Narrative:

Normal preflight WX briefing, mid-morning, no PIREPS. At 4000' MSL I encountered icing conditions that had not been forecast for that area, moderate rime and mixed. I asked cle approach for 3000'. At that time they were unable. OAT was right at 30 degrees F. Within 20 mins I had 1 1/2-2' of ice on the aircraft. I then demanded 3000' MSL. The controller asked if I was icing and I confirmed yes. He then cleared me for 3000'. After reaching 3000' temperature was 34 degrees F. I didn't lose the ice. I was unable to maintain 3000' and drifted down 300' to 2700'. I then requested minimum en route hoping to lose the ice. The controller then assigned me 2600' or 2500', I'm not sure. In any case I couldn't maintain it. He informed me that my ground speed was down to 60 KTS. I had 70 KTS indicated. He asked if I would like vectors to the nearest airport and named the airport. I replied negative, that an NDB approach wouldn't work. I continued on knowing that I only had approximately 16 NM to go. The ice had not yet left the aircraft. For a short period I was able to maintain my assigned altitude of 2500'. Then light turbulence caused me to drift down to 2250'. Now, 6 mi from the OM, the controller informed me of approach instructions and that he would vector me inside the marker. Due to ice on the aircraft antenna, radio accuracy was marginal. WX now 300' overcast, 1 mi in fog, temperature 36 degrees F, dew point 34. Either between the vectors or radio localizer reception I was too close to the airport for an approach. Assigned 050 degree heading for racetrack for another approach. Intercepted localizer with a positive signal and started down the slope. Contacted tower. Made decision of only 10 degree flap when airport was in sight. Was cleared to land and did so. Main concerns: altitudes; also oil temperatures were extremely high almost critical. Carburetor heat was applied every 2-3 mins. From the second request for 3000' full power had been maintained clear to T/D.

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Original NASA ASRS Text

Title: SMA PICKS UP UNFORECAST ICE AND IS UNABLE TO MAINTAIN ALT WITH FULL THROTTLE.

Narrative: NORMAL PREFLT WX BRIEFING, MID-MORNING, NO PIREPS. AT 4000' MSL I ENCOUNTERED ICING CONDITIONS THAT HAD NOT BEEN FORECAST FOR THAT AREA, MODERATE RIME AND MIXED. I ASKED CLE APCH FOR 3000'. AT THAT TIME THEY WERE UNABLE. OAT WAS RIGHT AT 30 DEGS F. WITHIN 20 MINS I HAD 1 1/2-2' OF ICE ON THE ACFT. I THEN DEMANDED 3000' MSL. THE CTLR ASKED IF I WAS ICING AND I CONFIRMED YES. HE THEN CLRED ME FOR 3000'. AFTER REACHING 3000' TEMP WAS 34 DEGS F. I DIDN'T LOSE THE ICE. I WAS UNABLE TO MAINTAIN 3000' AND DRIFTED DOWN 300' TO 2700'. I THEN REQUESTED MINIMUM ENRTE HOPING TO LOSE THE ICE. THE CTLR THEN ASSIGNED ME 2600' OR 2500', I'M NOT SURE. IN ANY CASE I COULDN'T MAINTAIN IT. HE INFORMED ME THAT MY GND SPD WAS DOWN TO 60 KTS. I HAD 70 KTS INDICATED. HE ASKED IF I WOULD LIKE VECTORS TO THE NEAREST ARPT AND NAMED THE ARPT. I REPLIED NEGATIVE, THAT AN NDB APCH WOULDN'T WORK. I CONTINUED ON KNOWING THAT I ONLY HAD APPROX 16 NM TO GO. THE ICE HAD NOT YET LEFT THE ACFT. FOR A SHORT PERIOD I WAS ABLE TO MAINTAIN MY ASSIGNED ALT OF 2500'. THEN LIGHT TURB CAUSED ME TO DRIFT DOWN TO 2250'. NOW, 6 MI FROM THE OM, THE CTLR INFORMED ME OF APCH INSTRUCTIONS AND THAT HE WOULD VECTOR ME INSIDE THE MARKER. DUE TO ICE ON THE ACFT ANTENNA, RADIO ACCURACY WAS MARGINAL. WX NOW 300' OVCST, 1 MI IN FOG, TEMP 36 DEGS F, DEW POINT 34. EITHER BTWN THE VECTORS OR RADIO LOC RECEPTION I WAS TOO CLOSE TO THE ARPT FOR AN APCH. ASSIGNED 050 DEG HDG FOR RACETRACK FOR ANOTHER APCH. INTERCEPTED LOC WITH A POSITIVE SIGNAL AND STARTED DOWN THE SLOPE. CONTACTED TWR. MADE DECISION OF ONLY 10 DEG FLAP WHEN ARPT WAS IN SIGHT. WAS CLRED TO LAND AND DID SO. MAIN CONCERNS: ALTS; ALSO OIL TEMPS WERE EXTREMELY HIGH ALMOST CRITICAL. CARB HEAT WAS APPLIED EVERY 2-3 MINS. FROM THE SECOND REQUEST FOR 3000' FULL PWR HAD BEEN MAINTAINED CLEAR TO T/D.

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.