A TRANSITIONING C182 IN MCI CLASS B BEING CTLED BY MCI APCH HAS AN NMAC WITH AN MD80 CLBING OUT OF MCI ARPT.

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THE INCIDENT OCCURRED WHILE TRANSITIONING THROUGH CLASS B AIRSPACE OVER KANSAS CITY DURING A VFR FLT. UPON CLRNC INTO CLASS B; I WAS VECTORED FROM 170 DEGS TO 190 DEGS. AFTER APPROX 10 MINS; I WAS VECTORED TO 180 DEGS. AT THAT TIME; I REQUESTED AND WAS GRANTED AN ALT CHANGE FROM 5500 FT MSL TO 7500 FT MSL FOR MORE FAVORABLE WIND. WITHIN APPROX 5 MINS AFTER THAT I WAS 'CLRED ON COURSE.' SHORTLY THEREAFTER (APPROX XA15) MCI APCH ADVISED OF TFC AT MY 9 O'CLOCK POS. THE MD80 WAS DEPARTING MCI AND GIVEN A SIMILAR TFC NOTIFICATION AS TO MY POS. BOTH PLTS ACKNOWLEDGED THE NOTIFICATION. IT WAS DARK (OR VERY NEARLY DARK) AT THE TIME OF THE INCIDENT. I BEGAN SCANNING BUT DID NOT SEE THE ACFT AGAINST THE CITY LIGHTS; UNTIL WE WERE APPROX 1 MI APART. THE MD80 APPEARED TO BE CLBING AND IT LOOKED AS THOUGH WE WERE ON A COLLISION COURSE. BEING THE ACFT TO THE OTHER'S R; I EVALUATED MY SIT AND DETERMINED THAT AN IMMEDIATE DSCNT WAS THE ONLY WAY TO AVOID A MIDAIR COLLISION. GIVEN OUR COURSES; PROX; AND SPDS; IT DID NOT APPEAR THAT A TURN TO THE R WOULD CLR ME FROM HIS COURSE. GIVEN THE APPEARANCE OF THE MD80'S INCREASING ALT; I SURMISED THAT I COULD NOT CLB FAST ENOUGH TO GET ABOVE ITS FLT PATH. DESPITE THE DANGER OF WAKE TURB; MY ONLY COURSE OF ACTION WAS TO DSND IMMEDIATELY TO AN ALT THAT WOULD; WITHOUT QUESTION; CLR ME BENEATH THE OTHER ACFT. THEREFORE; I NOSED OVER TO ATTAIN 6900 FT MSL OR BELOW; AS QUICKLY AS POSSIBLE. THE OTHER PLT INITIATED A TURN TO THE L BASED ON A TCASII WARNING BUT DID NOT MAKE MENTION OF ACTUALLY SEEING ME UNTIL AFTER DOING SO. I WAS USING STROBE; BEACON; AND NAV LIGHTS AT THE TIME AND SHOULD HAVE BEEN HIGHLY VISIBLE AGAINST THE NIGHT SKY. IN MY RECOLLECTION IT WAS NEVER MADE CLR BY ATC THAT THE MD80 WAS CLBING OR LEVEL. NOR WAS IT MADE CLR THAT THE ACFT WOULD PASS UNDER ME OR THAT WE HAD PROPER SEPARATION. HAD THIS BEEN THE CASE; I WOULD NOT HAVE INITIATED THE DSCNT. I HAVE REQUESTED A COPY OF THE RADAR TAPES FROM MCI TO BETTER UNDERSTAND THE SPECIFIC CIRCUMSTANCES.