 'MONITOR VERT SPD;' TO 'CLR OF CONFLICT.' THE ENTIRE EVENT TOOK APPROX 30-45 SECONDS. WE ELECTED TO CLB GIVEN THE CTLR'S INSTRUCTION AND GIVEN OUR CURRENT ALT; WERE UNCERTAIN OF TERRAIN CLRNC HAD TCASII CONTINUED THE DSCNT COMMAND. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTING CAPT IS SURE THAT THIS WAS NOT A FALSE ALARM. SOMETIME DURING THIS INCIDENT; THE APCH CTLR SAID SOMETHING LIKE 'ONE GOT AWAY FROM US ON THE OTHER SIDE.' CVG WAS LNDG ON PARALLEL RWYS 18 AND AN ACFT THAT WAS TO LAND ON RWY 18R FAILED TO TURN WHEN REQUESTED; PUTTING 2 ACFT HEAD-TO-HEAD. THE RPTR BELIEVES THAT HIS TCASII WAS WORKING PROPERLY. THE RPTR FINDS THAT TCASII CAN BE A NUISANCE AT TIMES. THE RPTR'S ACR FLT MANUAL SUGGESTS THAT THE FLCS CAN IGNORE TCASII WHEN IT IS APPARENT THAT ATC HAS A GOOD HANDLE ON THE TFC SIT AS IN THIS CASE.