Air Data Computer (ADC)

Wg Cdr Rajagopal

Air Data Computer

Index

Requirement of Air Data Computer

  • Avoid multiple Pitot and Static lines
  • Provide centralized source of static and pitot pressure
  • Convert pressure data in an electric or electronic format

Advantage of Air Data Computer

  • Provide pressure data to other equipments
  • Flight data recorder
  • Navigation computer
  • Auto Pilot

Equipments dependent on Air Data Computer

  • ADC provides pressure data to
  • Flight Data Recorder
  • Electronic Flight Information System
  • Warning Systems
  • ATC Transponder
  • Inertial Reference System
  • Flight Control Computer
  • Flight Management System

Analogue ADC

  • Analogue ADC
  • E-I bar to convert pressure data to electrical inputs
  • Pressure information is transmitted through Pressure Transducer

Digital ADC

  • Digital ADC
  • Analogue to digital interface units
  • Pressure information is transmitted through Digital Bus Bar

Configuration Module

  • Configuration module corrects for position error
  • Built in test equipment called BITE test
  • Power up Check Up on start up
  • Continuous Monitoring every one second
  • Maintenance Tests during servicing or post-mortem

System Redundancy

  • Redundancy to cater for blockage or leaks
  • Electrical change over to use alternate static source
  • Captain’s pressure sensors can provide data to Co-pilot’s equipments

Failure Warning in ADC

  • Failure warning by Comparison monitor
  • Warning Flag in case of loss of valid data or internal failure
  • Comparison of outputs of Left and Right ADC components
  • Light on the Instrument warning panel

Advantages of Air Data Computer

  • Advantages of ADC over conventional Pitot Static system
  • Improved Displays like digital, moving tape and combined displays
  • Reduced Instrument and Lag Errors using servo motors.
  • Error Correction by comparison of multiple inputs
  • Height and airspeed channel for additional equipments
  • Central pressure data Source for Other Systems
  • Clean Design and Better Maintenance

Inputs – Outputs of ADC

  • Inputs
  • Pitot pressure
  • Static pressure
  • Total air temperature
  • Angle of attack
  • Weight on wheels switch
  • Main power source
  • Backup power source
  • Outputs
  • Altitude
  • Vertical speed
  • IAS or CAS
  • SAT
  • TAS
  • Mach number
  • Angle of attack

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