WHEN THE PLT OF AN SMA SEL CLBED THROUGH THE FREEZING LEVEL THE ELEVATOR TRIM BECAME STUCK RESULTING IN AN AIRSPD DEV DURING DSCNT FOR APCH. THE TRIM BECAME UNSTUCK WHEN THE ACFT RETURNED BELOW THE FREEZING LEVEL.

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I PLANNED A NIGHT TRAINING FLT FROM RNT TO PAE AND RETURN; ON AN INST FLT PLAN. THE SURFACE TEMP WAS 39 DEGS F AND THERE WAS NO PRECIP; BUT THE AIRFRAME AND GND WERE WET DUE TO RAIN EARLIER IN THE DAY. THE FORECAST FREEZING LEVEL WAS 2000-3000 FT. I WAS NOT CONCERNED ABOUT INFLT ICING; SINCE MY RTE OF FLT WAS CLR. AFTER REACHING MY ASSIGNED ALT; I TRIMMED THE AIRPLANE FOR 130 KTS AND MADE A PIREP. THE OUTSIDE AIR TEMP WAS 29 DEGS F. I ATTEMPTED TO MAKE A MINOR ADJUSTMENT TO TRIM AND FOUND THE ELEVATOR TRIM FROZEN; THE WHEEL WOULDN'T MOVE. I WAS NOW TALKING TO ZSE; WAS TOLD I WAS #3 FOR THE APCH; AND TOLD TO CLB AND MAINTAIN 5000 FT. CTR THEN TOLD ME TO MAINTAIN 90 KTS. TO COMPLY; I REDUCED PWR AND LOWERED THE GEAR. WITHOUT THE TRIM THIS RESULTS IN A VERY NOSE HVY AIRPLANE THAT TAKES A WHILE TO DECELERATE. CTR THEN GAVE ME VECTORS TO THE LOC; AND A CLRNC FOR THE APCH; INCLUDING 'MAINTAIN 3000 FT UNTIL ESTABLISHED;' 3 MI FROM THE OM. DURING DSCNT FROM 5000 FT TO 3000 FT IT WAS DIFFICULT TO MAINTAIN 90 KTS; SINCE EVEN A SLIGHT RELAXATION IN BACK PRESSURE ALLOWED VERY RAPID ACCELERATION OF THE AIRPLANE. WHEN CTR CLRED ME FOR THE FREQ CHANGE TO TWR THEY AGAIN TOLD ME TO MAINTAIN 90 KTS. I TOLD THEM I'D TRY. I WAS CONCENTRATING SO HARD ON DOING THIS THAT IT DIDN'T OCCUR TO ME TO TELL THEM THE TRIM HAD FROZEN AND I WAS EXCEEDING THE 10 KT TOLERANCE. FROM THE OM INBOUND I WAS ABLE TO DO THIS; SINCE I HAD GOTTEN THE AIRPLANE STABILIZED. THE TRIM UNFROZE AT ABOUT 1000 FT; AND I ASKED FOR A CLRNC BACK TO RNT AT 2000 FT AND HAD NO PROBS. (IF THIS HAD HAPPENED IN IMC IT WOULD HAVE BEEN A REAL HANDFUL SINCE MY GS FAILED AT THE OM.) A LEAK AT THE BASE OF THE REAR WINDOW HAS BEEN SEALED.