PIPER 46; MALIBU PLT; ENCOUNTERS ICING DURING CLB AND IS UNABLE TO REACH ASSIGNED ALT. CTR CTLR DOES NOT RESPOND TO DSCNT REQUEST FAST ENOUGH FOR THE RPTR. HE STARTED A TURN AND DSCNT WITHOUT CLRNC. CTR THEN HANDLED HIS SIT WELL.

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EBOUND AT FL190 IN VMC APCHING N TO S FRONT AND LINE OF CLOUDS WITH TOPS AROUND FL200. OAT WAS -11C. REQUESTED CLB TO FL210 FROM ZKC. (2 REQUESTS/NO ANSWER/APPROX 2 MINS ELAPSED.) THIRD REQUEST WAS ANSWERED WITH A FREQ CHANGE TO ZAU. MADE REQUEST OF ZAU AT CHK-IN TO CLB TO FL210. CLB CLRNC WAS GRANTED AFTER A BRIEF 'STANDBY' (ADDITIONAL 2 MINS ELAPSED -- GND SPD WAS 230 KTS). AT START OF CLB I HAD ALREADY ENTERED CLOUDS AND JUST STARTED TO PICK UP ICE. THE ACFT CLBED SLOWLY TO ABOUT FL205 DURING WHICH TIME I RAPIDLY ACQUIRED MODERATE TO SEVERE MIXED ICE (APPROX 3 MINS). I WAS CLOSE TO THE TOPS BUT DID NOT BREAK OUT. ALL ANTI-ICE EQUIP HAD BEEN TURNED ON PRIOR TO ENTERING CLOUDS. DEICE BOOTS WERE CYCLED AND WORKED PROPERLY BUT LARGE CHUNKS OF ICE REMAINED ABOVE AND AFT OF THE LEADING EDGES. AIRSPD HAD DROPPED FROM 150 KTS TO 120 KTS. I COULD NOT GET FULL PWR DUE TO PREVIOUS SELECTION OF ALTERNATE INDUCTION AIR AND PROBABLE INDUCTION ICING. I TOLD CTR I COULD NOT CLB OR HOLD AIRSPD AND REQUESTED IMMEDIATE DSCNT AND 180 DEG TURN TO GET OUT OF THE WX AND ICING. CTR WAS VERY BUSY AND STARTED TO QUESTION ME IF I WANTED TO RETURN TO MY ARPT OF ORIGIN OR LAND IMMEDIATELY. THIS WAS TAKING TOO LONG SO I ADVISED CTR I WAS STARTING A L 180 DEG TURN AND BEGINNING A DSCNT. THIS WAS NECESSARY (ALTHOUGH NOT EXPLAINED TO CTR AT THE TIME) BECAUSE I WAS CONTINUING TO ICE AND LOSE AIRSPD. ALTERNATE INDUCTION AIR IN THE MALIBU REQUIRES A MINIMUM OF 130 KTS TO PREVENT INTAKE LOUVER ICING. CTR THEN CLRED ME TO TURN 90 DEGS TO A HDG OF 360 DEGS AND TO DSND TO 6000 FT AND ADMONISHED ME FOR STARTED A TURN AND DSCNT WITHOUT A CLRNC. CTR WAS VERY HELPFUL FROM THEN ON AND REQUESTED A MORE DETAILED RPT OF THE ICING ENCOUNTER AND BEGAN TO ADVISE OTHER ACFT. I CONTINUED TO DSND; REQUESTED 11000 FT AND CHANGED MY DEST TO PEORIA. ICE WAS SHED AND THE REMAINDER OF THE FLT WAS UNEVENTFUL ALTHOUGH IMC TO A LOW ILS AT PEORIA. CHAIN OF EVENTS/HUMAN PERFORMANCE COMMENTS: FLYING IN THIS ENVIRONMENT ALWAYS CONTAINS RISK OF ICE. IN RETROSPECT; IT WOULD HAVE BEEN BETTER TO DSND INTO THE CLOUDS TO BELOW THE FREEZING LEVEL (APPROX 12000 FT) THAN TO TRY TO CLB ABOVE THE CLOUDS ONLY 2000 FT HIGHER. I WAS NOT ABLE TO GET ON TOP DUE TO LIMITED PWR AND SEVERE ICING. THIS ICING ENCOUNTER WAS SEVERE AND VERY FAST. I HAVE CONSIDERABLE WX AND ICING EXPERIENCE AND I TOOK THESE ACTIONS BASED ON THAT EXPERIENCE AND THE UNUSUAL SEVERITY OF THIS ICING ENCOUNTER. IT IS POSSIBLE THAT I COULD HAVE CONTINUED AHEAD IN THE ICING WITHOUT TURNING OR DSNDING AS QUICKLY AS I DID. I DID NOT DECLARE AN EMER BECAUSE I GOT THE ACTION I NEEDED. AFTER CLRING ME TO TURN AND DSND; CTR ASKED ME IF I WANTED TO DECLARE AN EMER. AT THIS POINT; ICE ACCUMULATION HAD STOPPED AND I WAS ABLE TO MAINTAIN A SAFE AIRSPD IN THE DSCNT. PERHAPS IT WOULD HAVE BEEN BETTER TO DECLARE AN EMER BUT THE FLT ACTION I TOOK WOULD HAVE BEEN THE SAME. SINCE I WAS IN CONSTANT COM WITH CTR; I DON'T KNOW IF THIS WOULD HAVE CHANGED THEIR ACTIONS. I HAVE A GREAT RESPECT FOR ATC AND DO NOT TAKE THIS SIT AND MY ACTIONS LIGHTLY. AS FAR AS I KNOW; THERE WAS NO CONSEQUENCE TO OTHER ACFT EXCEPT THE KNOWLEDGE OF THE SEVERE ICING CONDITIONS AT MY ALT. I WILL DISCUSS THIS SIT WITH MY FLT INSTRUCTOR AND OTHER MALIBU DRIVERS.