ZMP CONTROLLER DESCRIBED EVENT WHEN AIRCRAFT REQUESTED LOWER ALTITUDE WITHOUT STATING REASONS; WAS INITIALLY DENIED BECAUSE OF TRAFFIC BUT LATER GIVEN DESCENT WHEN CONTROLLER SENSED EMERGENCY SITUATION; ICING CONDITIONS CAUSED EVENT.

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SR22 PLT NEEDED LOWER ALT DUE TO UNKNOWN REASONS. TFC PROHIBITED DSCNT CLRNC BUT A TURN FOR TFC WAS ISSUED. URGENCY IN PLT'S VOICE INDICATED EMER SITUATION. ATC OBSERVED DSCNT AND CONFLICT WITH TFC AT 5000 FT. NO DSCNT CLRNC WAS ISSUED. ATC MOVED TFC AT 5000 FT TO 4000 FT IMMEDIATELY UPON SR22 REQUEST FOR LOWER. EMER/PLTDEV. THE INCIDENT WAS HANDLED APPROPRIATELY BY ATC WHEN ATC MOVED THE TFC IMMEDIATELY UPON SENSING URGENCY IN SR22'S VOICE. SUPPLEMENTAL INFO FROM ACN 810126: I WAS ENRTE IN AN SR22/G AT 6000 FT. IMC; RAIN INCREASING FROM -4 TO MODERATE RAIN. OUTSIDE AIR TEMP DROPPING FROM +1 TO -2 DEGS C. NEXRAD FAILED 10 MINS EARLIER. WX DETERIORATING RAPIDLY. TKS AND PITOT HEAT ON. INDICATIONS OF CLEAR ICE FORMING AFT OF LEADING EDGE IN IRREGULAR PATTERN. AIRSPD DECAY OF 5 KTS. HVY RADIO TFC. MADE NUMEROUS ATTEMPTS TO BREAK IN TO REQUEST IMMEDIATE DSCNT TO 5000 FT FROM 6000 FT. CTLR REPLIED SHE WAS UNABLE. TOLD HER I NEEDED IMMEDIATE DSCNT AND DESCRIBED WX CONDITIONS. SHE REPLIED SHE COULD GIVE ME A VECTOR AND 5000 FT. I ACCEPTED. SHE GAVE ME A HDG OF 330 DEGS AND (I THOUGHT SHE CLRED ME TO 5000 FT). I TOOK ASSIGNED HDG AND BEGAN DSCNT. SHE CALLED INDICATING SHE DID NOT CLEAR ME TO 5000 FT. I WAS NEVER ASKED WHAT THE NATURE OF THE PROB WAS. I DID NOT DECLARE AN EMER BECAUSE I THOUGHT I COULD GET LOWER. I HAD TO CHK FOR ICE ACCRETION; TURN OFF THE AUTOPLT TO MANUALLY FLY THE ACFT; CONFIRM LACK OF NEXRAD DATA; COMMUNICATE/NEGOTIATE WITH ATC. I SHOULD HAVE DECLARED AN EMER AS SOON AS I SAW THE ICE. I THOUGHT I DID AND COULD NOT UNDERSTAND WHY THE CTLR WOULD NOT ALLOW ME TO DSND. I MAY NOT HAVE HELD THE PUSH-TO-TALK SWITCH HARD ENOUGH OR LONG ENOUGH. SUPPLEMENTAL INFO FROM ACN 810327: PLT REQUESTED AN IMMEDIATE DSCNT TO 5000 FT AND DID NOT STATE REASON. I MONITORED THE CTLR GIVE AN OPPOSITE DIRECTION TURN AND ISSUED TFC. PLT STARTED DSCNT TO 5000 FT AND WAS TOLD TO MAINTAIN 6000 FT. I WAS MONITORING FROM A POS RELIEF BRIEFING.