PLT OF A PIPER CHEROKEE ENTERED ICING CONDITIONS DURING TRANSITION FOR AN ILS APCH CAUSING RPTR TO ABANDON APCH AND REQUEST A HIGHER ALT. HE BECAME DISTR BY THE ACFT ICING; AND LOSS OF CLB PERFORMANCE; AND OVERSHOT ASSIGNED ALT.

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I WAS BEING VECTORED TO INTERCEPT THE LOC OUTSIDE THE OUTER ON APCH TO RWY 20L ILS PDK. CLOUD TOPS AT 4000 FT MSL. DURING DSCNT TO 3000 FT FROM 4000 FT; ACFT BEGAN TO PICK UP RIME AT OR ABOUT 3300 FT MSL. WITH NO ICE EQUIP ON BOARD; I ASKED TO ABANDON APCH AND WAS CLRED TO DO SO AND CLRED BACK TO 4000 FT. UPON REACHING 4000 FT; ACFT WAS STILL IN IMC AND STILL PICKING UP ICE. DISTR BY THE ICE; I CLBED TO 4400 FT BEFORE RECEIVING ANOTHER CLRNC TO 5000 FT. I ENCOUNTERED VISUAL CONDITIONS ABOUT 4800 FT AND ICE SUBLIMATED THERE. DURING THE CLB; ACFT WAS ONLY GETTING +/-300 FPM CLB AND I WAS UNABLE TO COMPLY WITH ATC HDG OF 340 DEGS UNTIL VMC. I BELIEVE THE ACFT HAD COLLECTED AS MUCH AS 1 INCH OF RIME ALONG ALL LEADING EDGES AND THE WINDSHIELD WAS ICED FROM THE DASH UP TO THE VISORS AS WELL. ATC INFORMED THAT NO OTHERS HAD RPTED THIS CONDITION ON THIS DAY. I BELIEVE I MADE A GOOD JUDGEMENT CALL WHEN I ABANDONED THE APCH; AS I WAS ALREADY AT MEA AND STILL 3 MI FROM THE NEXT STEPDOWN FIX. I BROKE THE ALT ASSIGNMENT BECAUSE I WAS DISTR BY THE SEVERITY OF THE SIT. I WAS UNABLE TO COMPLY WITH THE 340 DEG HDG ASSIGNMENT DUE TO DECREASED LIFT ENCOUNTERED DURING THE TURN AND A REAL DESIRE TO RETURN TO VMC ASAP. TEMP AT PDK WAS 4 DEGS C; AND I AM TROUBLED THAT RPTEDLY NO OTHERS HAD ENCOUNTERED ICE WHILE ON DSCNT. I AM SURE PDK HAD AT LEAST 100 LNDGS PRIOR TO MINE THAT DAY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT HE WAS VERY WORRIED WHEN FINDING HIMSELF IN THIS SIT SINCE THE ICE BUILT UP SO QUICKLY. SINCE HE HAD LIMITED INST FLYING EXPERIENCE; MOSTLY IN VMC TRAINING ENVIRONMENT; HE REACTED TO WHAT HE HAD BEEN TAUGHT; WHICH WAS TO CLB OUT OF THE ICE SINCE HE KNEW HE WOULD BE IN THE CLOUDS FOR SEVERAL MI. HE STATED THAT HE HAD LEARNED A LOT FROM THIS EXPERIENCE AND WILL BE VERY RESPECTFUL OF POSSIBLE ICING IN THE FUTURE. HE NOTED THAT THERE WAS ANOTHER PLT SHORTLY AFTER HE HAD CLBED ABOVE THE OVCST THAT ALSO RPTED ICE AND THAT MOST OF THE OTHER PLTS WERE SEVERAL MI S OF HIS LOCATION SINCE THEY HAD DME AND COULD MAKE A STRAIGHT-IN APCH WITHOUT THE NEED TO CIRCLE TO LAND; HAD NOT EXPERIENCED ANY ICE.