What was found
AIRCRAFT WAS GROUNDED: AT CRUISE ALTITUDE 33, WITH ALL ENGINE AND WING HEAT ON THE MACH TRIM, INOPERABLE LIGHT ILLUMINATED, AIRSPEED/MACH INDICATION. EMERGENCY WAS DECLARED INBOUND TO BNA, REMAINDER OF THE FLIGHT CONTINUED WITHOUT AUTOPILOT AND AUTOTHROTTLES USING STANDBY MACH/AIRSPEED INDICATORS. MAINTENANCE REPLACED NR 1 CENTRAL AIR DATA COMPUTER PER MM 34-16-01 AND PERFORMED SATISFACTORY OPERATIONAL CHECKS.