AFTER TKOF; A D328 FO EXPERIENCED WILD FLUCTUATIONS ON PITOT-STATIC INSTS. THE CAPT TOOK THE CTLS AND THE FLT RETURNED AND LANDED.

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AFTER TKOF AT ABOUT 100 FT AGL; FO (FLYING) NOTICED HIS AIRSPD INDICATOR TO BE ERRATIC AND DROP TO 60 KIAS. MY AIRSPD SHOWED 180 KIAS. FO'S ALTIMETER ALSO WAS ERRATIC. I TOOK THE CTLS AND WE MADE A TFC PATTERN AND RETURNED TO THE FIELD VISUALLY. WE STAYED VMC; LANDED UNEVENTFULLY. WE DIDN'T DECLARE AN EMER. THE DORNIER 328 HAS AN ALL- GLASS COCKPIT. WE BELIEVE THAT THE AIR DATA COMPUTER #2 FAILED DUE TO ICE AND FREEZING RAIN IN PITOT-STATIC SYS. ACFT WAS PARKED OVERNIGHT OUTSIDE. THIS WAS THE 1ST FLT OF THE DAY. WE HAD SNOW AND FREEZING RAIN THE NIGHT BEFORE. MAINT PERSONNEL RAN UP ACFT AND APPLIED HEAT TO SYS AND ACFT WAS OK LATER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: FLC OF THE D328 HAD FLOWN AND LANDED IN SNOW CONDITIONS THE NIGHT BEFORE. PITOT TUBES AND STATIC PORTS WERE WX PROOFED AFTER SHUTDOWN; BUT THE CAPT (RPTR) BELIEVES THAT THE AIRPLANE HAD RESIDUAL MOISTURE WHICH FROZE WHEN THE ACFT WAS COLD SOAKED DURING THE NIGHT. RPTR STATES THAT THIS HAPPENED TO BE ONE OF THE ARPTS WHERE THEY DID NOT HAVE THE ACFT HANGARED. IN THE MORNING; THE ACFT HAD BEEN DEICED AND PAX BOARDED. DURING THE FIRST FLT OF THE DAY CHKS; THE AURAL STALL WARNING; INITIALLY; WAS STUCK ON; BUT THEN IT OPERATED NORMALLY. THE STUCK STALL WARNING MADE THE RPTR WELL AWARE OF THE ACFT'S FROZEN CONDITION. EVEN THOUGH THE FLC RECEIVED AN ADC (AIR DATA COMPUTER) FAIL MESSAGE; THE CAPT STATES THAT THE PROB WAS STRICTLY RELATED TO THE PITOT-STATIC INFO THAT WAS SENT TO THE ADC. THE ADC CHKED NORMAL DURING GND TEST BEFORE AND AFTER THIS FLT. THE PROB (WILDLY FLUCTUATING PITOT-STATIC INSTS) WAS RECOGNIZED BY THE FO IMMEDIATELY AFTER TKOF AND WAS CALLED TO THE CAPT'S ATTN. AFTER RETURN AND LNDG; MAINT RAN THE ACFT HEAT ON THE APU. AFTER THE ACFT WAS THAWED AND DEICED; ALL CHKS WERE NORMAL. THE ACFT WAS CLRED FOR A FERRY FLT AND THERE WERE NO FURTHER PROBS.