VACUUM WASTE SYSTEM -FLUSH CYCLE -FUNCTIONAL DESCRIPTION
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VACUUM WASTE SYSTEM -FUNCTIONAL DESCRIPTION -LAVATORY FLUSH CONTROL
General
There are three lavatory waste systems:
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Waste system one (forward waste tank)
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Waste system two (middle waste tank)
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Waste system three (aft waste tank).
The waste systems have these control circuits:
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Toilet flush/maintenance control
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Vacuum blower control.
There is one toilet flush/maintenance control circuit for each lavatory. A typical circuit shows.
There are two vacuum blower control circuits. Waste system one uses one of the circuits (shown). Waste systems two and three use the other circuit (not shown). The two vacuum blower control circuits are independent.
For the control circuits, these are the most important components and their functions:
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Flush control module (FCM): supplies the control logic for blower and toilet operation
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Tank ball-valve limit switch: prevents blower operation when the valve is open
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Barometric switch: prevents blower operation when airplane altitude is above 16,000 feet (4877 meters)
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Vacuum blower overheat switches: stops the blower if it gets too hot
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The tank logic control module: controls when power goes to the flush control modules (enables/disables toilet flushing).
Toilet Flush/Vacuum Blower Control
When you push the flush switch, the flush control module starts a flush cycle that continues for 15 seconds. The flush control logic sets the sequence of operation for the blower, rinse valve, and the flush valve.
All of these conditions must occur before a flush cycle can start:
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Waste tank: not full
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Point level sensors: one or both serviceable
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Flush switch: push
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Operation power: available, left (right) bus
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Control power: available, left (right) bus or ground handling bus.
All of these conditions must occur before the vacuum blower operates as part of the flush cycle:
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Tank ball valve: closed
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Airplane altitude: below 16,000 feet (4877 meters)
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Vacuum blower motor: no overheat.
If you push the flush switch when a cycle is active, a new cycle will not start. You can only start a new cycle when a flush cycle is complete.
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VACUUM WASTE SYSTEM -FUNCTIONAL DESCRIPTION -LAVATORY FLUSH CONTROL
Toilet Maintenance/Vacuum Blower Control
You use the maintenance switch on the flush control module to cause the flush valve to open. You also use the maintenance switch to operate a vacuum blower for 10 seconds. The flush control module goes back to normal operation when you push the flush switch. The maintenance switch operates when power is available to the flush control module.
Training Information Point
If a vacuum blower motor overheats, make sure the cooling air filter on the blower is clean. A dirty filter can cause the motor to overheat.
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VACUUM WASTE SYSTEM -FUNCTIONAL DESCRIPTION -LAVATORY FLUSH CONTROL
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VACUUM WASTE SYSTEM -TRAINING INFORMATION POINTS -SERVICING
General
Service the lavatory waste tanks through the waste service panel. The panel is located in the aft lower left part of the fuselage, aft of the bulk cargo door. You need a stand to access the panel. The height above the ground changes with airplane weight. Panel height has this range:
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117.4 inches (298.2 cm) minimum
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126.1 inches (320.3 cm) maximum.
The service panel has these components:
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Access door assembly
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Waste drain valve assembly
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Rinse fitting assembly (3)
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T handle (3).
The access door has bumpers that prevent you from closing the door if the service panel is not set for usual operation.
The waste drain valve assembly has these components:
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