Plain English Meaning

Small onboard computers that take pressure and temperature readings from outside the aircraft and turn them into the altitude, airspeed, and other air-related numbers shown to the pilot and used by autopilot and altitude-reporting systems.

Full Definition

Air data computers are electronic units that take raw inputs from the aircraft's pitot-static system and outside air temperature probe, then calculate and output processed air data values such as pressure altitude, indicated airspeed, true airspeed, Mach number, vertical speed, and static air temperature. In RVSM-equipped aircraft, two independent ADCs feed the altimetry to ensure the precise altitude-keeping required for operations in reduced .