AN SMA TWIN PLT OVER CTLED HIS ACFT IN IMC.

Narrative

AT DEP; THE CONDITIONS AT FPR WERE 1500 FT SCATTERED AND THE FORECAST WAS FOR VFR CONDITIONS WITH GOOD VISIBILITY AT THE TIME OF OUR ARR. OUR FLT AT 7000 FT WAS OVER VARIABLE CONDITIONS; CLR TO SCATTERED TO BROKEN BENEATH US AND CLR ABOVE. ABOUT 10-15 MINS OUT OF FT PIERCE WE GOT THEIR ATIS INFO THAT INDICATED 4000 FT BROKEN WITH GOOD VISIBILITY. SHORTLY AFTER PASSING THE PRESK INTXN; WE WERE CLRED TO 6000 FT AND DIRECT TO FPR. ZMA CLRED US TO 3000 FT AND TOLD US TO EXPECT A VISUAL APCH. I STOWED THE APCH PLATES; A VERY SERIOUS ERROR AND A LEARNING EXPERIENCE; STARTED A DSCNT AND WAS IMC BEFORE 5000 FT. AT 3000 FT; I TOLD THE CTR WE WERE STILL IMC AND WAS CLRED TO 2000 FT. AT 2000 FT WE WERE STILL IMC. I ADVISED THE CTR AND WAS GIVEN A HDG FOR VECTORS TO THE NDB 9 APCH TO FPR. AS I REACHED FOR THE APCH PLATES AND THE SWITCH TO ENGAGE THE HDG BUG; I INADVERTENTLY DISENGAGED THE AUTOPLT. THE NOSE OF THE AIRPLANE PITCHED UP. THE THOUGHT OF THE LOAD IN THE PLANE AND THE POSSIBILITY OF A STALL FRIGHTENED ME AND I PUT ALL MY EFFORTS INTO GETTING THE NOSE DOWN. WHEN THE ELECTRIC TRIM TOOK EFFECT; I MUST HAVE OVER CTLED BECAUSE WE THEN WERE IN A DSCNT THAT EXCEEDED 1500 FPM FOR A FEW SECONDS. WE SUDDENLY FLEW INTO A CLR AREA AND I; RATHER BADLY SHAKEN; REDUCED THE PWR AND MADE A QUICK DSCNT WHILE WE WERE IN THE CLR IN ORDER TO GET BELOW THE CEILING. I TOLD THE CTLR WE WERE IN THE CLR AND SHE TURNED ME OVER TO THE FPR TWR. AS WE CONTACTED THE TWR; HE INFORMED ALL PLTS THAT THE CEILING WAS NOW 900 FT AND THE FIELD WAS IFR. WE LANDED WITH NO FURTHER PROBS.