QUANTITY INDICATING - DESCRIPTION AND OPERATION

** ON A/C NOT FOR ALL

1. General
The quantity indicating system gives an indication of water quantity available in the potable water tank. The indicating system is installed to help the ground and cabin service personnel.
The quantity indicating system gives an indication of water quantity available in the potable water tank. The indicating system is installed to help the ground and cabin service personnel. A pre-selection system is installed on the Flight Attendant Panel (FAP).
The quantity indicating system gives an indication of water quantity available in the potable water tank. The indicating system is installed to help the ground and cabin service personnel.
The indication display on the Flight Attendant Panel (FAP) is a part of the CIDS system (Ref. AMM D/O 23-73-00-00).

** ON A/C NOT FOR ALL

2. Component Location

Quantity Indication System - Component Location ** ON A/C NOT FOR ALL

Quantity Indicating System - Component Location ** ON A/C NOT FOR ALL

Quantity Indication System - Component Location ** ON A/C NOT FOR ALL

Quantity Indicating System - Component Location. ** ON A/C NOT FOR ALL

Quantity Indication System - Component Location ** ON A/C NOT FOR ALL

Quantity Indicating System - Component Location. ** ON A/C NOT FOR ALL

FIN	FUNCTIONAL DESIGNATION	PANEL	ZONE	ATA REF
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3MA	TRANSMITTER,QUANTITY	161DW	171	38-13-11
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3MP	LIM SW-DRAIN HANDLE		171	38-14-17
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3MA	TRANSMITTER,QUANTITY		137	38-13-11
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3MA	TRANSMITTER,QUANTITY		171	38-13-11
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5MA	MSW-LIMIT SW		171	38-13-16
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6MA	INDICATOR,QUANTITY		171	38-13-21
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10MA	IND-FULL	2023VU	171	38-11-00
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10MA	IND-FULL 1		171	38-11-00
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300RH7	DECODER/ENCODER UNIT B		263	23-31-00
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300RH7	DECODER/ENCODER UNIT B		243	23-31-00

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3. Description

Water Quantity Transmitter 3MA ** ON A/C NOT FOR ALL

A. Water Quantity Transmitter 3MA
Water quantity transmitter 3MA is installed in the water tank and monitors the volume of remaining water in the tank.

B. Service Door 171AL
Service door 171AL operates micro switch 5MA. The micro switch controls the power supply to the quantity indicating system.

C. Quantity Indicating Water Tank

(1) Light Emitting Diode (LED)
The Light Emitting Diode (LED) indicator on the forward attendant panel shows the contents of the water tank in percentage.

(2) The FAP Quantity Indicator:

The indicator on the FAP shows the contents of the water tank in percentage.

D. Circuit Breaker 1MA
Circuit breaker 1MA gives electrical protection to the quantity indicating-system circuit.

E. Tank Full Indicator-Light (10MA)
Tank full indicator-light (10MA) on the potable-water service panel will come on when the water tank is full and the fill/drain valve is closed.
Tank full indicator-light (10MA) on the potable-water service panel will come on when the water in the tank gets the pre-selected quantity and the fill/drain valve is closed.

F. Pre-selection
The pre-selection module is installed on the FAP. The pre-selection system gets its information from the DEU B, the DIR 2 and the DIR 1. The potable water system is connected to the CIDS (Ref. AMM D/O 23-73-00-00).
The total water quantity is shown on the FAP in liters and in US gallons.
A tank symbol with an arrow and scale shows the water quantity and the selected value.
A pop-up window with the identification 'SELECTED QUANTITY' let you set the necessary pre-selected water quantity.

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4. System Operation

Quantity Indicating System - Electrical Schematic ** ON A/C NOT FOR ALL

Quantity transmitter 3MA operates as a variable capacitor and uses the water in the tank as the variable component. Any increase of water in the tank increases the output signal, decrease of water in the tank decreases the output signal.
Two quantity indicators are supplied with transmitter output signal. The signal to service panel indicator 6MA moves a pointer over a scale calibrated in increments of volume. The signal to the FAP LED indicator shows the percentage of volume if the panel pushbutton switch is pushed or the potable-water service panel is open.
The FULL indication light on the service panel will come on when the tank is full.
The quantity indicator on the FAP gets its information from the potable water system-transmitter.
The signal to the FAP quantity indicator shows the percentage of volume.
When you push the Water/Waste key on the FAP, the WATER/WASTE page comes into view and the potable water and waste quantity comes into view. The value of water quantity is shown on the WATER QUANTITY display.
System information of the potable water system is shown on the MESSAGE Screen when the system info key is pushed.
The FULL indication light on the service panel comes on when the tank is full.
Quantity indicator 6MA on the service panel shows the contents of potable water in the potable water tank.
A rectangle box with the message 'NO WATER PRESSURE' is shown (on the aircraft symbol) if there is no water pressure available in the potable water system.
If there is no water in the potable water system:

The symbol of the potable water tank has a blue card with the message 'NO WATER QUANTITY DATA AVAILABLE' on it.

The quantity indicator on the FAP gets its information from the potable water system-transmitter.
The signal to the FAP quantity indicator shows the percentage of volume.
When you push the Water/Waste key on the FAP, the WATER/WASTE page comes into view and the potable and waste quantity comes into view. The value water quantity is shown on the WATER QUANTITY display.
System information of the potable water system is shown on the MESSAGE Screen when the System info key is pushed.
The FULL indication light on the service panel comes on when the tank is full.
Quantity indicator 6MA on the service panel shows the contents of potable water in the potable water tank.
A rectangle box with the message 'NO WATER PRESSURE' is shown (on the aircraft symbol) if there is no water pressure available in the potable water system.
Pre-selection:
The pre-selection is entered in 25% steps only and is shown on the scale where you select the necessary quantity.
If there is no water in the potable water system:

The symbol of the potable water tank has a blue card with the message 'NO WATER QUANTITY DATA AVAILABLE' on it.

The transmitter also has a low-level switch which opens when the water tank contents decrease to a set level. When the low-level switch opens, it disconnects the electrical supply to the water heaters in the lavatories.
The transmitter also has a high-level switch which controls the operation of a relay to close fill/overflow drain valve 16MA. The high level switch will de-energize the relay to stop the filling procedure when the tank is full.
The transmitter also has a high-level switch which controls the operation of a relay to close fill/overflow drain valve 8MA. The high level switch will de-energize the relay to stop the filling procedure when the tank is full.
Micro switch 5MA closes to energize the indicating system when service door 171AL is open for ground servicing. Micro switch 5MA isolates the indicating system when service door 171AL is closed again.
A membrane switch identified with 'IND ON', is installed on the forward attendant panel. The membrane switch overrides micro switch 5MA, if you push it.
A rectangle box with the message 'NO WATER PRESSURE' is shown (on the aircraft symbol) if there is no water pressure available in the potable water system.
If there is no water in the potable water system:

The symbol of the potable water tank has a blue card with the message 'NO WATER QUANTITY DATA AVAILABLE' on it.
If there is no potable water information available:
The blue card with the message 'NO WATER QUANTITY DATA AVAILABLE', and
A blue card with the message 'NO WATER PRESELECT AVAILABLE' come into view.

A rectangle box with the message 'NO WATER PRESSURE' is shown (on the aircraft symbol) if there is no water pressure available in the potable water system.
If there is no water in the potable water system:

The symbol of the potable water tank has a blue card with the message 'NO WATER QUANTITY DATA AVAILABLE' on it.

If there is no potable water information available:

The blue card with the message 'NO WATER QUANTITY DATA AVAILABLE' comes into view.

When you push the pre-selection key 'Pre-Select', a pop-up window with the indication SELECTED QUANTITY comes into view. You can now select the necessary water quantity. The pre-selection value starts at 25% and continues to 12.5% at each step. The window has two push keys, one with (+) to increase the pre-selection value and one with (-) to decrease it.
When the water quantity is at the pre-selected value, quantity transmitter 3MA sends a signal to pre-selection control unit 7MA. The pre-selection control unit then sends a signal to close fill/overflow and drain valve 8MA.

[Rev.10 from 2021] 2026.04.02 06:51:31 UTC