12 Questions
What is the primary function of the potable water system?
To supply water for drinking and washing
How is the potable water system pressurized?
By the bleed air system
What is the purpose of the air stop valves in the waste water drain system?
To prevent constant cabin depressurization
How is the waste from the toilet bowl transported?
Under the effect of cabin differential pressure
What generates the necessary delta pressure for the toilet system on the ground and in flight below 16,000 ft?
A vacuum generator
Which system controls the overall toilet system operation, monitoring, and fault indication?
The Vacuum System Controller Function (VSCF)
What is the primary function of the Flush Control Unit (FCU)?
To start the flush sequence and control valve operations
How is the vacuum generator operated at altitudes above 16,000 feet?
The vacuum generator is not started by the VSCF
Where are toilet system fault messages accessible?
Through the Multifunction Control Display Unit (MCDU)
What is the recommended procedure when removing a component from the toilet waste system?
Seal the component in a plastic bag, then attach documents to the sealed bag
Which of the following is NOT a recommended safety precaution when working on the water and waste system?
Work on the waste system and potable water system simultaneously
How should waste fluids be handled during maintenance tasks?
Sort them and use specific waste disposal containers
Study Notes
Toilet System Operation
- The Flush Control Unit (FCU) starts the flush sequence when the flush switch is pressed.
- The FCU opens the rinse valve and flush valve in sequence to evacuate waste material.
- The FCU sends a signal to the VSCF to operate the vacuum generator.
- The vacuum generator creates a differential pressure between the cabin and waste holding tank to move waste from the toilet bowl.
Vacuum System Operation
- Above 16,000 ft, the vacuum generator is not started by the VSCF, as the differential pressure is sufficient.
- The VSCF monitors the operation of the toilet system and sends failure data to the CFDS.
- The CFDS fault messages of the toilet system are accessible via the MCDU.
Safety Precautions
- Obey all AMM safety procedures when working on aircraft to prevent injury and damage.
- Ensure warning notices are in position before starting a task.
- Clean hands with soap and water after completing work to prevent infection.
- Do not work on the waste and portable water systems simultaneously to prevent contamination.
- Use a plastic bag to contain removed components of the toilet waste system and seal the bag before attaching documents.
Potable Water System
- The potable water system supplies water from the water tank to users through a distribution system.
- Users include water faucets in galleys and lavatories, and vacuum toilet units.
- A water heater supplies hot water to the water tap under the washbasin in each toilet unit.
- The potable water system is pressurized by the bleed air system, and optionally by a compressor on the ground.
Waste Water System
- The waste water drain system collects waste water from lavatory washbasins and galley sinks.
- Waste water is discarded outside through the drain valve and heated drain mast.
- Air stop valves avoid constant cabin depressurization by opening only when a certain amount of water is collected.
Waste Holding Tank
- Waste holding tank servicing is done from the toilet servicing panel.
- On ground and in flight below 16,000 ft, a vacuum generator is used to generate the necessary delta pressure.
Learn about the components of an aircraft water and waste system, including the potable water system, waste water system, and toilet system. Understand how water is supplied, distributed, and heated on an aircraft.
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