A320 CAPTAIN; WHILE MAINTAINING VISUAL SEPARATION; REPORTS NMAC WITH AN F16 AT 16000 FEET 30 NM WEST OF DTW.

Narrative

LEVEL AT 16000 FT; ZOB ASKED IF WE WERE VMC ON TOP; THE FO ANSWERED WE WERE. (IT WAS ACTUALLY A VERY CLR NIGHT.) ATC THEN INFORMED US WE HAD 2 F16'S AT OUR 2 O'CLOCK POS APPROX 15 MI. (I DON'T RECALL THE ACTUAL PHRASEOLOGY ATC USED IN RELATION TO THEIR ALT OTHER THAN THAT THEY WERE ABOVE OUR ALT.) WE OBTAINED THE VISUAL ON THE TFC BTWN 10-12 MI AS WELL AS A TCAS INDICATION SHOWING THE TFC ABOUT 1000 FT ABOVE OUR ALT (17000 FT). I DIRECTED THE FO TO INFORM ATC WE HAD A VISUAL ON THE TFC; WHICH HE DID. ATC THEN CLRED US TO MAINTAIN VISUAL SEPARATION WITH THAT TFC AND TO CLB AND MAINTAIN FL230. WITH MY CONCURRENCE THE FO ACKNOWLEDGED THE CLRNC. I INSERTED FL230 INTO THE FCU; SELECTED 'OPEN' CLB. AS OUR ACFT STARTED TO CLB; THE TFC WAS ABOUT 6 MI AND APPEARED TO BEGIN A DSCNT. I RECEIVED A TCAS TA THAT ALMOST INSTANTLY CHANGED TO AN RA 'DSND; INCREASE DSCNT.' UPON RECEIVING THE RA; WE HAD ASCENDED ABOUT 200-300 FT AND WERE BTWN 167200-16300 FT. I IMMEDIATELY BEGAN A PUSHOVER TO DSND WHEN THE RA CHANGED TO 'CLB; CLB NOW' AND WAS INDICATING A MAX CLB RATE REQUIRED. I REVERSED MY DSCNT TO A CLB AND WITHIN A COUPLE SECONDS AN F16 PASSED DIRECTLY UNDER THE ACFT FROM R TO L. THE FO SAW IT AND SAID HE HEARD IT. I WAS MONITORING THE TCAS AND SAW THE ALT SEPARATION DECREASE TO 200 FT. FROM THE BEGINNING OF THE CLB FROM 16000 FT THROUGH THE RA MANEUVERS UNTIL PASSING THE F16; I DON'T BELIEVE WE ASCENDED OR DSNDED MORE THAN 300 FT DUE TO THE RAPID CHANGE IN DIRECTION OF THE RA FROM DSCNT TO CLB. THE F16 PASSED BELOW US AT ABOUT 16000 FT IS MY BEST GUESS. THE F16'S WERE ON ANOTHER FREQ OR ON UHF; WE DID NOT KNOW THE CLRNC RECEIVED BY THE F16'S. I BELIEVE A FEW ITEMS COULD HAVE PREVENTED THIS OCCURRENCE: 1) THE FACT THAT BOTH ACFT WERE NOT ON THE SAME FREQ REDUCED SITUATIONAL AWARENESS OF THE INTENTIONS AND CLRNCS OF ALL ACFT INVOLVED. I ASSUME THE F16'S WERE ON UHF WITH US ON VHF WITH THE CTLR NOT SIMULCASTING ON BOTH RADIOS. 2) THERE WAS NO OPERATIONAL NECESSITY TO ASSUME VISUAL SEPARATION AT NIGHT WITH CONVERGING TFC. MAINTAINING IFR SEPARATION WITH ATC WOULD HAVE BEEN MUCH SAFER; ESPECIALLY AT NIGHT NOT HAVING THE VISUAL REFS YOU WOULD DURING DAYLIGHT. 3) ONCE DECLARING WE HAD THE VISUAL WITH THE TFC (WE HAD THEIR LIGHTS AT BTWN 10-12 MI) FOR ATC TO GIVE US CLRNC AND US TO ACCEPT A CLRNC TO CLB AT NIGHT THROUGH THEIR ALT IS AN UNSAFE PROC WITH CONVERGING TFC THAT WILL MEET WITHIN 1 MIN. THIS WAS ESPECIALLY COMPOUNDED BY NOT HAVING THE SITUATIONAL AWARENESS OF THE RADIO XMISSIONS; CLRNCS AND INTENTIONS OF THE OTHER ACFT. 4) BOTTOM LINE: I DON'T SEE ANY OPERATIONAL NECESSITY FOR AN ACR TO ACCEPT VISUAL SEPARATION AT NIGHT FROM OTHER ACFT EXCEPT POSSIBLY IN THE ATA WHERE THE RTE OF FLT AND ALTS ARE KNOWN.