AN IFR ACFT DSNDING IN IMC TAKES EVASIVE ACTION BASED ON ITS SKY WATCH UNIT TO AVOID A CLBING VFR ACFT; THAT HAD BEEN RPTED BY THE APCH CTLR; BY AN ESTIMATED 100 FT.

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SHORTLY AFTER BEING HANDED OFF TO ASHEVILLE APCH; WE RECEIVED CLRNC TO DSND. JUST PRIOR TO RECEIVING THAT CLRNC WE WERE GIVEN A TA BY ASHEVILLE APCH STATING AN ACFT OUT OF 7100 FT WOULD BE CLBING TO 8500 FT AND THAT THE TFC WAS LOCATED AT APPROX OUR 11 O'CLOCK POS AT THE TIME. I BELIEVE HE STATED THE TYPE OF ACFT AS SOME TYPE OF SINGLE ENG BUT I CANNOT BE SURE OF THAT. WE ADVISED HIM WE HAD 'NO CONTACT' WITH THE TFC. APPROX 2-3 MINS LATER WE WERE GIVEN CLRNC TO DSND OUT OF OUR PRESENT ALT DOWN TO 7200 FT AND GIVEN A HDG OF 150 DEGS WHICH WAS SLIGHTLY R OF OUR PRESENT COURSE. THE CAPT INITIATED THE DSCNT AND SELECTED THE 150 DEG HDG AS INSTRUCTED. OUT OF APPROX 8500 FT; OUR SKYWATCH UNIT SHOWED TFC SLIGHTLY TO THE L OF US AND AT APPROX 300 FT BELOW. BEFORE I COULD QUERY ATC ON THE TFC; THE SKYWATCH UNIT BEGAN TO GIVE AN AUDIBLE WARNING OF THE TFC. THE CAPT STOPPED THE DSCNT; LEVELING OFF AT 8100 FT; AND TURNED TO THE R IN AN ATTEMPT TO AVOID A COLLISION. WE DID NOT HAVE THE ACFT IN SIGHT AT THE TIME AND FLT CONDITIONS WERE IMC. OUR ESTIMATE ON 'DISTANT MISSED' IS BASED SOLELY OFF THE SKYWATCH INFO. BOTH THE CAPT AND I KNOW THAT A MANEUVER BASED SOLELY ON THE INFO PROVIDED BY SKYWATCH IS NOT PREFERABLE; BUT GIVEN THE KNOWLEDGE OF THE OTHER ACFT NEAR OUR POS BOTH OF US FELT THE ACTIONS JUSTIFIED. I FEEL THAT ALLOWING THE OTHER ACFT TO CLB WITHOUT US HAVING VISUAL REF TO IT WAS A FACTOR IN THIS CASE. ADDITIONALLY; I BELIEVE THE CTLR MAY NOT HAVE KNOWN THE FLT CONDITIONS THAT WE WERE IN AT THE TIME (WE DID NOT STATE WE WERE IN IMC). I BELIEVE IN THIS CASE IT WOULD HAVE BEEN APPROPRIATE FOR ATC TO DELAY OUR DSCNT UNTIL THE TFC WAS EITHER IN SIGHT OR CLR OF OUR POS/PATH. LASTLY; IT WOULD HAVE BEEN HELPFUL IF I WOULD HAVE ASKED FOR ADDITIONAL INFO ON THE TFC'S POS AS WE STARTED OUR DSCNT. SUPPLEMENTAL INFO FROM ACN 593179: OUR SKYWATCH UNIT SHOWED US CONVERGING TFC CLBING AT THE 11 O'CLOCK POS. CTLR ASKED US WHY WE TURNED INTO THE VFR TFC. WE TOLD CTLR THAT WE TOOK EVASIVE ACTION.