Narrative:

Upon picking up my aircraft after it received its annual inspection, I failed to check to see that the defroster vent was open for the windscreen. Since I never close it, I assumed that it would be open. After climbing from 1200 ft AGL to 4000 ft MSL in the clouds, my windscreen fogged up and I had difficulty to see anything forward of my position. At this point I knew it would be difficult to determine whether or not I was picking any ice up or not. I knew the tops of the clouds were probably less than 2000 ft above me, so I asked for higher and maneuvered my aircraft toward what looked to be a hole in the layer above. My poor forward visibility led me to fly into a cloud and pick up what looked to be light rime ice. I was only in the icing conditions for 15 seconds. Once I saw the ice, I immediately broke out on top and leveled out later on an 8000 ft MSL. I never put myself in danger, because I knew if I encountered any ice, that I would be able to get out of it at once. Once in level flight, I began to look around a bit more and saw that the defroster vent was closed. I then opened it up fully and the windscreen immediately cleared up. There was no ice left on the aircraft by this time. The rest of the flight was routine. I believe my failure to open the defroster could have led to a dangerous situation if there had been more icing in the clouds. There were 2 PIREPS of light ice 40 NM north of my position, but one was over 1 1/2 hours old. I knew there was forecasted ice above 4000 ft freezing level. Since there was not known ice along my route, I asked for and received a higher altitude, which I knew would put me above the clouds. If I had not been able to leave the icing conditions immediately, the foggy windscreen may have been a contributing factor to a dangerous situation. My judgement to assume its position as being open was an oversight on my part. I limited my ability to see forward and also my ability to determine if I was picking up any ice. I believe this report could benefit other higher time pilots. I believe myself to be a careful safety oriented pilot. However, on this occasion, I checked and doublechked everything -- or so I thought.

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Original NASA ASRS Text

Title: GA PLT ENTERED FORECAST AND RPTED ICING CONDITIONS WITH C172 NEAR SUW, WI.

Narrative: UPON PICKING UP MY ACFT AFTER IT RECEIVED ITS ANNUAL INSPECTION, I FAILED TO CHK TO SEE THAT THE DEFROSTER VENT WAS OPEN FOR THE WINDSCREEN. SINCE I NEVER CLOSE IT, I ASSUMED THAT IT WOULD BE OPEN. AFTER CLBING FROM 1200 FT AGL TO 4000 FT MSL IN THE CLOUDS, MY WINDSCREEN FOGGED UP AND I HAD DIFFICULTY TO SEE ANYTHING FORWARD OF MY POS. AT THIS POINT I KNEW IT WOULD BE DIFFICULT TO DETERMINE WHETHER OR NOT I WAS PICKING ANY ICE UP OR NOT. I KNEW THE TOPS OF THE CLOUDS WERE PROBABLY LESS THAN 2000 FT ABOVE ME, SO I ASKED FOR HIGHER AND MANEUVERED MY ACFT TOWARD WHAT LOOKED TO BE A HOLE IN THE LAYER ABOVE. MY POOR FORWARD VISIBILITY LED ME TO FLY INTO A CLOUD AND PICK UP WHAT LOOKED TO BE LIGHT RIME ICE. I WAS ONLY IN THE ICING CONDITIONS FOR 15 SECONDS. ONCE I SAW THE ICE, I IMMEDIATELY BROKE OUT ON TOP AND LEVELED OUT LATER ON AN 8000 FT MSL. I NEVER PUT MYSELF IN DANGER, BECAUSE I KNEW IF I ENCOUNTERED ANY ICE, THAT I WOULD BE ABLE TO GET OUT OF IT AT ONCE. ONCE IN LEVEL FLT, I BEGAN TO LOOK AROUND A BIT MORE AND SAW THAT THE DEFROSTER VENT WAS CLOSED. I THEN OPENED IT UP FULLY AND THE WINDSCREEN IMMEDIATELY CLRED UP. THERE WAS NO ICE LEFT ON THE ACFT BY THIS TIME. THE REST OF THE FLT WAS ROUTINE. I BELIEVE MY FAILURE TO OPEN THE DEFROSTER COULD HAVE LED TO A DANGEROUS SIT IF THERE HAD BEEN MORE ICING IN THE CLOUDS. THERE WERE 2 PIREPS OF LIGHT ICE 40 NM N OF MY POS, BUT ONE WAS OVER 1 1/2 HRS OLD. I KNEW THERE WAS FORECASTED ICE ABOVE 4000 FT FREEZING LEVEL. SINCE THERE WAS NOT KNOWN ICE ALONG MY RTE, I ASKED FOR AND RECEIVED A HIGHER ALT, WHICH I KNEW WOULD PUT ME ABOVE THE CLOUDS. IF I HAD NOT BEEN ABLE TO LEAVE THE ICING CONDITIONS IMMEDIATELY, THE FOGGY WINDSCREEN MAY HAVE BEEN A CONTRIBUTING FACTOR TO A DANGEROUS SIT. MY JUDGEMENT TO ASSUME ITS POS AS BEING OPEN WAS AN OVERSIGHT ON MY PART. I LIMITED MY ABILITY TO SEE FORWARD AND ALSO MY ABILITY TO DETERMINE IF I WAS PICKING UP ANY ICE. I BELIEVE THIS RPT COULD BENEFIT OTHER HIGHER TIME PLTS. I BELIEVE MYSELF TO BE A CAREFUL SAFETY ORIENTED PLT. HOWEVER, ON THIS OCCASION, I CHKED AND DOUBLECHKED EVERYTHING -- OR SO I THOUGHT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.