AIR/GROUND SYSTEM -WOW CARDS AND AIR/GROUND RELAYS
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AIR/GROUND SYSTEM -FUNCTIONAL DESCRIPTION
Power Supply
The systems cardfiles supply 28v dc electrical power to the WOW cards. The left WOW card gets power from battery bus section 2 and the hot battery bus. The right WOW card gets power from the right main bus and the hot battery bus.
The left, right, or battery buses supply 28V dc electrical power to the air/ground relays in the ELMS.
Load Sensors
The weight of the airplane on the ground causes the main landing gear beams to bend. Two load sensors on each main landing gear beam measure this bending and send analog signals to the WOW cards.
WOW Cards
Each WOW card supplies power to and gets input from a load sensor on each of the main landing gear beams.
The WOW cards send air/ground data to airplane systems through the ASG cards and the systems ARINC 629 buses.
The WOW cards also control the air/ground relays in the ELMS.
Air/Ground Relays
The right WOW card controls master air mode and ground mode relays in the P210 and P310 power management panels.
EFFECTIVITY
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The left WOW card controls master air mode and ground mode relays in the P110 power management panel.
The WOW cards supply the ground to energize the master relays.
The master relays supply the ground to the slave relays. The slave relays supply the air/ground output to the airplane systems.
Training Information Point
The WOW cards energize the air mode relays in the air and energize the ground mode relays on the ground.
When a relay fails, it almost always fails to the de-energized position.
The de-energized position for the air mode relays is the ground state. The air mode relays are also called fail-to-ground relays.
The de-energized position for the ground mode relays is the air state. The ground mode relays are also called fail-to-air relays.
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AIR/GROUND SYSTEM -FUNCTIONAL DESCRIPTION
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AIR/GROUND SYSTEM -INDICATION
Maintenance Page
The air or ground output from each of the load sensors shows on the landing gear actuation/indication maintenance page. This page shows simulated air or ground conditions with the word SIM next to the AIR or GND indication.
Status Display
Status messages show if there is a fault in either the left or the right air/ground system.
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777 AIRCRAFT MAINTENANCE MANUAL
AIR/GROUND SYSTEM -INDICATION
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AIR/GROUND SYSTEM -SYSTEM TESTS
General
These are the air/ground system tests:
*
LEFT AIR/GROUND SYSTEM
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LEFT MLG BEAM -(LEFT SYS) CALIBRATION, M32101
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LEFT MLG BEAM -(RIGHT SYS) CALIBRATION, M32201
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RIGHT AIR/GROUND SYSTEM
*
RIGHT MLG BEAM -(LEFT SYS) CALIBRATION, M32102
*
RIGHT MLG BEAM -(RIGHT SYS) CALIBRATION, M32202.
Air/Ground System Tests
There is an air/ground test for each of the air/ground systems. These tests do a check of the functions of the air/ground system components.
Load Sensor Calibration
After you replace a load sensor, you must calibrate the sensor. There is a calibration function for each of the four sensors. If you replace the two WOW cards, you must calibrate all four of the load sensors.
The calibration function permits you to calibrate the sensor to the ground mode or to the air mode.
If the airplane is on the landing gear, ground calibration should be done. If the airplane is on jacks, air calibration should be done.
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777 AIRCRAFT MAINTENANCE MANUAL
AIR/GROUND SYSTEM -SYSTEM TESTS
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AIR/GROUND SYSTEM -SPECIAL FUNCTIONS
General
You can control air mode and ground mode simulation through these six special functions on the MAT:
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Left air simulation
*
left ground simulation
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Left stop simulation
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Right air simulation
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Right ground simulation
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