LTSS BTWN 2 ACR ACFT. TCASII ALERT. OPERROR. EVASIVE ACTION.

Narrative

WHILE ON RADAR VECTORS FOR AN ILS APCH AT CMH (RWY 28) WE HAD AN RA ON THE TCASII WHICH WE FOLLOWED. THE SITUATION WAS AS FOLLOWS: ON A HDG OF 360 DEG ASSIGNED AT 4000 MSL (LEVEL) WE WERE ISSUED A HDG OF 300 DEG TO INTERCEPT THE ILS. AT THAT TIME WE SAW THE LNDG LIGHTS OF ANOTHER ACFT AT ABOUT 11 TO 11:30 POS AND THEY APPEARED TO BE CLOSING. WE ASKED APCH CTL WHO THE TFC WAS. THEY REPLIED THAT IT WAS ACR Y FOLLOWING US. AT THAT MOMENT THE TCASII GAVE US A TA ALERT. THE TFC WAS AT THE SAME ALT AS US AT 11:30 POS AND CLOSING. THE TCASII THEN CHANGED FROM A TA TO AN RA WITHIN SECONDS. THE TCASII INSTRUCTED US TO CLB WHICH WE DID AND AT THAT TIME CMH INSTRUCTED ACR Y TO TURN R IMMEDIATELY AND ALSO INSTRUCTED US TO DO THE SAME. BOTH ACFT COMPLIED. I FEEL THIS INCIDENT COULD HAVE BEEN AVOIDED IF APCH CTL HAD ISSUED US A TA BEFORE WE ASKED. TIME WAS WASTED ON COM. AT THIS POINT WE WERE CLOSING TOO FAST. I CALLED APCH CTL AFTER WE LANDED ON THE TELEPHONE. THEY EXPLAINED THAT WE WERE 2 1/2 - 3 MI APART (SAME ALT; OPPOSITE DIRECTION) WHEN WE WERE ISSUED TURN INSTRUCTIONS. (THE TCASII HAD ALREADY ISSUED AN RA ALERT BY THAT TIME.) I DON'T LIKE THE IDEA OF 2 ACFT BEING PUT ON A POSSIBLE COLLISION COURSE; SAME ALT IN A SMALL AREA SUCH AS THE APCH AREA. THAT LEAVES TOO MUCH TO CHANCE. A RADIO OR RADAR FAILURE OR ANY OTHER DISTR COULD CAUSE A MAJOR CONFLICT.