FLT CREW OF GLF5; DISTR BY MULTIPLE FAILURES ANNUNCIATED ON THEIR MALFUNCTION WARNING SYS FAIL TO MONITOR FLT PATH AND CLB THROUGH CLRED ALT.

Narrative

I WAS THE FO; PNF OCCUPYING THE R SEAT OF A GV ON AN IFR REPOSITIONING FLT FROM GRR TO PBI. WE WERE TALKING WITH ZAU AND HAD BEEN CLRED DIRECT TO FWA VOR AND CLRED TO AN ALT OF FL190. AS WE PASSED THROUGH FL180 AND CHANGED OUR ALTIMETERS TO 29.92; WE BEGAN GETTING FAILURE MESSAGES ON OUR MESSAGE SCREEN. THE FIRST MESSAGE WAS ADC #1 FAIL FOLLOWED BY NUMEROUS OTHER MESSAGES WHICH WERE APPEARING AND THEN CLRING. WHILE TRYING TO INTERP WHAT WAS HAPPENING AND DETERMINE WHAT DATA WAS ACCURATE; WE CLBED THROUGH OUR ASSIGNED FL190 TO FL228. CHICAGO CALLED US AND ASKED OUR ASSIGNED ALT AT WHICH TIME WE RPTED THE FL228 WHERE WE HAD ARRESTED THE CLB. WE TOLD HIM OF OUR PROB AND ASKED FOR AN IMMEDIATE RETURN TO GRR AT WHICH TIME HE CLRED US TO TURN L DIRECT TO GRR AND THEN TO DSND TO LOWER ALT. WE WERE STILL UNSURE OF THE RELIABILITY OF OUR INSTS AND COMPARED THEM WITH OUR STANDBY INSTS UNTIL LNDG TO ENSURE ACCURACY. WE ALSO MADE GRR APCH AWARE OF OUT SIT AND HAD THEM MONITOR OUR GND PATH AND ALT READOUTS. FAILURE MESSAGES WERE APPEARING AND GOING AWAY SO RAPIDLY DURING THE EPISODE THAT WE WERE UNABLE TO DETERMINE WHAT THE MAIN PROB WAS. WE HAD AS MANY AS 10 FAILURE MESSAGES AT A TIME APPEARING. FAILURE TO LEVEL AT FL190 WAS CAUSED BY FAILURE OF THE AFCS COMPLICATED BY THE MULTIPLE OTHER FAILURES INCLUDING INSTRUMENTATION.