AN ACR EMB-120 HAD A PARTIAL STALL DUE TO CLR ICING ON THE WINGS AND TAIL.

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ON THE NIGHT OF OCT/SUN/94 AT APPROX LATE PM XA15 LCL TIME; ON THE FLT BTWN SALT LAKE CITY AND ELKO; NEV; THE FO AND MYSELF ENCOUNTERED WHAT WE BELIEVE TO BE A TAIL ICE STALL SIT WHILE STARTING THE APCH INTO ELKO. IT STARTED APPROX 35 MI OUT OF BQU VOR. ZLC CLRED US TO 13000 FT AND WE STARTED TO DSND AT 180 KTS. WE COMPLETED THE DSCNT CHKLIST AND REVIEWED THE APCH FOR THE LDA; THEN NOTIFIED THE FLT ATTENDANT TO PREPARE THE CABIN FOR LNDG. WE LEVELED AT 13000 FT APPROX 10-15 MI E OF THE BQU VOR; AND WERE IN AND OUT OF THE TOPS (TOPS WERE ABOUT 13500 FT). WE STABILIZED THE AIRSPD AT 160 KTS IN PREPARATION FOR THE APCH. THE FO AND MYSELF BOTH CHKED FOR ICE ON THE LEADING EDGES OF THE WINGS AND SPINNER; BUT DID NOT SEE A SIGNIFICANT AMOUNT AT THAT TIME. THE CTR THEN CLRED US FOR THE LDA 23 APCH. WE CROSSED THE VOR AND I TURNED THE HDG BUG 035 DEGS AND SWITCHED OFF THE HALF-BANK ON THE FLT DIRECTOR. (I DID HAVE THE AUTOPLT ENGAGED WITH THE FLT DIRECTOR). IT WAS AT TIME SOMETHING WENT VERY WRONG. I GOT THE CLICKER AND STICK PUSHER ALMOST SIMULTANEOUSLY; THEN THE PLANE PITCHED OVER AND ROLLED STEEPLY TO THE R. AT THIS POINT MY HANDS WERE ALREADY ON THE CTL WHEEL. I DISCONNECTED THE AUTOPLT AND PUSHED THE PWR LEVERS UP; LEVELED THE WINGS AND PULLED THE NOSE BACK UP TO THE HORIZON. THE PLANE PITCHED OVER AND ROLLED TO THE R A SECOND TIME. I CALLED FOR MAX PWR (IF I DIDN'T ALREADY HAVE IT); LEVELED THE WINGS AND BROUGHT THE NOSE BACK UP TO THE HORIZON. WE THEN DECLARED AN EMER BECAUSE WE WERE NOT SURE EXACTLY WHAT THE PROB WAS; AND WANTED SUPPORT WHEN WE REACHED THE GND. I SERIOUSLY THOUGHT WE HAD LOST PART OF THE TAIL SECTION OR SOME OTHER PART OF THE ACFT. AT THE AIRSPD WE WERE INDICATING; THERE WAS NO REASON TO SUSPECT A STALL. WE RECOVERED CTL WHILE STILL IMC; AND HELD THE AIRSPD AT 190 KTS. THE FO GOT SOME GND CONTACT AND THEN THE ARPT. WE THEN BRIEFED THE PAX FOR AN EMER LNDG. WE NEVER SLOWED BELOW 190 KTS UNTIL SHORT FINAL. WE THEN SLOWED TO 160 KTS AND LANDED WITH NOPROBS. THE PAX RPTED NO INJURIES TO THE FLT ATTENDANT. SHE; AS WELL AS ALL PAX; WERE SECURED FOR LNDG. AFTER LNDG AND TAXIING TO THE RAMP; WE DEPLANED THE PAX AND INSPECTED THE ACFT FOR DAMAGE. WE OBSERVED CLR ICING ON THE LEADING EDGES OF THE WINGS AND SPINNER; AND WHAT APPEARED TO BE SIGNIFICANTLY MORE ICE ACCUMULATED ON THE HORIZ STABILIZER. I STRONGLY BELIEVE THIS EPISODE WAS THE RESULT OF ACCUMULATED ICE ON THE CRITICAL SURFACE OF THE TAIL. I BELIEVE THIS EPISODE COULD HAVE BEEN AVOIDED BY AN INCREASE IN AIRSPD OF 5-10 KTS. NEVER START A TURN AT LESS THAN 170 KTS WITHOUT FLAPS 15 DEGS IN RIGHT CONDITIONS WHEN CLR ICE IS PRESENT AND EVEN HARDER TO DETECT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID 'IT DEFINITELY SCARED THE S--- OUT OF ME!' WHEN DESCRIBING THIS INCIDENT; THE ACFT WAS AN EMB-120. THE ACFT HAS DEICING BOOTS ON THE LEADING EDGE OF THE WINGS AND TAIL. THESE WERE NOT ON; BUT EVERYTHING ELSE WAS ON. THE PROPELLERS ARE ELECTRICALLY ANTI-ICED; BUT THE SPINNER IS NOT ANTI-ICED OR DEICED. THE ACR PROC FOR WING AND TAIL DEICING IS TO WAIT UNTIL THERE IS 1/4 TO 1/2 INCH OF ICE BEFORE 'BREAKING THE BOOTS.' EARLIER APPLICATION OF THE BOOTS CAN JUST LIFT A THIN LAYER OF ICE UPON WHICH MORE ICE WILL FORM THAT CANNOT BE BROKEN OFF. THE ACR IS RE- EVALUATING ITS APCH PROCS; INCREASING THE AIRSPD TO 170 KTS AND 'BREAKING THE BOOTS' SOONER. THE EMB-120 IS CRITICAL IN CTR OF GRAVITY WHEN THE ACFT IS LOADED HEAVY IN THE TAIL. THE RPTR BELIEVES THAT THIS MAY HAVE BEEN THE CASE HERE; ALTHOUGH THE MANIFEST SHOWED ONLY 1000 LBS IN THE TAIL. THERE IS NO INDICATOR TO HELP THE FLC DETERMINE HOW THICK THE ICE IS ON THE WINGS; CLR ICE IS HARD TO DETECT AND MEASURE; ESPECIALLY AT NIGHT. SUPPLEMENTAL INFO FROM ACN 285730: THE CAPT STARTED A R TURN OUTBOUND. GOING THROUGH ABOUT 10-20 DEG BANK; WE SUDDENLY GOT THE STICK SHAKER; IMMEDIATELY FOLLOWED BY THE ACFT ROLLING HARD TO THE R AND PITCHING FORWARD. MY REACTION TO THIS WAS TO NOTE THE AIRSPD (APPROX 150 KTS) AND TO ASSIST THE CAPT IN ROLLING THE ACFT'S WINGS LEVEL. UPON POSTFLT INSPECTION OF THE ACFT; WE NOTED CLR ICE ON THE LOWER LEADING EDGES; CLR ICE ON THE SPINNERS AND QUITE A SUBSTANTIAL AMOUNT OF ICE ON THE HORIZ STABILIZER.