EMB120 ACFT IN HOLDING PATTERN ENCOUNTERED INTERMITTENT ICING WHICH RESULTED IN AN ACFT UPSET. ACFT DISPLAYED APCH TO STALL CHARACTERISTICS WHEN ENTERING STANDARD RATE TURN IN HOLDING.

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WE DEPARTED SMF FOR SFO WITH A CRUISING ALT OF 9000 FT. DURING OUR CLBOUT; WE ENCOUNTERED SOME ICING. ONCE IN THE HOLD; WE CLBED UP TO 10000 FT TO GET OUT OF THE CLOUDS. AT 10000 FT; WE WERE ONLY OCCASIONALLY IN IMC CONDITIONS. ON OUR SECOND TURN IN HOLDING; I FELT THE ACFT SHUDDER/RUMBLE AND SCANNED THE ENG INSTS; WHICH WERE NORMAL. CAPT ADDED SOME PWR. SUBSEQUENTLY; THE ACFT SHUDDERED SOME MORE AND PITCHED DOWN. THE ACFT CONTINUED TO BE UNRESPONSIVE. I JOINED CAPT ON THE FLT CTLS; TRYING TO COUNTERACT THE ROLL. I DECLARED AN EMER WITH STOCKTON APCH. CAPT INCREASED PWR TO THE STOPS. THIS STILL HAD NO EFFECT ON THE ACFT. CAPT THEN CALLED FOR FLAPS 15 DEGS. I CONFIRMED THIS AND SELECTED FLAPS 15 DEGS. SHORTLY THEREAFTER THE ACFT STARTED TO RESPOND TO OUR INPUTS. I DID NOTICE THE AIRSPD PRIOR TO OUR LAST OUTBOUND TURN IN HOLDING AT SOMETHING ABOVE 160 KTS AFTER OUR CLB TO 10000 FT. THE SLOWEST I SAW THE AIRSPD DURING THIS WHOLE EVENT WAS BTWN 125-130 KTS. AFTER THE FIRST SCAN OF THE ENG INSTS I DID NOT NOTE ANY INSTS VALUES. I DO NOT REMEMBER LOOKING AT THE ALTIMETER DURING THIS EVENT. SUPPLEMENTAL INFO FROM ACN 395640: PICKING UP WHAT SEEMED TO BE LIGHT RIME ICE. ABOUT 1/2 WAY THROUGH THE TURN; STANDARD RATE; L 160 KTS; WE BOTH FELT A SHUDDER; ANOTHER; ADDED PWR. ACFT ROLLED STRONGLY TO THE L; AUTOPLT DISCONNECTED; MAY HAVE HAD THE STICK SHAKER; ADDED PWR; ATTEMPTED TO LEVEL WINGS AND REDUCE PITCH. ACFT ROLLED R; STILL SHUDDERING. FELT WE HAD POOR ROLL AND PITCH CTL; FIREWALLED PWR; SAW VARYING AIRSPDS; AS LOW AS 120 KTS. CALLED FLAPS 15 DEGS (THEY HAD BEEN UP) AND HAD TO CONFIRM IT. FO DID SELECT THEM WHEN HE WAS SURE I WANTED THEM. FLAPS 15 DEGS CAME FROM A PLT GROUP HANDOUT ON ROLL UPSETS. FEEL NEED TO CHANGE STALL TRAINING; ESPECIALLY RECOVERY.