Narrative:

I was transporting the aircraft to miv for routine maintenance. I took off from iny and climbed to 2000 ft for the short (16 mi) flight. Temperature on the ground was 45 degrees F, ceiling was about 5000 ft MSL and visibility was unrestr. Upon reaching cruise altitude, I was able to see miv. The WX appeared to be clear. Upon reaching 1/2 way to miv, I noticed clear ice forming on the windshield. There was no apparent visible moisture. I must have flown into an area of mild freezing drizzle that was invisible to the eye. The temperature was approximately 32 degrees F, and I was in the clear, but the ice continued to form. I was surprised, but decided to descend into warmer air and began to set up to land. I estimated about 1/4 inch of clear ice formed on the windshield and leading edges of the wings. At 500 ft, no further ice formed, but it didn't melt off either. The defroster cleared a small area of the windshield so I was able to see. Rather than maneuver the iced up airframe, I decided to make a higher power straight-in approach at miv, without flaps. The ice began to melt off on short final (about 300 ft). I landed without incident. I was surprised that I accumulated ice without any apparent visible moisture, in good VMC. I previously didn't think this was possible. All pilots should be aware of this potentially serious icing threat.

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Original NASA ASRS Text

Title: A C172 PVT PLT ENCOUNTERS CLR ICING ON THE WINGS AND WINDSHIELD WHILE IN VMC AT 2000 FT MSL 10 MI E OF MIV, NJ.

Narrative: I WAS TRANSPORTING THE ACFT TO MIV FOR ROUTINE MAINT. I TOOK OFF FROM INY AND CLBED TO 2000 FT FOR THE SHORT (16 MI) FLT. TEMP ON THE GND WAS 45 DEGS F, CEILING WAS ABOUT 5000 FT MSL AND VISIBILITY WAS UNRESTR. UPON REACHING CRUISE ALT, I WAS ABLE TO SEE MIV. THE WX APPEARED TO BE CLR. UPON REACHING 1/2 WAY TO MIV, I NOTICED CLR ICE FORMING ON THE WINDSHIELD. THERE WAS NO APPARENT VISIBLE MOISTURE. I MUST HAVE FLOWN INTO AN AREA OF MILD FREEZING DRIZZLE THAT WAS INVISIBLE TO THE EYE. THE TEMP WAS APPROX 32 DEGS F, AND I WAS IN THE CLR, BUT THE ICE CONTINUED TO FORM. I WAS SURPRISED, BUT DECIDED TO DSND INTO WARMER AIR AND BEGAN TO SET UP TO LAND. I ESTIMATED ABOUT 1/4 INCH OF CLR ICE FORMED ON THE WINDSHIELD AND LEADING EDGES OF THE WINGS. AT 500 FT, NO FURTHER ICE FORMED, BUT IT DIDN'T MELT OFF EITHER. THE DEFROSTER CLRED A SMALL AREA OF THE WINDSHIELD SO I WAS ABLE TO SEE. RATHER THAN MANEUVER THE ICED UP AIRFRAME, I DECIDED TO MAKE A HIGHER PWR STRAIGHT-IN APCH AT MIV, WITHOUT FLAPS. THE ICE BEGAN TO MELT OFF ON SHORT FINAL (ABOUT 300 FT). I LANDED WITHOUT INCIDENT. I WAS SURPRISED THAT I ACCUMULATED ICE WITHOUT ANY APPARENT VISIBLE MOISTURE, IN GOOD VMC. I PREVIOUSLY DIDN'T THINK THIS WAS POSSIBLE. ALL PLTS SHOULD BE AWARE OF THIS POTENTIALLY SERIOUS ICING THREAT.

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.