* An engine running.
The ADMs supply an air heat signal to the power management panels when any of these conditions is true:
*
The airplane is in the air
*
Computed airspeed (CAS) is more than 50 kts.
The power management panels connect the ground heat and the air heat signals to current sense relays to control the voltage to the pitot probes. The ADMs monitor the pitot probe and AOA heaters through three electrical input discretes. The ADM transmits heater fault data on the flight controls bus.
For information on how to do a test of the pitot probe and the AOA sensor heat operation, see Ice and Rain Protection. (CHAPTER 30)
ADM Software Loading
The ADM can receive operational program software (OPS) from the AIMS cabinets through the flight controls ARINC 629 bus. You load the same software for pitot and static ADMs.
The ADM keeps the OPS in non-volatile memory (NVM).
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ADIRS -AIR DATA MODULE
Fault Data
The ADM sends fault and operational status data to the central maintenance computing function (CMCF) of the AIMS. The CMCF can command the ADM to test the pitot heaters and AOA heaters.
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777 AIRCRAFT MAINTENANCE MANUAL
ADIRS -AIR DATA MODULE
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ADIRS -SECONDARY ATTITUDE AIR DATA REFERENCE UNIT
General Standby Instruments
The secondary attitude air data reference unit (SAARU) is a The SAARU supplies attitude data to the standby attitude backup source of attitude and air data. indicator through the ARINC 429 bus.
Physical Description
The SAARU weighs 30 pounds. It uses passive cooling. Cooling fins take heat away from the SAARU.
Software Load
The SAARU can receive new software from the flight controls ARINC 629 data bus. The software data modifies the operational program of the SAARU.
Sensors and Circuits
The SAARU has these components:
*
Four fiber optic gyros
*
Four linear accelerometers
*
Two central processing units (CPUs)
*
Three ARINC 629 interface modules.
*
Two power supplies.
Three fiber optic gyros and three accelerometers are aligned with the roll, pitch, and yaw axis. The fourth fiber optic gyro and fourth accelerometer allow the SAARU to detect any faults in the other three.
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ADIRS -SAARU INERTIAL REFERENCE DATA FUNCTION
General
The secondary attitude air data reference unit (SAARU) uses gyros and accelerometers to calculate inertial reference data. The inertial reference data goes to airplane systems.
Power
The SAARU gets power from a circuit breaker in the center power supply assembly. The circuit breaker gets power from the center flight control DC bus.
Gyros and Accelerometers
The gyros and accelerometers measure rotation rates and accelerations. The rotation rates and accelerations go to buffers. The buffers supply the rotation rates and accelerations to the central processing unit which calculate SAARU data.
SAARU Data
The SAARU calculates this inertial reference data:
*
Body frame accelerations
*
Body frame angular rates
*
Attitude (roll and pitch)
*
Horizontal and vertical accelerations
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