A HAWKER BAE125-800A IN CRUISE AT FL370 ENCOUNTERED A TSTM RESULTING IN LOSS OF ENVIRONMENTAL SENSING CAUSING AN ALTDEV.

Narrative

WHILE IN CRUISE AT FL370; WE ENCOUNTERED THE TOP OF A TSTM. WX RADAR DID NOT DETECT THE STORM. WE FLEW THROUGH AN AREA OF SUPERCOOLED RAIN; ICE; AND SNOW. AFTER PASSING THROUGH THIS AREA; THE AUTOPLT DISCONNECTED AND THE PLT'S PITOT STATIC INDICATIONS WERE LOST (PITOT STATIC HEAT WAS OPERATIONAL). THE L AUTOMATIC FLT CTL SYS WAS INOP ALONG WITH THE R AUTOMATIC FLT CTL SYS. PITOT STATIC INDICATIONS ON THE R (COPLT'S) BECAME ERRATIC. THE CAPT RELINQUISHED CTL OF THE ACFT TO ME. THIS SEQUENCE OF EVENTS OCCURRED IN LESS THAN 60 SECONDS. DUE TO THE TURB ASSOCIATED WITH THE WX; THE LOSS OF THE L AND R AUTOMATIC FLT CTL SYS AND THE ASSOCIATED DIFFICULTIES OF FLYING AN ACFT AT FL370 WITHOUT A FLT DIRECTOR A LOSS OF 500 FT OCCURRED. AFTER A SHORT PERIOD OF TIME (5 MINS) WE REGAINED USE OF THE AUTOMATIC FLT CTL SYS. ATC WAS NOT ADVISED NOR DID THEY ADVISE US OF THE DEV. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE PITOT AND STATIC HEAT WAS OPERATIVE AND SWITCHED ON AT THE TIME OF THE INCIDENT. THE RPTR SAID THE FO'S FLT INSTS; ALTIMETER AND AIRSPD INDICATOR WERE OPERATIVE THROUGHOUT THIS EVENT. THE RPTR SAID THE INSTS WERE DRIVEN BY AIR DATA COMPUTERS L AND R. THE RPTR STATED THE HAWKER 800 HAD A HISTORY OF THIS TYPE OF ANOMALY WHERE ENVIRONMENTAL DATA WAS LOST IN TURB. THE RPTR SAID MAINT WAS UNABLE TO VERIFY THE RPT AND ALL SYS CHKED OK.