ACR X CLB THROUGH OCCUPIED ALT VISUAL SEPARATION BY CTR RECEIVED TCASII RA WITH ACFT Y.

Narrative

SHORTLY AFTER TKOF FROM BDL ENRTE TO PIT; WE WERE HANDED OFF TO ZBW. CLRNC WAS DIRECT TO CTR VOR. AT 11000 FT; WE WERE ADVISED OF TURBOPROP TFC AT '12000 FT; 1-2 O'CLOCK; APPROX 8 MI.' WE ACQUIRED THE TFC VISUALLY AND VIA TCASII AT 2 O'CLOCK AND ADVISED ATC. AT THIS POINT; ZBW ISSUED THESE INSTRUCTIONS: 'MAINTAIN VISUAL SEPARATION WITH THAT TFC; CLB AND MAINTAIN 17000 FT; NO DELAY THROUGH 13000 FT.' AFTER ACKNOWLEDGING THIS CLRNC; THE FO AND I DETERMINED BY VISUAL REFS AND THE TCASII THAT WE COULD INITIATE A QUICK CLB AND MAINTAIN SEPARATION; ALTHOUGH THE TFC WAS TRACKING STRAIGHT DOWN THE 2 O'CLOCK LINE OF THE TCASII. AFTER INITIATING THE CLB; THE TCASII ISSUED A TA; WHEREUPON THE FO; FLYING THE PLANE; INCREASED THE CLB RATE. THE TA WAS FOLLOWED QUICKLY BY AN INSISTENT RA ('DSND! DSND NOW!). SINCE WE WERE ALREADY COMMITTED TO A HIGH RATE OF CLB AT APPROX 20 DEG DECK ANGLE AND 5000 FPM RATE OF CLB AND TRADING AIRSPD FOR ALT FROM THE INITIAL 310 KTS; WE CONTINUED THE CLB AND MADE A CLRING TURN OF ABOUT 30 DEGS TO THE L OF OUR RTE CLRNC. FROM THE TCASII WE CONCLUDED THAT WE PASSED 12000 FT; THE TARGET'S ALT; AT APPROX 3.5 NM RANGE; AND CLRED 13000 FT AT ABOUT 3.0 NM RANGE. AIRSPD AT THE CONCLUSION OF THE EVASIVE MANEUVER WAS 230 KTS. THE OTHER TFC MADE NO APPARENT CHANGE IN FLT PATH OR ALT. THE TFC PASSED ALMOST DIRECTLY BELOW US. 1) ZBW WAS REMISS IN ISSUING THESE CLB INSTRUCTIONS -- THIS IS A TECHNIQUE ALLOWED FOR APCH/DEP CTL BUT NOT FOR ARTCC. 2) WE WERE MISTAKEN IN ACCEPTING THIS CLRNC; AND THEN IN INITIATING THE CLB WHICH RESULTED IN REDUCED SEPARATION. 3) IT IS ALWAYS DANGEROUS TO DISREGARD A TCASII RA; BUT UNDER VISUAL CONDITIONS WE WERE MORE COMFORTABLE DOING THIS THAN ATTEMPTING TO TRANSITION FROM A 5000 FPM CLB TO A 3000 FPM DSCNT. THE BIG PROB POTENTIAL IS THAT THE OTHER TFC WOULD HAVE BEEN ISSUED A 'CLB' RA WHICH WOULD HAVE FURTHER REDUCED SEPARATION. PRESUMABLY; THIS IS PRECISELY WHAT WOULD HAVE HAPPENED IF THE OTHER TFC HAD BEEN TCASII-EQUIPPED WITHOUT A VISUAL CONTACT ON US. SUPPLEMENTAL INFO FROM ACN 298009: WE WERE LEVEL AT 11000 FT NWBOUND ABOUT 10 NM SE OF CTR; AWAITING CLB CLRNC FROM CTR. CTR CALLS OUT TFC AT 2 O'CLOCK AND LEVEL AT 12000 FT WBOUND; I DON'T RECALL THE DISTANCE. WE ADVISED CTR WE HAD THE TFC IN SIGHT. CTR HESITATES FOR A MOMENT AND SAYS TO CLB TO 17000 FT AND NO DELAY THROUGH 13000 FT. WE CHK THE TFC; AND IT'S 6 MI NOW. WE BOTH FELT COMFORTABLE THAT IF WE EXPEDITED THE CLB; IT SHOULD BE NO PROB. I IMMEDIATELY ENGAGED CWS ON THE AUTOPLT AND STARTED A 5000-6000 FPM CLB. IMMEDIATELY AFTER I INITIATED THE CLB; TCASII DISPLAYED A TA ALERT. SOON AFTER; TCASII DISPLAYED AN RA; COMMANDING A DSCNT. SINCE I HAD THE TFC IN SIGHT; I KEPT THE ACFT CLBING THROUGH 12500 FT. WHILE TURNING L (WBOUND) TO GET MORE SPACING. I SAW THE COMMUTER TURBOPROP PASS BENEATH US AT ABOUT 13000 FT. THIS SIT WAS ONE OF THOSE LIVE AND LEARN AND TOO CLOSE FOR COMFORT. I'M NEVER GOING TO ACCEPT A CLRNC LIKE THAT AGAIN. I'M JUST GOING TO ADVISE THAT WE'LL WAIT FOR TFC TO CLR WHETHER WE HAVE THE TFC IN SIGHT OR NOT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: BOTH RPTRS INFORMED THE CTRS CAN NOW USE VISUAL SEPARATION BELOW FL180. THIS WAS EFFECTIVE IN FEB/XX/95.