ACR MLG ALTDEV EXCURSION FROM CLRNC IN RESPONSE TO TCASII TA AT CRS ALT.

Narrative

THE PROBLEM HEREIN DESCRIBED AROSE BECAUSE OUR TCASII SYS INTERROGATED AN ONCOMING TRANSPONDER ON AN ACFT THAT WAS CLBING TO A CRUISE ALT 1000 FT BELOW OURS. WHILE THE ONCOMING TFC WAS CLBING; THE LEAD COMPUTED BY TCASII SHOWED THAT THAT TFC WOULD PASS ABOVE US. WE DID NOT HAVE VISUAL CONTACT UNTIL AFTER WE HAD BEGUN A DSCNT BASED ON THE TCASII RA TO DO SO. WE DSNDED IN COMPLIANCE WITH THE TCASII RA ONLY 200 FT AT WHICH TIME WE VISUALLY ACQUIRED THE TFC WHICH HAD JUST LEVELED AT FL280 AS PLANNED FOR IT. WE IMMEDIATELY CLBED BACK TO FL290 AND SIMULTANEOUSLY THE TCASII RA TERMINATED. WE BREACHED THE 1000 FT SEPARATION BY 200 FT. A MAJOR CONTRIBUTOR TO THIS INCIDENT IS THE LEAD COMPUTING FEATURE OF TCASII WHICH IS BASED ON THE CLB OR DSCNT. FLT GUIDANCE EQUIPPED ACFT SHOULD HAVE THE CAPABILITY OF USING THE SELECTED ALT TO INPUT INFO TO THE TRANSPONDER TO SHOW INTERROGATING TCASII THAT THEY WILL HAVE PROPER SEPARATION AT LEVEL OFF. SUPPLEMENTAL INFO FROM ACN 200444: CONTACTED FT WORTH SECTOR CTR PER THEIR REQUEST UPON LNDG DFW. CAPT STATED THAT FT WORTH SHOWED SEPARATION OF 2 1/2 MI HORIZ AND APPROX 600 FT VERT.