A PART 135 CARGO PLT DSNDED BELOW THE MDA WHILE ON AN IAP TO AVOID CONTINUED FLT IN ICING CONDITIONS. THE SURFACE OBSERVATION RPTS WERE FOR LIGHT FREEZING DRIZZLE; AND THE PLT HAD ENCOUNTERED MODERATE TO SEVERE ICING CONDITIONS ENRTE; AND AT THE DEST.

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FAR 135 FREIGHT OPS DEPARTED MEM DIRECT TO ASG; AR. INITIALLY I LEVELED AT 6000 FT AND STARTED PICKING UP MODERATE TO SEVERE ICE. CLBED TO 9000 FT AND FINALLY LEVELED AT 10000 FT. AT 10000 FT WAS IN BTWN LAYERS AND STOPPED PICKING UP ICE. AS I CONTINUED TOWARDS SPRINGDALE; PROBABLY 60-70 MI E; I AGAIN PICKED UP LIGHT TO MODERATE ICE SO I REQUESTED 6000 FT AND DSNDED TO TRY TO FIND AN INVERSION. MY ACFT HAS FULL DEICE EQUIP AND WAS WORKING UP TO THIS POINT. NO INVERSION WAS FOUND AND SO I CLBED BACK TO 10000 FT. ONCE AT 10000 FT I WAS IN THE CLR AND ICE ACCUMULATION WAS NIL. I DECIDED TO STAY AT 10000 FT FOR THE DURATION OF THE FLT. AFTER BEING HANDED OFF TO RAZORBACK APCH; I TOLD THE CTLR THAT I WANTED TO STAY AT 10000 FT UNTIL JUST 15 MI OUTSIDE THE IAF. I DSNDED FROM 10000 FT TO 4500 FT AND FINALLY TO 3000 FT ONCE ESTABLISHED ON THE APCH. DUE TO MY LACK OF EXPERIENCE I WAS NOT READY FOR WHAT HAPPENED. DSNDING; I FLEW INTO FREEZING DRIZZLE AND PICKED UP SUCH A LOAD OF ICE THAT I HAD CLOSE TO FULL PWR WHEN I LEVELED AT THE MDA. STILL PICKING UP ICE; I COULD SEE THE GND VERTLY OUT THE SIDE WINDOW AND FELT I WAS IN AN EMER SIT AND DSNDED BELOW THE MDA UNTIL I BROKE OUT AND SAW THE RWY AT WHICH POINT I MADE A NORMAL APCH AND LNDG. THE POSSIBILITY OF MISSING THE APCH SAFELY; I FELT; WAS CLOSE TO IMPOSSIBLE WITH THE LOAD OF ICE THAT I HAD PICKED UP. THEREFORE; MY ONLY OPTION WAS TO DSND BELOW THE MDA. 'WX WAS' FYV MEASURED 800 FT OVCST; 1 1/2 MI VISIBILITY IN LIGHT FREEZING DRIZZLE; LIGHT SNOW PELLETS AND FOG. ROG WAS 1400 FT OVCST; 10 MI VISIBILITY AND WINDS WERE FROM 020 DEGS AT 13 KTS; GUSTING TO 17 KTS.