What was found
AIRCRAFT WAS GROUNDED: ON DESCENT OUT OF FL300 IN IMC CONDITIONS GOT IAS DISAGREE. FOS AIRSPEED/MACH INDICATED 8 KIAS .5 MACH LOW. HAPPENED SEVERAL TIMES BETWEEN FL300 AND FL200 THEN CORRECTED. MAINTENANCE TROUBLESHOT IAW FIM 31-62-00. BITE CHECKED ADIRU AND CDS. HAD 31-65060 FAULT. CHECKED PITOT AND STATIC FOR BLOCKAGE, LEAKS AND MOISTURE. HEATERS ALL NORMAL. REPLACED RIGHT AOA IAW AMM 34-21-05. ALL OPS CHECKS ARE NORMAL.