FLC OF A CANADAIR REGIONAL JET CL65 TURNED AND CLBED IN RESPONSE TO TCASII RA WARNING OF A CONFLICTION WITH OTHER TFC. A SINGLE ENG CESSNA WAS OBSERVED GOING PAST THEIR ACFT AT 100 FT LOWER; AND 2000 FT LATERALLY; RIGHT WHERE THEY WERE PREVIOUSLY.

Narrative

CTR HANDED US OFF TO GRB APCH. GRB GAVE US DSCNT TO 3000 FT MSL AND HDG (APPROX 015 DEGS) VECTORS TO VISUAL RWY 24 AT GRB. I ALWAYS USE THE TCASII 10 NM DISPLAY ON THE MFD WHEN IN APCH/DEP PHASE OF FLT; ALTHOUGH NOT REQUIRED BY COMPANY POLICY. WHILE LEVEL AT 3000 FT MSL; I OBSERVED A TARGET ON THE TCASII DISPLAY AT 10 NM AND 1 O'CLOCK POS FROM US ON WHAT I PERCEIVED TO BE ON AN INTERSECTING COURSE WITH US. I TOLD THE PF CAPT AND HE SAID 'OH; OK.' I CONTINUED TO MONITOR THE SCREEN AND SCAN OUTSIDE FOR THIS TFC. WE WERE INDICATING 180 KIAS AT THAT TIME. I WAS NOT ABLE TO VISUALLY ACQUIRE THE TFC. I TOLD THE CAPT AGAIN AND HE APPEARED UNCONCERNED I THINK BECAUSE HE FELT WE WERE ON AN IFR FLT PLAN; OPERATING IN CLASS C AIRSPACE AND WERE THE ONLY ACFT THE CTLR APPEARED TO BE WORKING (IT WAS SLOW). AT 5 NM FROM US; I COULD STILL NOT VISUALLY SEE THE RAPIDLY CLOSING TARGET AND REDUCED THE RANGE ON MY TCASII SCREEN TO 5 NM AND TOLD THE CAPT 'I CAN'T SEE THIS GUY (THE OTHER TFC WAS AT 3000 FT MSL THE ENTIRE TIME) BUT WE NEED TO TURN L.' THE CAPT LOOKED AT HIS 5 NM TCASII DISPLAY THEN; AND I SAID 'TURN L; STILL DON'T HAVE A VISUAL.' THE CAPT TURNED L APPROX 20 DEGS AND STARTED A SHALLOW CLB BASED ON OUR OBSERVATION OF THE TCASII SCREEN. APPROX 15 SECONDS LATER WE GOT AN RA 'MONITOR VERT SPD.' WE CONTINUED THE EVASIVE ACTION THAT WE HAD STARTED PRIOR TO THE RA (IT COINCIDED WITH THE MVS RA COMMAND). AT APPROX 3100 FT AND 20 DEGS L OF THE ORIGINAL VECTOR; I SAW THE TFC PASS OUR 4 O'CLOCK 100 FT BELOW AND 2000 FT AWAY. THE TCASII NEVER GAVE A PRELIMINARY 'TFC WARNING.' WE WERE BOTH PUZZLED BY THIS. THE CAPT AND I AGREED THAT IF I HAD NOT HAD THE TCASII SCREEN UP ON THE MFD OR IF THE TCASII HAD BEEN DEFERRED (LEGAL; BUT STUPID) THAT WE WOULD HAVE COLLIDED WITH THE OTHER ACFT (HIGH WING CESSNA SINGLE). THE CTLR NEVER CALLED THE TFC TO US UNTIL WE WERE IN THE RA. SHE SAID IT WAS A PRIMARY TARGET ONLY AND THAT SHE JUST GOT IT ON HER SCREEN. I TOLD HER WE WERE EXECUTING AN RA. AFTER THE RA I ASKED HER IF THE ACFT WAS IN HER AIRSPACE AND SHE SAID YES. AFTER LNDG; I CALLED THE GRB TRACON SUPVR AND HE SAID THAT THEY WERE NOW TRACKING THE ACFT ON RADAR AND THAT IT HAD ENTERED THE GRB CLASS C AIRSPACE WITHOUT A CLRNC. HE COULD NOT EXPLAIN WHY WE HAD THE ACFT ON TCASII AND THEY COULDN'T SEE IT ON THEIR RADAR AND THEN AS A PRIMARY ONLY. TCASII SHOULD BE A REQUIRED; NON-DEFERRABLE ITEM. THIS TCASII SAVED MANY LIVES.