Narrative:

At the time of departure, the latest WX at pwk was reported as VFR. A PIREP solicited from an arriving aircraft reported 3000 ft ceiling. Upon departure, in-flight conditions deteriorated rapidly in snow to MVFR. As a precaution, I had an IFR flight plan on file, which I activated 3 mi west of pwk at 1900 ft MSL. I was cleared to climb and maintain 3000 ft on a southwest vector which took me towards dpa. I entered the base of the overcast at 2500 ft MSL. During the next 10 mins, I picked up 1/2 inch of rime ice. I decided to make a precautionary landing at dpa. The dpa ATIS was reporting 1100 ft ceilings. I informed the controller I was picking up ice and I needed to land at dpa. He gave me a vector for the ILS. While outbound on a parallel course to the ILS, the controller issued a 90 degree left turn through the final approach course for traffic. At this point I declared an emergency to prevent further delay. I continued to pick up ice, my airspeed decayed 25 KTS, and my altimeter and vsi's became unreliable. Pitot heat was on, and I informed controller of the problem. I was cleared to descend to 2500 ft MSL for a visual approach. I broke out at 2500 ft and landed without further incident. I used my handheld GPS to xchk altitude during descent. Automatic gear extension activated due to iced up probe. I decided not to override it.

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Original NASA ASRS Text

Title: PLT OF A PA28R ON AN IFR FLT EXPERIENCED ICING AND LOSS OF AIRSPD RESULTING IN DECLARING AN EMER AND DIVERTING TO LAND.

Narrative: AT THE TIME OF DEP, THE LATEST WX AT PWK WAS RPTED AS VFR. A PIREP SOLICITED FROM AN ARRIVING ACFT RPTED 3000 FT CEILING. UPON DEP, INFLT CONDITIONS DETERIORATED RAPIDLY IN SNOW TO MVFR. AS A PRECAUTION, I HAD AN IFR FLT PLAN ON FILE, WHICH I ACTIVATED 3 MI W OF PWK AT 1900 FT MSL. I WAS CLRED TO CLB AND MAINTAIN 3000 FT ON A SW VECTOR WHICH TOOK ME TOWARDS DPA. I ENTERED THE BASE OF THE OVCST AT 2500 FT MSL. DURING THE NEXT 10 MINS, I PICKED UP 1/2 INCH OF RIME ICE. I DECIDED TO MAKE A PRECAUTIONARY LNDG AT DPA. THE DPA ATIS WAS RPTING 1100 FT CEILINGS. I INFORMED THE CTLR I WAS PICKING UP ICE AND I NEEDED TO LAND AT DPA. HE GAVE ME A VECTOR FOR THE ILS. WHILE OUTBOUND ON A PARALLEL COURSE TO THE ILS, THE CTLR ISSUED A 90 DEG L TURN THROUGH THE FINAL APCH COURSE FOR TFC. AT THIS POINT I DECLARED AN EMER TO PREVENT FURTHER DELAY. I CONTINUED TO PICK UP ICE, MY AIRSPD DECAYED 25 KTS, AND MY ALTIMETER AND VSI'S BECAME UNRELIABLE. PITOT HEAT WAS ON, AND I INFORMED CTLR OF THE PROB. I WAS CLRED TO DSND TO 2500 FT MSL FOR A VISUAL APCH. I BROKE OUT AT 2500 FT AND LANDED WITHOUT FURTHER INCIDENT. I USED MY HANDHELD GPS TO XCHK ALT DURING DSCNT. AUTOMATIC GEAR EXTENSION ACTIVATED DUE TO ICED UP PROBE. I DECIDED NOT TO OVERRIDE IT.

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.