Outputs
The ADIRU transmits air data to the left and right flight controls ARINC 629 buses. The air data goes to these components:
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Left and right AIMS cabinets
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Left, center, and right primary flight computers (PFCs)
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Left, center, and right autopilot flight director computers (AFDCs).
Only one of the two connections to each flight controls ARINC 629 bus is active at a time.
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General
The ADIRU uses data from the flight management computing function (FMCF) in the AIMS cabinets to do these functions:
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Initialize the airplane position
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Calibrate the gyros and accelerometers.
Inputs
The FMCF sends this data to the inertial reference function in the ADIRU:
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Initial position
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Airplane type
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Global positioning system (GPS) position (longitude and latitude)
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GPS velocity (north, east, and vertical).
Initial Position
When the flight crew enters the initial position on the control display unit (CDU), the position goes to the FMCF of the AIMS. The AIMS sends the entered initial position to the ADIRU. The ADIRU’s initial position validation logic does this:
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Verifies the validity of the entered initial position
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Compares the entered initial position to the global position system (GPS) position or the last ADIRU stored position if GPS data is not available.
If the entered initial position is good, the ADIRU uses it as the initial position for alignment.
Gyro and Accelerometer Calibration
The GPS position and velocity go to the sensor calibration logic. The sensor calibration logic supplies calibration data to the gyros and accelerometers. The calibration does not correct the ADIRU errors. It only reduces ADIRU drift errors as the airplane flies.
If the GPS position is not valid, there is no source of calibration data for the gyros and accelerometers.
Gyros and Accelerometers
The gyros send rotational rate data to the inertial reference calculation. The accelerometers send linear accelerations to the inertial reference calculation.
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Wind Speed and Wind Direction
True airspeed data from the ADIRU air data function goes to the calculate wind speed and calculate wind direction function.
Pitch Rate, Roll Rate, Yaw Rate
The ADIRU uses the rotational rates from the six gyros to calculate:
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Pitch rate
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Roll rate
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Yaw rate.
Pitch Angle, Roll Angles, True Heading, Air data Function
The rotational rates from the six gyros go to the angles integrator. The angles integrator function calculates the airplane:
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Pitch angle
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Roll angle
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True heading.
Magnetic Heading And Magnetic Track
Rotational rates and linear accelerations go to the rotate accelerations to earth reference function. The rotate accelerations to earth reference function calculates accelerations in relation to the earth.
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The accelerations in relation to the earth go to the velocities integrator. The velocities integrator calculates velocities. The velocities go to the position integrator and the calculate magnetic parameters function.
The position integrator calculates airplane position.
The calculate magnetic parameters uses the following data:
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Position integrator
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Velocities integrator
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Angles integrator.
The magnetic heading and magnetic track go to the output memory buffer only when the magnetic track is valid, and the ground speed is more than 20 knots.
Drift Angle
The velocities integrator sends data to the calculate drift angle circuit.
The drift angle goes to the output memory buffer only when the drift angle is valid and the groundspeed is more than 20 knots.
Latitude and Longitude
The velocities integrator sends velocities to the position integrator. The position integrator sends latitude and longitude to the output memory buffer.
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