Narrative:

While on the eau claire 4 arrival the approach controller informed us that numerous aircraft were reporting moderate icing on approach into msp. We were 20 NM west of eau on the 281 degree radial at 9000 ft MSL in VMC with the tops below us at approximately 8000 ft MSL. We were then assigned 8000 ft and given a vector to the west off the arrival. We started to pick up moderate rime icing and the controller turned us back toward msp. The deice boots were on continuously, propeller heat on normal and engine ice on. The temperature was -7 degrees C at 8000 ft when we first encountered the icing and fluctuated between -10 degrees and -4 degrees throughout the descent. The ATIS was reporting northwest winds about 10 KTS, 800 ft overcast, light freezing rain, mist and snow. The boot cycle was too slow so I was manually activating the boots with one cycle to keep up with the building ice. The ice would clear after each cycle. The icing was in narrow areas. The wings would acquire ice quickly for a few mins then we wouldn't pick up any. Then we would fly into another area where it would ice up quickly again. I informed ATC that we were definitely getting moderate (ice) and would like lower. She cleared us to 4000 ft at our discretion and we started a slow descent at 500 FPM. At rated cruise power we were only indicating 200 KTS with large ice formations on the wipers and the entire spinner was covered. The side windows were developing ice in the forward 4 inches. These were vertical ridges running parallel to the window support frame spaced approximately .5 inches apart. First officer had turned the autoplt off with the first encounter and reported no flight control problems. As we continued down below 7000 ft the ice became severe. The oil cooler duct was completely blocked, the spinner was covered with large accumulations to the blades, the face of the engine was covered and the wing unprotected areas had large formations. The wipers had accumulated a 2-3 inch diameter of ice on them. The ice was accumulating as fast as I could activate the boots. I turned the propeller heat to maximum due to the severe nature of the ice. ATC asked us to slow to 170 KTS but we responded 'unable due to severe ice' and asked how long the final was. ATC told us to expect a 30 NM final, we then told them that we were in severe ice and would take either runway and that we needed to get down soon. The aircraft still had no control problems and we set up for the approach. We were 28000 pounds, which gave us vref speeds of 120 KTS/132 KTS. We decided to use a vref of 130 KTS due to the ice. We discussed the extension of the flaps and the possibility of a tailplane stall and that we would fly no slower than 140 KTS on approach. If we extended flaps and encountered any strange control problems we would retract the flaps and continue with a no flap landing. ATC vectored us on to the localizer of runway 30R about 10 NM outside the FAF. Again they asked us to slow and we refused and told them it was all we could do to maintain 180 KTS in level flight. We extended the flaps 7 degrees to see if any control problem existed with flaps out, then selected 15 degrees. We continued at 160 KTS and agreed that we would hold that speed to the threshold. They handed us off to tower just before the FAF and we were now getting moderate ice but I still was activating the boots manually about every min to about 1 NM final. Tower cleared us to land and asked us to slow again. We told them that we would be flying 160 KTS all the way to the runway. We completed the final check with flaps 20 degrees and still no problem. We encountered the freezing rain about 2000 ft AGL and began getting severe ice again. I activated the boots one last time before landing. First officer began slowing to 140 KTS as we crossed the threshold and landed normally. I inspected the aircraft after all the passenger deplaned. I found ice behind the boots on the underside of the wings extending about 2 ft back and the top about 8 inches back. The nose was completely covered with about 2-3 inches on the radome and thinning out as it spread aft. The flap actuator fairing had accumulations and the lower communication antennae had a 1 inch ice ridge the entire length.the tail vortex generators all had accumulations. The oil cooler was blocked and the wings unprotected surfaces had large flat accumulations.

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Original NASA ASRS Text

Title: ACR FLT ENCOUNTERS SEVERE ICING IN DSCNT AND APCH TO MSP.

Narrative: WHILE ON THE EAU CLAIRE 4 ARR THE APCH CTLR INFORMED US THAT NUMEROUS ACFT WERE RPTING MODERATE ICING ON APCH INTO MSP. WE WERE 20 NM W OF EAU ON THE 281 DEG RADIAL AT 9000 FT MSL IN VMC WITH THE TOPS BELOW US AT APPROX 8000 FT MSL. WE WERE THEN ASSIGNED 8000 FT AND GIVEN A VECTOR TO THE W OFF THE ARR. WE STARTED TO PICK UP MODERATE RIME ICING AND THE CTLR TURNED US BACK TOWARD MSP. THE DEICE BOOTS WERE ON CONTINUOUSLY, PROP HEAT ON NORMAL AND ENG ICE ON. THE TEMP WAS -7 DEGS C AT 8000 FT WHEN WE FIRST ENCOUNTERED THE ICING AND FLUCTUATED BTWN -10 DEGS AND -4 DEGS THROUGHOUT THE DSCNT. THE ATIS WAS RPTING NW WINDS ABOUT 10 KTS, 800 FT OVCST, LIGHT FREEZING RAIN, MIST AND SNOW. THE BOOT CYCLE WAS TOO SLOW SO I WAS MANUALLY ACTIVATING THE BOOTS WITH ONE CYCLE TO KEEP UP WITH THE BUILDING ICE. THE ICE WOULD CLR AFTER EACH CYCLE. THE ICING WAS IN NARROW AREAS. THE WINGS WOULD ACQUIRE ICE QUICKLY FOR A FEW MINS THEN WE WOULDN'T PICK UP ANY. THEN WE WOULD FLY INTO ANOTHER AREA WHERE IT WOULD ICE UP QUICKLY AGAIN. I INFORMED ATC THAT WE WERE DEFINITELY GETTING MODERATE (ICE) AND WOULD LIKE LOWER. SHE CLRED US TO 4000 FT AT OUR DISCRETION AND WE STARTED A SLOW DSCNT AT 500 FPM. AT RATED CRUISE PWR WE WERE ONLY INDICATING 200 KTS WITH LARGE ICE FORMATIONS ON THE WIPERS AND THE ENTIRE SPINNER WAS COVERED. THE SIDE WINDOWS WERE DEVELOPING ICE IN THE FORWARD 4 INCHES. THESE WERE VERT RIDGES RUNNING PARALLEL TO THE WINDOW SUPPORT FRAME SPACED APPROX .5 INCHES APART. FO HAD TURNED THE AUTOPLT OFF WITH THE FIRST ENCOUNTER AND RPTED NO FLT CTL PROBS. AS WE CONTINUED DOWN BELOW 7000 FT THE ICE BECAME SEVERE. THE OIL COOLER DUCT WAS COMPLETELY BLOCKED, THE SPINNER WAS COVERED WITH LARGE ACCUMULATIONS TO THE BLADES, THE FACE OF THE ENG WAS COVERED AND THE WING UNPROTECTED AREAS HAD LARGE FORMATIONS. THE WIPERS HAD ACCUMULATED A 2-3 INCH DIAMETER OF ICE ON THEM. THE ICE WAS ACCUMULATING AS FAST AS I COULD ACTIVATE THE BOOTS. I TURNED THE PROP HEAT TO MAX DUE TO THE SEVERE NATURE OF THE ICE. ATC ASKED US TO SLOW TO 170 KTS BUT WE RESPONDED 'UNABLE DUE TO SEVERE ICE' AND ASKED HOW LONG THE FINAL WAS. ATC TOLD US TO EXPECT A 30 NM FINAL, WE THEN TOLD THEM THAT WE WERE IN SEVERE ICE AND WOULD TAKE EITHER RWY AND THAT WE NEEDED TO GET DOWN SOON. THE ACFT STILL HAD NO CTL PROBS AND WE SET UP FOR THE APCH. WE WERE 28000 LBS, WHICH GAVE US VREF SPDS OF 120 KTS/132 KTS. WE DECIDED TO USE A VREF OF 130 KTS DUE TO THE ICE. WE DISCUSSED THE EXTENSION OF THE FLAPS AND THE POSSIBILITY OF A TAILPLANE STALL AND THAT WE WOULD FLY NO SLOWER THAN 140 KTS ON APCH. IF WE EXTENDED FLAPS AND ENCOUNTERED ANY STRANGE CTL PROBS WE WOULD RETRACT THE FLAPS AND CONTINUE WITH A NO FLAP LNDG. ATC VECTORED US ON TO THE LOC OF RWY 30R ABOUT 10 NM OUTSIDE THE FAF. AGAIN THEY ASKED US TO SLOW AND WE REFUSED AND TOLD THEM IT WAS ALL WE COULD DO TO MAINTAIN 180 KTS IN LEVEL FLT. WE EXTENDED THE FLAPS 7 DEGS TO SEE IF ANY CTL PROB EXISTED WITH FLAPS OUT, THEN SELECTED 15 DEGS. WE CONTINUED AT 160 KTS AND AGREED THAT WE WOULD HOLD THAT SPD TO THE THRESHOLD. THEY HANDED US OFF TO TWR JUST BEFORE THE FAF AND WE WERE NOW GETTING MODERATE ICE BUT I STILL WAS ACTIVATING THE BOOTS MANUALLY ABOUT EVERY MIN TO ABOUT 1 NM FINAL. TWR CLRED US TO LAND AND ASKED US TO SLOW AGAIN. WE TOLD THEM THAT WE WOULD BE FLYING 160 KTS ALL THE WAY TO THE RWY. WE COMPLETED THE FINAL CHK WITH FLAPS 20 DEGS AND STILL NO PROB. WE ENCOUNTERED THE FREEZING RAIN ABOUT 2000 FT AGL AND BEGAN GETTING SEVERE ICE AGAIN. I ACTIVATED THE BOOTS ONE LAST TIME BEFORE LNDG. FO BEGAN SLOWING TO 140 KTS AS WE CROSSED THE THRESHOLD AND LANDED NORMALLY. I INSPECTED THE ACFT AFTER ALL THE PAX DEPLANED. I FOUND ICE BEHIND THE BOOTS ON THE UNDERSIDE OF THE WINGS EXTENDING ABOUT 2 FT BACK AND THE TOP ABOUT 8 INCHES BACK. THE NOSE WAS COMPLETELY COVERED WITH ABOUT 2-3 INCHES ON THE RADOME AND THINNING OUT AS IT SPREAD AFT. THE FLAP ACTUATOR FAIRING HAD ACCUMULATIONS AND THE LOWER COM ANTENNAE HAD A 1 INCH ICE RIDGE THE ENTIRE LENGTH.THE TAIL VORTEX GENERATORS ALL HAD ACCUMULATIONS. THE OIL COOLER WAS BLOCKED AND THE WINGS UNPROTECTED SURFACES HAD LARGE FLAT ACCUMULATIONS.

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.