PLT OF A C182 FLEW INTO ICING CONDITIONS DURING SHORT IFR FLT CAUSING LOSS OF AIR AND VERT SPD INDICATORS DUE TO THE PITOT TUBE ICING OVER. PLT DECLARED PROB TO ARTCC CTLR AND WAS ASSISTED OUT OF ICING AND TO A SUCCESSFUL LNDG.

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PROB AROSE ON A NIGHT IFR 6000 FT CRUISE VMC/MARGINAL 50 MI FLT WHILE WORKING ZID ON FREQ 124.22 WHEREIN WE EXPERIENCED UNEXPECTED LIGHT TO MODERATE SNOW/RAIN IMC CONDITIONS ACCOMPANIED WITH VERY HVY STATIC ON THE FREQ. DISTR TO TROUBLESHOOTING THE STATIC CAUSES; DELAYED SEVERAL MINS IN TURNING ON PITOT HEAT. OUTSIDE AIR TEMP WAS +5 DEGS; SO ASKED FOR 4000 FT SEEKING WARMER OUTSIDE AIR TEMP. AIRSPD INDICATION FAILED INDICATING ICE/UP; VSI STUCK ON ZERO DURING DSCNT TO 4000 FT AND ALTIMETER INDICATION (RATE OF NEEDLE MOVEMENT DURING DSCNT) WAS ERRATIC. PULLED ON ALTERNATE AIR; BUT THERE SEEMED TO BE A BLOCKAGE IN THE PUSH/PULL SWITCH WHEREIN THE SWITCH COULD BE PULLED OUT (ON) BUT PUSHED ONLY PARTIALLY IN TO THE OFF POS. IT HAD APPARENTLY BEEN IN A 1/2 WAY POS AND THE PITOT HEAD HAD FROZEN UP. OUR CRUISE FLT WAS ON AUTOPLT (S-TEC 30) ALT HOLD AND ON ARR AT 4000 FT FROM DSCNT OUT OF 6000 FT THE AUTOPLT ALT HOLD FAILED TO ENGAGE; RESULTING IN CONTINUING DRIFTDOWN TO 3600 FT; AND CTR CTLR CALLED FOR ALT RPT AND WE CONFIRMED. I DECLARED OUR PITOT STATIC PROBS AND WE COMPARED MODE C READOUTS TO ESTABLISH THE AIRPLANE BACK TO 4000 FT. ZID ADVISED HE WOULD LET DEST APCH CTL KNOW OF OUR PROB; CHANGED US OVER 40 MI OUT. WE CONTINUED TO DEST IN VMC FOR A VISUAL APCH. AIRSPD WAS STUCK ON 170 KTS FOR LNDG. AFTER DEPLANING; I TELEPHONED LEX TWR TO ASK CTLR IF THERE WAS ANY CONFLICT WITH TFC; APCH CTL; OR CTR. HE ADVISED 'NO PROB.' WE OBTAINED MAINT FOR THE NEXT FLT.