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What is an Air Data Computer?

Meaning | Concept | Definition:

An air data computer (ADC) is an avionics component that assimilates input from an aircraft’s external sensors and system and returns a series of calculated results critical to aircraft control. In one compact package, the Air Data Computer does what a bank of individual instruments was once required to do.

Nearly all of the flight-related information displayed on newer commercial aircraft equipped 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 great deal of aircraft system information beyond the normal flight envelope and navigational functionality.

An air data computer synthesizes the information obtained from the various sensors on an aircraft.

The cockpits of older aircraft featured a large number of individual instruments displaying all the information pilots needed to safely and accurately fly the aircraft and navigate the flight path. These instruments used pitot inputs, static air pressure, and system sensors mounted on and around the exterior of the aircraft to supply the necessary inputs to power them.

In the late 1960s, a groundbreaking military project saw the installation of the first single device that took those inputs and provided all the information in a compact package. Installed on the F14A Tomcat fighter, the Central Air Data Computer (CADC) revolutionized the concept of cockpit information transmission and established the cornerstone of modern ADC technology.

Air data computers can be thought of as marshalling stations for the large number of system and environmental sensor inputs that supply critical flight data in modern aircraft. All of these inputs are used by the computer to extrapolate a series of real-time results that are then displayed on one or more display units (DUs) in the cockpit.

Flight envelope and environmental information typically include true and indicated airspeeds, ground speed, altitude, rate of climb, total and static air temperatures, and density altitude variables, among others.

Positional reference can also be included in 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 this unique computing power has evolved to the point where these systems are no longer the preserve of Boeing and Airbus and are available as small, powerful retrofit units for smaller aircraft.

These panel-mounted units can return all of the functionality mentioned above, either on an integral or separate display, making even small general aviation aircraft safer and more efficient.

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