SMA LOST PWR DUE TO ICE THAT FORMED IN THE CARB INDUCTION TUBE.

Narrative

PREFLT INSPECTION (STUDENT AND CFI) -- NO DISCREPANCIES NOTED. RUN-UP NORMAL. TKOF AND CLB -- NORMAL ENG PWR OUTPUT. FIRST TOUCH-AND-GO NORMAL. SECOND TKOF AND CLB; NORMAL OPS. THROTTLE REDUCTION ON DOWNWIND FROM 2500-2100 RPMS ROUGH RUNNING ENG ACFT 'SHAKING'. PWR LOSS CHKLIST ACCOMPLISHED. CARB HEAT -- UNABLE TO OPEN LEVER FULLY (APPROX 1/3 TRAVEL OBTAINED). CONDITION WORSENED. MORE LOSS OF PWR AND MORE VIBRATION NOTED. CONTACTED TWR FOR FULL STOP LNDG -- NO EMER DECLARED. ADJUSTED THROTTLE SLIGHTLY. NO CHANGE IN PERFORMANCE. CLOSED AND TRIED TO OBTAIN CARB HEAT. CONDITIONS WORSENED (WITH 0 CARB HEAT). LANDED UNEVENTFULLY. TAXI WAS UNEVENTFUL. ENG STILL VIBRATING AND RPM'S DECREASED SLIGHTLY. TRIED TO OPEN CARB HEAT (WITH FORCE) AND SUCCEEDED. ENG RAN SMOOTHLY. RESISTANCE NOTED WHILE ATTEMPTING THE ABOVE; THE A 'SNAP.' THEN ENG RAN WELL. TAXIED TO MAINT FACILITY. A&P LISTENED TO THE EVENT. NOTED WATER IN CARB. REMOVED TUBING FROM INDUCTION AIR FILTER (FOAM TYPE) TO AIR BOX. LARGE CHUNK OF ICE FELL OUT. RUN-UP AND SUBSEQUENT OPS ALL OKAY. PRIOR TO FLT WE HAD HVY RAIN AND SNOW DURING THE PRECEDING DAY. TEMPS NEVER GOT OVER 0 DEGS C.