PLT OF AN SMA SEL MOMENTARILY LOST CTL OF THE ACFT DURING DSCNT IN ICING CONDITIONS DUE TO THE PITOT STATIC SYS ICING UP CAUSING LOSS OF BASIC FLT INSTS.

Narrative

WHILE INITIATING AND EXECUTING DSCNT FROM 11000 FT TO 6000 FT AND ON VECTORS SLIGHTLY L OF V2 FOR A VFR LETDOWN TO S-50; AND ON AN IFR FLT PLAN IN ACTUAL NIGHT CONDITIONS (IFR); ENCOUNTERED MODERATE RIME ICING AT ABOUT 8000 FT. THE AIRSPD INDICATED 160 KTS; THE GPS INDICATED 94 KTS. THE DME INDICATED 95 KTS. I HAD A CRAB ANGLE OF 15 DEGS L TO MAINTAIN PRESENT HDG. LIGHT TO MODERATE TURB AND A MODERATE BUILDUP OF ICE ON AIRFRAME. UPSLOPE ICING WAS IN FORECAST. COLD FRONT LOCATED ON WINDWARD SIDE OF CASCADES WHERE I WAS. I ATTEMPTED TO ARREST 2000 FT A MINUTE DSCNT RATE AT 7000 FT FOR A SLOWER RATE TO 6000 FT. AS I WAS ATTEMPTING TO RAISE THE NOSE (ATTITUDE) ON THE ATTITUDE BAR OF ATTITUDE INDICATOR TO 0 DEGS WHICH I DID; I THINK THE MODERATE ICING BLOCKED THE PIPER PA32T HEATED PITOT (WHICH WAS ON AS I HAVE A LIGHT ON THE PANEL) INDICATING IT WAS ON. THE VSI; THE ALTIMETER AND THE AIRSPD MOMENTARILY DUMPED ABOUT 600 FT BACKWARDS; THEN FORWARD. THE AIRSPD I WAS NOT LOOKING AT IT; AS I WAS SORTING OUT WHICH INSTS WERE RIGHT. I HIT THE ALTERNATE AIR LEVER WHICH STABILIZED THE ALTIMETER AND THE VSI. THE CTLR CAME ON ASKING ME IF I HAD A PROB. I DID NOT ANSWER. (I 'BLEW' THROUGH ALT ABOUT 300 FT LOWER.) WHEN I HAD THE PLANE UNDER CTL; I CLBED BACK TO 6000 FT AND TOLD THE CTLR 'I HAD A LITTLE ICING PROB.' THE REST OF THE FLT WENT NORMAL AND I LOST THE ICE AT ABOUT 5000 FT; BROKE OUT OF THE CLOUDS AT 4000 FT; THEN ON TO S-50; 10 MI TO THE W. MORAL OF THE STORY: DON'T FLY ON THE UPSLOPE OF THE CASCADES WITH A COLD FRONT 'CAMPING OUT' THERE WITH A 'NO ICE PROTECTION' AIRPLANE. THIS WAS A DUMB MOVE -- I ASKED FOR IT.