AN ATP; FLYING A C150 IN THE DARK IN ICING CONDITIONS; COMMITTED BOTH AN ALTDEV AND A HEADING DEV IN SDF'S AIRSPACE.

Narrative

I WAS FLYING SOLO IN CESSNA 150 FROM FORT WAYNE; IN (FWA) TO LOUISVILLE; KY (LOU) ON AN IFR FLT PLAN AT NIGHT. THE WX WAS FORECAST TO BE IMC ACROSS THE ENTIRE RTE WITH ICING POSSIBLE AT 6000 FT AND ABOVE; SO I FILED FOR 4000 FT. THE FIRST HALF OF THE FLT WAS UNEVENTFUL; BUT THEN I STARTED TO PICK UP LIGHT RIME ICE. I REQUESTED 3000 FT; HOPING THE TEMP WOULD BE WARM ENOUGH AT THAT ALT TO MELT THE ICE AND KEEP ADDITIONAL ICE FROM ACCUMULATING. I WAS STILL PICKING UP LIGHT RIME ICE AT 3000 FT SO I REQUESTED LOWER. THE CTR CTLR CLRED ME TO 2600 FT WHICH WAS THE LOWEST HE COULD ALLOW ME TO GO. I DIDN'T GET MUCH BETTER AT THAT ALT. THEN I WAS TOLD TO CHANGE TO LOUISVILLE APCH AND THAT THEY WANTED ME AT 3000 FT. I WAS UNABLE TO CLB TO 3000 FT AS MY AIRSPD HAD SLOWED TO ABOUT 65 KTS IN LEVEL FLT. IN ADDITION; LOUISVILLE APCH COULD NOT HEAR MY XMISSION EVEN THOUGH I COULD HEAR THEM CALLING ME. I DECIDED TO DIVERT TO MADISON; IN; AND TRY TO LAND THERE. I HAD NOT BEEN CLRED TO MADISON; BUT SINCE I WAS UNABLE TO CONTACT LOUISVILLE APCH TO MAKE THE REQUEST; I FELT IT WAS NECESSARY TO DIVERT GIVEN MY ICING SIT. THE DIVERSION TOOK ME ABOUT 5 MI OFF MY COURSE TO LOUISVILLE. WHEN I GOT OVER MADISON; MY AIRSPD HAD INCREASED ABOUT 5 KTS AND IT SEEMED AS THOUGH THE ICE WAS MELTING SOMEWHAT; SO I DECIDED TO CONTINUE TO LOUISVILLE. I WAS FINALLY ABLE TO CONTACT LOUISVILLE APCH; BUT WAS UNABLE TO CLB ABOVE 2600 FT. I FELT THAT MY FIRST; AND BIGGEST; ERROR WAS MAKING THE CHOICE TO FLY AT ALL THAT NIGHT. I JUSTIFIED MAKING THE FLT BECAUSE THE FORECAST CALLED FOR ICE AT ALTS HIGHER THAN I PLANNED TO FLY. I ALSO WANTED VERY MUCH TO GET HOME THAT NIGHT. HOWEVER; I SHOULD HAVE CONSIDERED THE CHANCE THAT ICING MIGHT ALSO AFFECT LOWER ALTS. SINCE THE AIRPLANE I WAS FLYING WAS NOT ICE PROTECTED I SHOULD NOT HAVE ATTEMPTED THE FLT. MY SECOND ERROR WAS NOT REQUESTING A LOWER ALT SOONER OR REQUESTING A TURN BACK TO AN ARPT WHERE I KNEW THAT ICING WASN'T A PROB. I WAITED TOO LONG AND ACCUMULATED TOO MUCH ICE BEFORE I FINALLY MADE ANY REQUESTS.