*
1 power supply
*
2 processors
*
1 ARINC 629 I/O module in the left and right FCA.
This happens if there are more than two failures in an FCA:
* The ADIRU does not supply inertial reference data
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ADIRS -ADIRU RELIABILITY AND FAULT TOLERANCE
*
The status message ADIRU shows
*
The EICAS caution message NAV ADIRU INERTIAL shows
*
The ADIRU sends data to AIMS to make a maintenance message show on the MAT.
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ADIRS -ADIRU RELIABILITY AND FAULT TOLERANCE
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ADIRS -ADIRU POWERUP, ON BATTERY, POWERDOWN
PFC/ADIRU Panel
The primary flight computer (PFC)/ADIRU panel has the ADIRU switch and the ADIRU on battery (ON BAT) light.
The ADIRU switch has five sets of contacts. Three of these contacts send discrete inputs to the ADIRU power and monitor circuit. One contact supplies a ground for the ADIRU OFF light, or a ground to energize the relay to make the ground crew call horn come on. The last contact makes the ADIRU ON light come on.
ADIRU Power Source
All the ADIRU power inputs go to the ADIRU power supply. This power goes to the power and I/O (input/output) monitor. The power and I/O monitor verifies the ADIRU switch inputs. If the ADIRU switch is in the on position, the power and I/O monitor permits the power to go to the ADIRU processors.
Ground Crew Alert
If the ADIRU loses primary power, it uses the airplane battery and the ADIRU ON BAT light comes on. The ground crew call horn comes on when the airplane is on the ground and the only source of power for the ADIRU is the hot battery bus. The ground crew call horn comes on to alert the ground crew that the hot battery bus is the only source of power for the ADIRU.
The ADIRU ON BAT light and the ground crew call horn come on if all these conditions are true:
*
Battery switch is in the off position
*
Ground service relay is in the off position
*
Air/ground relay is in the ground position
*
The ADIRU switch is in the on position.
Power Down
With the ADIRU switch in the off position, one of these conditions must be present before the ADIRU will power down:
*
Ground speed is less than 20 kts
*
Computed airspeed is less than 30 kts.
All three power off discretes from the ADIRU on/off switch must be present for shutdown.
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777 AIRCRAFT MAINTENANCE MANUAL
THIS PAGE IS INTENTIONALLY LEFT BLANK
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ADIRS -ADIRU AIR DATA FUNCTION -1
General
Redundancy management logic in the ADIRU selects a value from the inputs that come from more than one source. This makes sure that the ADIRU uses only valid data.
Total Air Temperature
The total air temperature (TAT) redundancy management logic calculates an average of the TAT values from TAT inputs 1 and
2.
Pitot Pressure
Pitot pressure comes from the left, center, and right pitot air data modules (ADMs). The pitot ADM redundancy management logic uses mid-value selection to choose one of the pitot pressure inputs. The redundancy management logic also finds if any of the signals are not valid.
AOA Heater Valid
The angle of attack (AOA) heater valid signals go to the AOA redundancy management logic. The AOA redundancy management logic uses the AOA heater valid signal to find if the AOA sensors are valid.
AOA Input
The AOA values go to the calculate corrected AOA function.
EFFECTIVITY
BEJ ALL
Speedbrake Lever Past Arm Signal
The primary flight computers (PFCs) supply the speedbrake lever angle signals to the ADIRU. An input data redundancy management logic selects one of the PFC signals. The speedbrake lever past arm signal goes to the AOA redundancy management logic.
Air/Ground, Nose Gear Position, and Flap Angle
The proximity sensor electronics units (PSEUs) supply the air/ ground and the nose gear position signals to the AIMS cabinets.
The flap/slat electronic units (FSEUs) supply the flap angle signals to the AIMS cabinets. The AIMS cabinets supply the signals to the ADIRU.
The input data redundancy management logic chooses the left PFC input data first, then center if the left fails, then the right if the left and center fail. The redundancy management also chooses PSEU and FSEU number 1 input first. If the number 1 input fails, then it chooses the number 2 input.
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