777 AIRCRAFT MAINTENANCE MANUAL
ADIRS -AIR DATA/ATTITUDE SOURCE SWITCH
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ADIRS -AIR DATA/ATTITUDE SOURCE SWITCHING-NON NORMAL
General * SAARU center flight controls ARINC 629 bus (air data and attitude) The table shows the normal and alternate positions for the * ADIRU right flight controls ARINC 629 bus (single channel air data)
captain and first officer air data/attitude switch during normal * ADIRU left flight controls ARINC 629 bus (single channel air and non-normal conditions.
data).
The fail condition means that all output data to the buses are invalid.
Display Switching Priorities
These are the priorities for the source of the captain attitude and air data displays:
*
ADIRU left flight controls ARINC 629 bus (air data and
attitude)
*
ADIRU right flight controls ARINC 629 bus (air data and
attitude)
*
SAARU center flight controls ARINC 629 bus (air data and
attitude)
*
ADIRU left flight controls ARINC 629 bus (single channel air
data)
*
ADIRU right flight controls ARINC 629 bus (single channel air
data).
These are the priorities for the source of the first officer attitude and air data displays:
*
ADIRU right flight controls ARINC 629 bus (air data and
attitude)
*
ADIRU left flight controls ARINC 629 bus (air data and
attitude)
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
ADIRS -AIR DATA/ATTITUDE SOURCE SWITCHING-NON NORMAL
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ADIRS -ADIRU SWITCH, ADIRU ON BATTERY LIGHT
General
The primary flight computers/ADIRU panel has the ADIRU switch and the ADIRU on battery light.
ADIRU On Battery Light
The ADIRU on battery light comes on when the airplane is on the ground and the only source of power for the ADIRU is the hot battery bus.
ADIRU Switch
Push the ADIRU switch to make the ADIRU go on. About thirty seconds after you push the ADIRU switch to the ON position, the ADIRU begins alignment. During the initial alignment, the attitude indications on the PFDs show as no computed data (NCD).
Push the ADIRU switch again to make the ADIRU go off.
The ADIRU goes off only when:
*
Ground speed (GS) < 20 kts
*
Computed airspeed (CAS) < 30 kts.
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ADIRS -ADIRU SWITCH, ADIRU ON BATTERY LIGHT
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777 AIRCRAFT MAINTENANCE MANUAL
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ADIRS -ALIGNMENT
General
To supply inertial position data, the ADIRU must be in the navigation (NAV) mode. Before the ADIRU enters the NAV mode, it must go through alignment and position initialization. Both of these occur during the align mode. The ADIRU goes to the align mode from one of these modes:
*
Initialization mode
*
Align reset mode
*
Auto nav realign mode.
Initialization Mode
Within one minute after you push the ADIRU switch to the ON position, the ADIRU enters the align mode. While the ADIRU is in the align mode, the CDU shows box prompts on line data field 5R of the POS INIT page. This shows that the ADIRU is ready to accept an inertial position entry. Also, the EICAS memo message ADIRU ALIGN MODE shows.
ADIRU alignment takes between six and fifteen minutes to complete. The time depends on the latitude of the airplane position. If you do not enter a position during this time, the CDU message ENTER INERTIAL POSITION shows.
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To decrease the chance of an initial position entry error, the ADIRU does a position compare test. This test compares the entered inertial position with GPS position or the last stored position if GPS data is not available. The last stored position comes from the nonvolatile memory (NVM) of the ADIRU.
If the ADIRU fails the position compare test, the CDU message ENTER INERTIAL POSITION shows. Enter the new position again to override the position compare test and force the ADIRU to accept the new position.
The ADIRU also does a latitude compare test. This test compares the latitude of the entered position with the ADIRU sensed latitude. If the ADIRU fails the latitude compare test, the CDU message ENTER INERTIAL POSITION shows.
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