SMA ENCOUNTERS ICING; UNABLE TO SUSTAIN ALT. REQUESTED LOWER; UNABLE; DECLARES EMER. MAKES EMER LNDG AT RDU.

Narrative

I WAS ON AN IFR FLT PLAN FROM OPF TO DCA IN A HVY; IMC AT ALT OF 11000 FT AT ABOUT 40 MI S OF RDU. I NOTICED THAT MY AIRSPD INDICATOR THAT USUALLY GIVES A READING OF ABOUT 150 KTS; GAVE A READING OF 125 KTS. PRIOR TO ENTERING IMC I TURN ON ALL DE-ICE AND ANTI-ICE EQUIP. UPON ENTERING IMC I NOTICED THAT THE AIRSPD BEGAN TO DECREASE. I XCHKED MY PWR AND MY PITCH AND THEY SEEMED TO BE NORMAL WITH THE EXCEPTION OF MY AIRSPD INDICATOR. I SUSPECTED ICE ACCUMULATION IN THE PITOT TUBE. I THEN REQUESTED LOWER ALT FROM ZDC. ADC DENIED MY REQUEST FOR DSCNT AND INFORMED ME THAT IT WILL TAKE A FEW MINS DUE TO HVY TFC. AT THAT TIME; I NOTICED MY AIRSPD DECREASE TO 90 KTS; I THEN CALLED ZDC AND INFORMED THAT I NEED AN IMMEDIATE DSCNT. THEY ASKED ME IF I WOULD LIKE TO DECLARE EMER WHICH I DID. THEY CLRED ME TO 8000 FT AND HDG CHANGE OF 90 DEGS TO THE R (080 DEGS); AT 8000 FT I WAS STILL IMC SO THEY CLRED ME TO 6000 FT TO VMC CONDITIONS. THROUGHOUT THE DSCNT MY AIRSPD INDICATED 0 KTS. I WAS VECTORED TO RDU WHERE I MADE NORMAL LNDG ON RWY 23L. AN INSPECTION ON THE GND AT RDU DISCOVERED A LOOSE WIRE IN THE PITOT TUBE HEATING ELEMENT. THE TECHNICIAN FIXED THE WIRING AND THE PROBLEM WAS SOLVED. THE ACFT WAS RECENTLY (2 WKS PRIOR TO THIS INCIDENT) PURCHASED AND WENT THROUGH PRE-PURCHASE INSPECTION. I SUSPECT THAT REMOVAL OF THE PITOT MAST CAUSED THE WIRES TO COME LOOSE.