SMA DSNDS INTO KNOWN ICING CONDITIONS.

Narrative

I WAS FLYING AN ANGEL FLT MEDICAL TRANSPORTATION MISSION INVOLVING FLT FROM OAK TO ACV TO PICK UP AN 18-MONTH OLD CANCER PATIENT AND HIS PARENTS AND TRANSPORT THEM TO OAKLAND. ON THE WAY UP; AT 10000 FT NEAR MENDOCINO VOR (ENI); I PICKED UP A TRACE OF RIME ICE. I REQUESTED 12000 FT AND RECEIVED IT; THEREBY REMAINING ABOVE THE CLOUD DECK. APCHING ACV I HEARD 2 RPTS BY PLTS OF ACCUMULATING 1/4 INCH OF LIGHT RIME ICE ON THE DSCNT INTO ACV. THEY WERE ON THE ILS RWY 32 (CIRCLE-TO-LAND RWY 14) APCH. ZSE ADVISED ME OF THE RPTED ICING. HAVING RECEIVED THE SURFACE CONDITIONS AT ACV TEMP 46 DEGS; DEWPOINT 42; WIND 110 DEGS AT 10 KTS; VISIBILITY 10 MI); I WAS CONFIDENT THAT WHATEVER ICING I PICKED UP ON THE APCH WOULD MELT OFF WHEN I GOT DOWN TO 5500 FT OR SO. I THUS CONTINUED THE FLT AS PLANNED. INDEED; ON THE DSCNT I EXPERIENCED THE SAME ICING AS RPTED BY EARLIER PLTS. IT MELTED OFF AT 5000-6000 FT AND I LANDED SAFELY. FOR THE RETURN FLT; WITH PAX; I CHOSE TO WAIT UNTIL THE FRONT PASSED SOMEWHAT; CLBED ON THE HOCUT DEP TO 11000 FT IN VFR CONDITIONS AND RETURNED WITHOUT INCIDENT TO OAKLAND. I AM FILING THIS BECAUSE I VIOLATED THE LIMITS OF MY ACFT WHICH IS NOT CERTIFIED FOR FLT INTO KNOWN ICING CONDITIONS. BUT GIVEN THE WX BELOW THE CLOUDS (WELL ABOVE FREEZING) AND THE RELATIVE IMPORTANCE OF THE MISSION; I FEEL I ACTED RESPONSIBLY. HAD THE GND TEMP BEEN CLOSER TO FREEZING; OR THE CEILING (4500 FT) BEEN LOWER; I WOULD NOT HAVE DSNDED FOR THIS APCH.