Narrative:

IFR flight from nqa to cnc. The preflight WX briefing included an airmet for possible icing in clouds in northern missouri and iowa, but ceilings were such that flight outside icing conditions was possible. The flight was unremarkable until jefferson, mo, where I encountered a thin overcast deck at about 5000-6000 ft MSL. At the time, I was in cruise flight at 4000 ft MSL with excellent visibility. Subsequently, I was cleared to proceed direct from the mcm VOR to the clariton NDB. I lowered my altitude to 3200 ft MSL to keep with the good visibility I had. By kirksville, mo, there was some light snow that reduced visibility to about 5 mi. I then flew over the town and airport of centerville, ia, with the beacon in sight. I then proceeded direct to the clariton NDB, and about 15 mi southeast I suddenly flew into the overcast layer. The dsm ATIS was broadcasting. I was unable to pick up the clariton AWOS, and didn't know the airport condition until dsm approach informed me of an 1100 ft ceiling with 3 mi in light snow. At the en route MEA of 3100 ft, I began picking up light mixed ice on the wings, and by the time I reached the NDB, enough ice had formed to cause me to feel uncomfortable shooting a non precision approach to a short runway with ice on the airframe. I then asked for vectors to dsm, and when informed that the long runway with an ILS was closed for snow removal, I declared an emergency to get that runway. I maintained a high speed over the fence and landed uneventfully. I feel my comfort level with the WX being better than forecast for much of the route led to a level of complacency that caused me to continue when I should've landed at centerville. The ice built so rapidly, I realized I needed help getting the aircraft on the ground. Flying an airplane with anti- and deicing equipment can lead to a false sense of security, even when flying a light unequipped aircraft, as in my case. Next time I will be much more attentive to WX conditions.

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Original NASA ASRS Text

Title: PLT OF AN SMA SEL ENCOUNTERED ICING CONDITIONS AND HAD TO DIVERT TO LAND AT A NEARBY LARGER ARPT, WITH AN ILS AND LONGER RWY.

Narrative: IFR FLT FROM NQA TO CNC. THE PREFLT WX BRIEFING INCLUDED AN AIRMET FOR POSSIBLE ICING IN CLOUDS IN NORTHERN MISSOURI AND IOWA, BUT CEILINGS WERE SUCH THAT FLT OUTSIDE ICING CONDITIONS WAS POSSIBLE. THE FLT WAS UNREMARKABLE UNTIL JEFFERSON, MO, WHERE I ENCOUNTERED A THIN OVCST DECK AT ABOUT 5000-6000 FT MSL. AT THE TIME, I WAS IN CRUISE FLT AT 4000 FT MSL WITH EXCELLENT VISIBILITY. SUBSEQUENTLY, I WAS CLRED TO PROCEED DIRECT FROM THE MCM VOR TO THE CLARITON NDB. I LOWERED MY ALT TO 3200 FT MSL TO KEEP WITH THE GOOD VISIBILITY I HAD. BY KIRKSVILLE, MO, THERE WAS SOME LIGHT SNOW THAT REDUCED VISIBILITY TO ABOUT 5 MI. I THEN FLEW OVER THE TOWN AND ARPT OF CENTERVILLE, IA, WITH THE BEACON IN SIGHT. I THEN PROCEEDED DIRECT TO THE CLARITON NDB, AND ABOUT 15 MI SE I SUDDENLY FLEW INTO THE OVCST LAYER. THE DSM ATIS WAS BROADCASTING. I WAS UNABLE TO PICK UP THE CLARITON AWOS, AND DIDN'T KNOW THE ARPT CONDITION UNTIL DSM APCH INFORMED ME OF AN 1100 FT CEILING WITH 3 MI IN LIGHT SNOW. AT THE ENRTE MEA OF 3100 FT, I BEGAN PICKING UP LIGHT MIXED ICE ON THE WINGS, AND BY THE TIME I REACHED THE NDB, ENOUGH ICE HAD FORMED TO CAUSE ME TO FEEL UNCOMFORTABLE SHOOTING A NON PRECISION APCH TO A SHORT RWY WITH ICE ON THE AIRFRAME. I THEN ASKED FOR VECTORS TO DSM, AND WHEN INFORMED THAT THE LONG RWY WITH AN ILS WAS CLOSED FOR SNOW REMOVAL, I DECLARED AN EMER TO GET THAT RWY. I MAINTAINED A HIGH SPD OVER THE FENCE AND LANDED UNEVENTFULLY. I FEEL MY COMFORT LEVEL WITH THE WX BEING BETTER THAN FORECAST FOR MUCH OF THE RTE LED TO A LEVEL OF COMPLACENCY THAT CAUSED ME TO CONTINUE WHEN I SHOULD'VE LANDED AT CENTERVILLE. THE ICE BUILT SO RAPIDLY, I REALIZED I NEEDED HELP GETTING THE ACFT ON THE GND. FLYING AN AIRPLANE WITH ANTI- AND DEICING EQUIP CAN LEAD TO A FALSE SENSE OF SECURITY, EVEN WHEN FLYING A LIGHT UNEQUIPPED ACFT, AS IN MY CASE. NEXT TIME I WILL BE MUCH MORE ATTENTIVE TO WX CONDITIONS.

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.