ACR RESPONDING TO TCASII RA CAUSES LTSS WITH A TCA SMA ACFT.

Narrative

SMA X WAS CLRED INTO THE TCA FROM THE NE TO THE SW AT 6500 FT. ACR Y WAS DSNDING TO 5000 FT. ACR Y'S PATH WAS GOING TO TAKE HIM BEHIND SMA X ON I TS DSCNT. ACR X'S TCASII ALERTED THE PLT THAT TFC WAS AHEAD AND THE PLT RESPONDED TO THE TCASII BY CLBING BACK TO 7200 FT. AS ACR Y LEVELED AND CLBED; IT GAINED HORIZLY ON SMA X. SEPARATION WAS THEN LOST AND PLT FILED A NEAR MISS. IF ACR Y WOULD HAVE CONTINUED HIS NORMAL DSCNT HE WOULD HAVE PASSED WELL BEHIND AND BELOW OF SMA X. RESPONDING TO THE TCASII CREATED THE SITUATION. THE PLT DID NOT ADVISE THE CTLR OF HIS ACTIONS UNTIL HE WAS LEVELING AT 7200 FT. THE CONCEPT OF TCASII IS GOOD; BUT ITS APPLICATIONS CAN CREATE A REAL HAZARD TO FLT SAFETY. ACR Y ALMOST RAN OVER SMA X BECAUSE OF ITS ACTIONS. SUPPLEMENTAL INFO FROM ACN 216550: WHILE IN CONTACT WITH MSY APCH CTL WE RECEIVED A TCASII WARNING. OUR POS WAS 13 NM ENE OF THE MSY VOR DSNDING TO 5000 FT. PASSING THROUGH 6500 FT WE RECEIVED AN AURAL AND VISUAL TCASII WARNING. THE TARGET WAS VERY CLOSE HORIZ AND APPROX 200 FT BELOW US. THE FO IMMEDIATELY FOLLOWED THE TCASII EVASION INSTRUCTIONS TO CLB. THE SMALL HIGH WING ACFT FINALLY BECAME VISUAL TO US AT A DISTANCE OF LESS THAN 1/2 MI FROM US AT APPROX 6000 FT. WERE IT NOT FOR THE TCASII WARNING WE WOULD HAVE HAD A NEAR MISS AT BEST. THE TARGET DID NOT SHOW UP ON OUR TCASII UNTIL WE WERE EXTREMELY CLOSE AND APCH APPARENTLY DID NOT SEE HIM UNTIL WE WERE OUT OF DANGER.