Which inputs are processed by the Air Data Computer (ADC) to compute altitude and airspeeds?

• A. Pitot pressure, static pressure, and temperature
• B. GPS coordinates, magnetic heading, and altitude
• C. Altitude only
• D. VOR radial and distance

Answer: (A)

The Air Data Computer relies on three measurements to determine altitude and airspeeds: pitot (total) pressure, static pressure, and temperature. Pitot pressure gives the total pressure the air exerts when the aircraft is moving, while static pressure represents the ambient atmospheric pressure. The ADC uses the difference between pitot and static pressure to compute dynamic pressure, which is directly related to indicated airspeed. At the same time, static pressure data set the baseline for altitude calculations, and the temperature input allows corrections for the actual air density, enabling accurate true airspeed and density altitude calculations. Temperature is essential because air density—and thus how airspeed translates to actual speed—varies with temperature. Signals like GPS coordinates, magnetic heading, and VOR/DME data are used for navigation, not for calculating air data, and altitude alone isn’t enough without the dynamic pressure information from pitot and the temperature context.