DOC AIRBUS | AMM A320FHYDRAULIC FLUID PRESSURE INDICATING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The hydraulic pressure indicating system monitors the hydraulic pressure at different locations in the three hydraulic systems. Two types of detectors are used, pressure switches and pressure transmitters. The data is used for visual on the ECAM display unit and for FAULT action from the ECAM. Discrete signals are also sent to the overhead panel. Some data is sent to other aircraft systems.
** ON A/C NOT FOR ALL The hydraulic pressure indicating system monitors the hydraulic pressure at different locations in the three hydraulic systems. Two types of detectors are used, pressure switches and pressure transmitters. The data is used for visual on the ECAM display unit and for FAULT action from the ECAM. Discrete signals are also sent to the overhead panel. Some data is sent to other aircraft systems.
2. Component Location
** ON A/C NOT FOR ALL 
Component Location| FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 1065GN | HYDR. PRESSURE TRANSMITTER | 147 | 29-32-11 | ||
| 1151GN | SYSTEM-PRESS-SW | 147 | 29-32-12 | ||
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| 2065GN | HYDR. PRESSURE TRANSMITTER | 195BB | 195 | 29-32-11 | |
| ** ON A/C NOT FOR ALL | |||||
| 2065GN | HYDR. PRESSURE TRANSMITTER | 195 | 29-32-11 | ||
| ** ON A/C NOT FOR ALL | |||||
| 2151GN | SYSTEM-PRESS-SW | 195BB | 195 | 29-32-12 | |
| ** ON A/C NOT FOR ALL | |||||
| 2151GN | SYSTEM-PRESS-SW | 195 | 29-32-12 | ||
| ** ON A/C NOT FOR ALL | |||||
| 3065GN | HYDR. PRESSURE TRANSMITTER | 196BB | 196 | 29-32-11 | |
| ** ON A/C NOT FOR ALL | |||||
| 3065GN | HYDR. PRESSURE TRANSMITTER | 196 | 29-32-11 | ||
| ** ON A/C NOT FOR ALL | |||||
| 3151GN | SYSTEM-PRESS-SW | 196BB | 196 | 29-32-12 | |
| ** ON A/C NOT FOR ALL | |||||
| 3151GN | SYSTEM-PRESS-SW | 196 | 29-32-12 | ||
| ** ON A/C ALL | |||||
| 3068GN | HYDR. PRESSURE TRANSMITTER | 198 | 29-32-11 | ||
| 1074GK | ENG-HYD.-PUMP-SW | 435 | 29-11-17 | ||
| ** ON A/C NOT FOR ALL | |||||
| 2074GJ | PRESS SW-ELEC PUMP, B | 195BB | 195 | 29-12-17 | |
| ** ON A/C NOT FOR ALL | |||||
| 2074GJ | PRESS SW-ELEC PUMP, B | 195 | 29-12-17 | ||
| ** ON A/C ALL | |||||
| 3074GD | ENG-HYD.-PUMP-SW | 445 | 29-13-17 | ||
3. System Description
The hydraulic pressure indicating system uses two different types of pressure switch and a single type of pressure transmitter to get system pressure information. The system pressure is monitored:
Type 1 pressure switches are installed downstream of the engine-driven pumps. They monitor the output pressure of the pump.
Type 2 pressure switches are installed downstream of the Blue electric pump and on the three HP manifolds. The first one monitors the output from the Blue electric pump. Those on the HP manifolds monitor the HP of the individual systems downstream of the leakage measurement solenoid valves.
The main difference between the two types of pressure switch is the pressure which they operate at; 1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) for type 1,
1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) for type 2. In addition the type 2 switches give a positive signal when the system is above its low pressure warning threshold. This signal is only used when the switches are installed on the HP manifolds.
The signals from the pressure switches are used to give low pressure indications on the ECAM display unit (through the FWC) and to make the applicable FAULT lights come on (only the switches which monitor pump output operate the FAULT lights). The signals from the pressure switches are also sent to other systems.
One pressure transmitter is installed on each HP manifold. It gives data which is sent to the SDAC. The SDAC uses the data to give the system pressure display on the ECAM.
A fourth transmitter is installed on the brake manifold (Yellow system). The data from this transmitter is sent to the wheel brake system only.
** ON A/C NOT FOR ALL The hydraulic pressure indicating system uses two different types of pressure switch and a single type of pressure transmitter to get system pressure information. The system pressure is monitored:
- downstream of each engine-driven pump (Yellow and Green systems),
- downstream of the electric pump of the Blue system,
- at the HP manifolds (Green, Blue and Yellow systems),
- at the brake manifold (Yellow system).
Type 1 pressure switches are installed downstream of the engine-driven pumps. They monitor the output pressure of the pump.
Type 2 pressure switches are installed downstream of the Blue electric pump and on the three HP manifolds. The first one monitors the output from the Blue electric pump. Those on the HP manifolds monitor the HP of the individual systems downstream of the leakage measurement solenoid valves.
The main difference between the two types of pressure switch is the pressure which they operate at; 1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) for type 1,
1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) for type 2. In addition the type 2 switches give a positive signal when the system is above its low pressure warning threshold. This signal is only used when the switches are installed on the HP manifolds.
The signals from the pressure switches are used to give low pressure indications on the ECAM display unit (through the FWC) and to make the applicable FAULT lights come on (only the switches which monitor pump output operate the FAULT lights). The signals from the pressure switches are also sent to other systems.
One pressure transmitter is installed on each HP manifold. It gives data which is sent to the SDAC. The SDAC uses the data to give the system pressure display on the ECAM.
A fourth transmitter is installed on the brake manifold (Yellow system). The data from this transmitter is sent to the wheel brake system only.
4. Power Supply
The four pressure transmitters must have a 28 V DC supply. The DC busbar 103PP supplies (through circuit breaker 1841GN) the three transmitters which are installed on the HP manifolds. The transmitter which is on the brake manifold gets its 28 V DC supply from the brake system (Ref. AMM D/O 32-00-00-00).
** ON A/C NOT FOR ALL The four pressure transmitters must have a 28 V DC supply. The DC busbar 103PP supplies (through circuit breaker 1841GN) the three transmitters which are installed on the HP manifolds. The transmitter which is on the brake manifold gets its 28 V DC supply from the brake system (Ref. AMM D/O 32-00-00-00).
5. Component Description
A. Pressure Switches FIN: 1151-GN FIN: 2151-GN FIN: 3151-GN
Both types of pressure switch are of the same basic construction. They are cylindrical with a hydraulic connection at one end and an electrical connector receptacle at the other end.
The switch assemblies are made of two main sections, the hydraulic part and the electrical part. The hydraulic part contains a hydraulically-operated piston which moves a diaphragm. The diaphragm forms the seal between the hydraulic and electrical parts of the switch.
The movement of the diaphragm is transferred to a piston which moves a pressure plate. The pressure plate touches a disk spring which is connected to the switch actuator. The switch actuator touches the switching element. The switching element itself is a sub-miniature microswitch.
The switch assembly is made so that a click of the disk spring operates the switching element. Thus, the switch always operates at the same pressure and there is no variation because of contact wear or vibration. The type 1 switch sends a low pressure signal at 1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) pressure decreasing and stops the signal before the pressure is 2200 psi (152 bar) (pressure increasing).
The type 2 switch sends a low pressure signal at 1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) pressure decreasing, and sends a high pressure signal before the pressure is 1750 psi (120 bar) pressure increasing.
The switch assemblies are sealed units and no maintenance is necessary or possible.
Both types of pressure switch are of the same basic construction. They are cylindrical with a hydraulic connection at one end and an electrical connector receptacle at the other end.
The switch assemblies are made of two main sections, the hydraulic part and the electrical part. The hydraulic part contains a hydraulically-operated piston which moves a diaphragm. The diaphragm forms the seal between the hydraulic and electrical parts of the switch.
The movement of the diaphragm is transferred to a piston which moves a pressure plate. The pressure plate touches a disk spring which is connected to the switch actuator. The switch actuator touches the switching element. The switching element itself is a sub-miniature microswitch.
The switch assembly is made so that a click of the disk spring operates the switching element. Thus, the switch always operates at the same pressure and there is no variation because of contact wear or vibration. The type 1 switch sends a low pressure signal at 1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) pressure decreasing and stops the signal before the pressure is 2200 psi (152 bar) (pressure increasing).
The type 2 switch sends a low pressure signal at 1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) pressure decreasing, and sends a high pressure signal before the pressure is 1750 psi (120 bar) pressure increasing.
NOTE: When the type 2 switch is installed to monitor system pressure, it gives a signal at both low and high pressures.
The two types of switches have different electrical connectors and also hydraulic connections of different dimensions. The switch assemblies are sealed units and no maintenance is necessary or possible.
B. Hydraulic Pressure Transmitter (1065GN, 2065GN, 3065GN, 3068GN)
The four pressure transmitters are of the same type. They are cylindrical with a hydraulic connection at one end and an electrical connector receptacle at the other end.
The transmitters are made of two main sections. The first section has the pressure-sensing element. It includes a diaphragm which is under hydraulic pressure. The diaphragm causes a piezoresistive sensing element to operate on the Wheatstone bridge principle, according to the pressure applied.
The other section of the transmitter contains two circuit boards. The circuit boards have circuits which control the input voltage and increase the strength of the output signal from the switching element.
The specified input voltage is 28 V DC, but the transmitter will operate satisfactorily between 18 and 32 V DC.
The output voltage varies linearly from 1 V DC for 0 bar (0 psi) to 5 V DC for 200 bar (2900 psi).
The transmitters are sealed units and no maintenance is necessary or possible.
The four pressure transmitters are of the same type. They are cylindrical with a hydraulic connection at one end and an electrical connector receptacle at the other end.
The transmitters are made of two main sections. The first section has the pressure-sensing element. It includes a diaphragm which is under hydraulic pressure. The diaphragm causes a piezoresistive sensing element to operate on the Wheatstone bridge principle, according to the pressure applied.
The other section of the transmitter contains two circuit boards. The circuit boards have circuits which control the input voltage and increase the strength of the output signal from the switching element.
The specified input voltage is 28 V DC, but the transmitter will operate satisfactorily between 18 and 32 V DC.
The output voltage varies linearly from 1 V DC for 0 bar (0 psi) to 5 V DC for 200 bar (2900 psi).
The transmitters are sealed units and no maintenance is necessary or possible.
6. Operation/Control and Indicating
A. Pump Output Monitor
The pressure switches (1074GK, 2074GJ and 3074GD) downstream of the engine pumps and downstream of the Blue electric pump monitor the output of the pumps. When the pressure falls below a specified pressure,
1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) for the engine pumps
(1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) for the Blue electric pump), the switch contacts close and complete the circuits. A signal is sent to the SDAC which gives these warnings:
At the same time a signal is sent to the overhead panel 40VU and the applicable FAULT legends come on.
The pressure switches (1074GK, 2074GJ and 3074GD) downstream of the engine pumps and downstream of the Blue electric pump monitor the output of the pumps. When the pressure falls below a specified pressure,
1740 + 72.5 - 72.5 psi (120 + 5 - 5 bar) for the engine pumps
(1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar) for the Blue electric pump), the switch contacts close and complete the circuits. A signal is sent to the SDAC which gives these warnings:
- the pump low pressure warning on the HYD page of the system display of the ECAM,
- the applicable text on the engine/warning display of the EACM,
- the single-chime audio warning,
- the MASTER CAUT warning light comes on.
At the same time a signal is sent to the overhead panel 40VU and the applicable FAULT legends come on.
B. System Pressure Monitor
The pressure switches (1151GN, 2151GN, 3151GN) on the HP manifolds of the three systems monitor the pressure in the systems. When the pressure is above the low pressure warning threshold 1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar), the switch sends a signal to the flight control system. The Green and Yellow system switches also send signals to the autoflight system. The Green system switch also sends a signal to the brake system.
When the pressure in the system falls below 1450 + 72.5 - 72.5 psi
(100 + 5 - 5 bar), the pressure switch operates and stops the signals to the flight controls (and autoflight/brake systems). At the same time the switch sends a signal to the FWC which gives these warnings:
The pressure switches (1151GN, 2151GN, 3151GN) on the HP manifolds of the three systems monitor the pressure in the systems. When the pressure is above the low pressure warning threshold 1450 + 72.5 - 72.5 psi (100 + 5 - 5 bar), the switch sends a signal to the flight control system. The Green and Yellow system switches also send signals to the autoflight system. The Green system switch also sends a signal to the brake system.
When the pressure in the system falls below 1450 + 72.5 - 72.5 psi
(100 + 5 - 5 bar), the pressure switch operates and stops the signals to the flight controls (and autoflight/brake systems). At the same time the switch sends a signal to the FWC which gives these warnings:
- the single-chime audio warning,
- the MASTER CAUT warning light comes on,
- the system label on the ECAM system display changes color to amber,
- the applicable text on the engine/warning display of the ECAM.
When the pressure in the system increases again to 1750 psi (121 bar), the pressure switch sends a signal to the FWC which cancels these warnings: - the single-chime audio warning,
- the MASTER CAUT warning light,
- the applicable text on the engine/warning display of the ECAM,
- the system label on the ECAM system display changes color from amber to white,
- the arrow below the system label on the ECAM system display changes color from amber to green.
C. System Pressure Indication
The three pressure transmitters (1065GN, 2065GN, 3065GN) measure the pressure in each system and send signals to the SDAC. The SDAC uses the data to give a digital display of the actual system pressure (with a resolution of 50 psi) on the ECAM display unit.
If the pressure falls to below 1450 psi (100 bar), the SDAC changes the color of the digital display from green to amber.
These three transmitters also send information to the flight control system.
The pressure transmitter 3068GN is for the brake system and only supplies that system with data.
The three pressure transmitters (1065GN, 2065GN, 3065GN) measure the pressure in each system and send signals to the SDAC. The SDAC uses the data to give a digital display of the actual system pressure (with a resolution of 50 psi) on the ECAM display unit.
If the pressure falls to below 1450 psi (100 bar), the SDAC changes the color of the digital display from green to amber.
These three transmitters also send information to the flight control system.
The pressure transmitter 3068GN is for the brake system and only supplies that system with data.