A C182 PLT HAS AN NMAC DURING A SPIRALING DSCNT AFTER 'JUMPERS AWAY' WITH AN UNKNOWN C172 WHO WAS NOT ON THE LCL CTAF OR ATC CTR FREQ.

Narrative

AFTER RELEASING JUMPERS AT 12000 FT MSL; I BEGAN MY TYPICAL DSCNT OVER OSAGE CITY ARPT (140 KTS; 45-60 DEGS BANKED SPIRAL). I WAS IN CONTACT WITH AN ACFT INBOUND TO 53K AND ANNOUNCED JUMPERS WERE CLR AND MY LOCATION AND ALT. I ALSO ANNOUNCED TO ZKC THAT JUMPERS WERE CLR. AS I DSNDED BELOW 6000 FT I NOTICED ANOTHER ACFT IN LEVEL FLT APCHING FROM THE SW; APPROX 200-300 FT BELOW ME AND CONVERGING ON ME. I STEEPENED MY R BANKING TURN TO AVOID THIS ACFT. THE OTHER ACFT ALSO TURNED R TO AVOID MY ACFT. AFTER THIS ENCOUNTER; I APCHED THE ACFT FROM BEHIND AND TO THE R TO ACQUIRE THE N-NUMBER. I IDENTED THE OTHER ACFT. I MADE SEVERAL ATTEMPTS TO CONTACT THIS ACFT ON THE LCL FREQ. NO CONTACT WAS MADE AND THE ACFT FLEW NBOUND TOWARDS TOPEKA. I WAS NEVER ALERTED TO THIS ACFT BY ZKC. THIS ACFT FLEW DIRECTLY OVER THE DROP ZONE AND WAS NOT MONITORING THE LCL AREA (122.9). ATC NEVER ALERTED ME TO A PRIMARY TARGET IN MY AREA PRIOR TO THE JUMP. THERE WERE NO FACTORS IMPAIRING MY JUDGEMENT OR PERCEPTION OTHER THAN MY BANKING TURN ON THE DSCNT. I FEEL I DID EVERYTHING WITHIN REG AND FOLLOWED PROC. THIS SIT COULD HAVE BEEN PREVENTED IF THE OTHER ACFT WAS MONITORING THE LCL FREQ AND IF ATC WOULD HAVE TOLD ME OF AN ACFT IN PROX OF THE DROP ZONE.