Narrative:

The aircraft suddenly accumulated a load of clear ice. Airspeed was decreasing, with trim change, and power was increased from 65% lean to 75% best power. After the addition of power air speed moved into the yellow caution zone. The pitot heater circuit breaker was checked and found in. The rate of climb went to plus 1000 ft/min--altimeter was solid at 4000 ft. At the time identification did not realize that ice was rapidly forming on the aircraft. I was aware of small amounts of rime ice on the leading edge of the wing. Within 15 seconds of the above I declared an emergency with minneapolis departure and asked for vectors back to flying cloud airport, point of departure. Vectors were immediately given with a block altitude assignment from 4000 to 2500 ft. I was extremely cautious executing the 180 degree turn and probably a bit tense on the rudder and had to stop the turn to see if the directional gyro was following. The pitot static system returned to normal with the aircraft in a 300 ft/min descent passing 3,200 ft still IMC. At 2500 ft 2 mi north of flying cloud airport VMC were entered and a landing was made in quite windy conditions. At the time I was still not aware of the amount of ice on the aircraft. I did note that a lot of power was required on final but figured this was normal cause of the head wind. Inspection of the aircraft after parking revealed a one-eighth inch sheet of ice on the bottom of the wing from the tip to about 1 and one-half ft from the wing roots. No ice was found on the top of the wing or on the fuselage. The ice was hard to see until it started to cracking melting. The pitot tube was checked and was warm. In the above case ATC's actions greatly reduced my workload during a period when I had to concentrate on flying the aircraft with a partial instrument failure in turbulent IMC. Controllers actions significantly contributed to my safety. I hope somehow the controllers and their supervisors learn how much I appreciate their help.

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Original NASA ASRS Text

Title: SMA ENCOUNTERED ICING, DECLARED EMERGENCY AND WAS VECTORED BACK TO ARPT.

Narrative: THE ACFT SUDDENLY ACCUMULATED A LOAD OF CLEAR ICE. AIRSPEED WAS DECREASING, WITH TRIM CHANGE, AND POWER WAS INCREASED FROM 65% LEAN TO 75% BEST POWER. AFTER THE ADDITION OF POWER AIR SPEED MOVED INTO THE YELLOW CAUTION ZONE. THE PITOT HEATER CIRCUIT BREAKER WAS CHECKED AND FOUND IN. THE RATE OF CLIMB WENT TO PLUS 1000 FT/MIN--ALTIMETER WAS SOLID AT 4000 FT. AT THE TIME ID DID NOT REALIZE THAT ICE WAS RAPIDLY FORMING ON THE ACFT. I WAS AWARE OF SMALL AMOUNTS OF RIME ICE ON THE LEADING EDGE OF THE WING. WITHIN 15 SECONDS OF THE ABOVE I DECLARED AN EMER WITH MINNEAPOLIS DEPARTURE AND ASKED FOR VECTORS BACK TO FLYING CLOUD AIRPORT, POINT OF DEPARTURE. VECTORS WERE IMMEDIATELY GIVEN WITH A BLOCK ALTITUDE ASSIGNMENT FROM 4000 TO 2500 FT. I WAS EXTREMELY CAUTIOUS EXECUTING THE 180 DEG TURN AND PROBABLY A BIT TENSE ON THE RUDDER AND HAD TO STOP THE TURN TO SEE IF THE DIRECTIONAL GYRO WAS FOLLOWING. THE PITOT STATIC SYSTEM RETURNED TO NORMAL WITH THE ACFT IN A 300 FT/MIN DESCENT PASSING 3,200 FT STILL IMC. AT 2500 FT 2 MI NORTH OF FLYING CLOUD AIRPORT VMC WERE ENTERED AND A LANDING WAS MADE IN QUITE WINDY CONDITIONS. AT THE TIME I WAS STILL NOT AWARE OF THE AMOUNT OF ICE ON THE ACFT. I DID NOTE THAT A LOT OF POWER WAS REQUIRED ON FINAL BUT FIGURED THIS WAS NORMAL CAUSE OF THE HEAD WIND. INSPECTION OF THE ACFT AFTER PARKING REVEALED A ONE-EIGHTH INCH SHEET OF ICE ON THE BOTTOM OF THE WING FROM THE TIP TO ABOUT 1 AND ONE-HALF FT FROM THE WING ROOTS. NO ICE WAS FOUND ON THE TOP OF THE WING OR ON THE FUSELAGE. THE ICE WAS HARD TO SEE UNTIL IT STARTED TO CRACKING MELTING. THE PITOT TUBE WAS CHECKED AND WAS WARM. IN THE ABOVE CASE ATC'S ACTIONS GREATLY REDUCED MY WORKLOAD DURING A PERIOD WHEN I HAD TO CONCENTRATE ON FLYING THE ACFT WITH A PARTIAL INSTRUMENT FAILURE IN TURBULENT IMC. CTLRS ACTIONS SIGNIFICANTLY CONTRIBUTED TO MY SAFETY. I HOPE SOMEHOW THE CTLRS AND THEIR SUPERVISORS LEARN HOW MUCH I APPRECIATE THEIR HELP.

Data retrieved from NASA's ASRS site as of August 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.