What is an Air Data Computer? (original) (raw)

An air data computer (ADC) is a avionics component that assimilates the inputs from an aircraft's external and system sensors and returns a series of calculated results critical to the control of the aircraft. In one compact package, the air data computer performs what a bank of individual instruments were once required to do. Almost all the flight-related information displayed in newer commercial aircraft fitted with glass cockpits is compiled by an air data computer. These computers are also available for smaller commercial and private aircraft as compact, panel mounted units with integral graphic displays. They are often sophisticated enough to provide a wealth of aircraft system information over and above the normal flight envelope and navigational functionality.

Older aircraft cockpits featured large numbers of individual instruments which displayed all the information needed by the pilots to safely and accurately fly the aircraft and navigate the flight route. These instruments used inputs from pitot, static air pressure, and system sensors mounted in and around the aircraft's exterior to supply the inputs needed to drive them. During the late 1960s, a groundbreaking military project saw the installation of the first single device which took those inputs and supplied all the information in one compact package. Installed in the F14A Tomcat fighter, the Central Air Data Computer (CADC) revolutionized the concept of cockpit information streaming and set the cornerstone for modern ADC technology.

Air data computers may be thought of as marshaling yards for the host of environmental and system sensor inputs which supply critical flight data in modern aircraft. The computer uses all these inputs to extrapolate a series of real time results which are then displayed on one or more display units (DUs) in the cockpit. Flight envelope and environmental information typically includes true and indicated airspeeds, ground speed, altitude, rate of climb, total and static air temperatures, and density altitude variables among others. Positional referencing may also be included in the ADC outputs through interfaces with global positioning satellite (GPS) and inertial reference systems (INS) and internal calculations of wind drift factors.

Aircraft system information such as engine parameters, electrical and hydraulic systems, cabin temperature, and pressure and fuel quantity and temperature are also displayed on the DUs by the air data computer. The technology involved in all of this one-stop computing power has evolved to the point where these systems are no longer the exclusive reserve of Boeing and Airbus and are available as small and powerful retrofit units for smaller aircraft. These panel mounted units can return all of the previously mentioned functionality either on an integral or a separate display, thereby making even small, general aviation aircraft safer and more efficient.

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