DOC AIRBUS | AMM A320FPOWER TRANSFER - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The aircraft has a power transfer system to transfer hydraulic power between the Green and Yellow systems. This is necessary if one of the engine pumps fails. It also makes it possible to pressurize the Green system from the Yellow system for maintenance (with the Yellow system electric pump).
The power transfer system is always armed when the hydraulic systems are pressurized. However, the crew can switch it off if necessary.
The connection between the two systems is mechanical. It is impossible for fluid to get from one system to the other.
When the isolation coupling is disconnected (during ground maintenance operations only), there is no transfer of power.
The aircraft has a power transfer system to transfer hydraulic power between the Green and Yellow systems. This is necessary if one of the engine pumps fails. It also makes it possible to pressurize the Green system from the Yellow system for maintenance (with the Yellow system electric pump).
The Power Transfer Unit (PTU) inhibition logic is fully automatic. Manual control or the crew intervention is not necessary.
The connection between the two systems is mechanical. It is impossible for fluid to get from one system to the other.
When the isolation coupling is disconnected (during ground maintenance operations only), there is no transfer of power.
** ON A/C NOT FOR ALL The aircraft has a power transfer system to transfer hydraulic power between the Green and Yellow systems. This is necessary if one of the engine pumps fails. It also makes it possible to pressurize the Green system from the Yellow system for maintenance (with the Yellow system electric pump).
The power transfer system is always armed when the hydraulic systems are pressurized. However, the crew can switch it off if necessary.
The connection between the two systems is mechanical. It is impossible for fluid to get from one system to the other.
When the isolation coupling is disconnected (during ground maintenance operations only), there is no transfer of power.
The aircraft has a power transfer system to transfer hydraulic power between the Green and Yellow systems. This is necessary if one of the engine pumps fails. It also makes it possible to pressurize the Green system from the Yellow system for maintenance (with the Yellow system electric pump).
The Power Transfer Unit (PTU) inhibition logic is fully automatic. Manual control or the crew intervention is not necessary.
The connection between the two systems is mechanical. It is impossible for fluid to get from one system to the other.
When the isolation coupling is disconnected (during ground maintenance operations only), there is no transfer of power.
2. Component Location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 1088GM | PTU | 147 | 29-23-41 | ||
| 3701GM | COUPLING QUICK DISCON | 147 | 27-20-00 | ||
3. System Description
The primary components in the power transfer system are:
** ON A/C NOT FOR ALL The primary components in the power transfer system are:
- the Power Transfer Unit (PTU)
- the Green-System solenoid valve
- the Yellow-System solenoid valve
- the isolation coupling
- the PTU switch.
Power is automatically sensed and transferred through the PTU. A piston in the PTU's control valve is exposed to the Green and Yellow system pressure. When the pressure difference between the Green and Yellow systems is more than 500 psi (34.5 bar), the PTU starts to operate. The PTU transfers power from the system with the larger pressure to the other system. The PTU of the Green and Yellow systems is connected to the Green and Yellow-system solenoid valves.
When the Yellow electric pump starts because of operation of the cargo doors, movement of the flight controls is prevented. Electrical power is supplied to the two solenoid valves of the Green and Yellow systems and the solenoid valve (3160GP) of the Yellow-leakage measurement system. Thus no hydraulic power is supplied to the Green or Yellow system.
The two solenoid valves keep the PTU armed or off. The solenoid valve of the Green system is connected to the Green PTU manifold. The solenoid valve of the Yellow system is connected to the Yellow PTU manifold. The two solenoid valves operate at the same time. The PTU switch on the overhead panel 40VU controls the solenoid valves.
There is no transfer of power when the isolation coupling is disconnected.
The PTU switch is installed in the overhead panel 40VU. All other components are installed in the main landing-gear compartment.
| ------------------------------------------------------------------------------- |
| I MOTOR INLET I PUMP OUTLET I PUMP |
| FLOW DIRECTION I FLOW I FLOW I PRESSURE |
| ------------------------------------------------------------------------------- |
| YELLOW TO GREEN I 119 l/min (31.44 I 95 l/min (25.10 I 206 bar |
| I USgal/min) I USgal/min) I (2987 psi) |
| I (max.) I (max.) I between 20 |
| I I I and 80 l/min |
| I I I (5.28 and 21.13 |
| I I I USgal/min) |
| ------------------------------------------------------------------------------- |
| GREEN TO YELLOW I 76 l/min (20.08 I 55 l/min (14.53 I 206 bar |
| I USgal/min) I USgal/min) I (2987 psi) |
| I (max.) I (max.) I between 13 |
| I I I and 55 l/min |
| I I I (3.43 and 14.53 |
| I I I USgal/min) |
| ------------------------------------------------------------------------------- |
4. Power Supply
The power transfer system gets electrical power from the DC System of the aircraft. The service bus 601PP supplies 28 V DC to the solenoid valves through the PTU switch.
** ON A/C NOT FOR ALL The power transfer system gets electrical power from the DC System of the aircraft. The service bus 601PP supplies 28 V DC to the solenoid valves through the PTU switch.
5. Component Description
A. PTU FIN: 1088-GM
The PTU is made up of a variable displacement unit coupled to a fixed displacement unit. The variable displacement unit is connected to the yellow hydraulic system. The fixed displacement unit is connected to the green hydraulic system. Displacement of the variable displacement unit is varied to maintain the required running and breakdown pressure differentials between systems. Displacement of the variable unit is controlled by means of a control which senses the system delta pressure.
The variable displacement unit is at maximum displacement during the power transfer from the Yellow to the Green system. Then it is at minimum displacement during the power transfer from the Green to the Yellow system.
The variable displacement unit includes a hydraulic servo valve and a variable cam. The servo valve gets input from the pressure differential, which starts the PTU. It controls the displacement of the variable cam which in turn gives the quantity of stroke. During PTU operation, the servo valve controls the pressure differential.
There are three hydraulic connections on the fixed displacement unit and three on the variable displacement unit. The connections are:
The seal drain connection on the PTU is a standard hydraulic union. The high pressure and case drain connections are also standard hydraulic unions. The low pressure connections are self-sealing quick-release couplings.
The PTU is made up of a variable displacement unit coupled to a fixed displacement unit. The variable displacement unit is connected to the yellow hydraulic system. The fixed displacement unit is connected to the green hydraulic system. Displacement of the variable displacement unit is varied to maintain the required running and breakdown pressure differentials between systems. Displacement of the variable unit is controlled by means of a control which senses the system delta pressure.
The variable displacement unit is at maximum displacement during the power transfer from the Yellow to the Green system. Then it is at minimum displacement during the power transfer from the Green to the Yellow system.
The variable displacement unit includes a hydraulic servo valve and a variable cam. The servo valve gets input from the pressure differential, which starts the PTU. It controls the displacement of the variable cam which in turn gives the quantity of stroke. During PTU operation, the servo valve controls the pressure differential.
There are three hydraulic connections on the fixed displacement unit and three on the variable displacement unit. The connections are:
- high pressure,
- low pressure,
- case drain.
The seal drain connection on the PTU is a standard hydraulic union. The high pressure and case drain connections are also standard hydraulic unions. The low pressure connections are self-sealing quick-release couplings.
B. Solenoid Valves
A solenoid-controlled 3/2-way valve is installed in the PTU supply line of each system (Green and Yellow). They operate together to let the PTU operate or not-operate.
When the solenoid valve is energized, the spool moves into the port to close the valve. When the solenoid is de-energized, the spool moves away from the port to open the valve.
A solenoid-controlled 3/2-way valve is installed in the PTU supply line of each system (Green and Yellow). They operate together to let the PTU operate or not-operate.
When the solenoid valve is energized, the spool moves into the port to close the valve. When the solenoid is de-energized, the spool moves away from the port to open the valve.
C. Isolation Coupling 3701GM FIN: 3701-GM
An isolation coupling is installed in the power transfer unit manifold (3015GM) of the Yellow hydraulic system. It is a quick-release coupling which seals automatically when it is disconnected. It also has a ratchet lock to keep it connected.
An isolation coupling is installed in the power transfer unit manifold (3015GM) of the Yellow hydraulic system. It is a quick-release coupling which seals automatically when it is disconnected. It also has a ratchet lock to keep it connected.
D. Pushbutton Switch (P/BSW) 1802GL
The PTU P/BSW 1802GL is on the HYD section of overhead panel 40VU. It lets the crew control the operation of the PTU. The P/BSW is usually set to AUTO. In this position no power goes to the two PTU solenoid valves. If the crew set the P/BSW to OFF, the two solenoid valves get a 28V supply and they close. At the same time, the OFF light in the P/BSW comes on. The P/BSW has a FAULT light which comes on when the hydraulic systems have certain faults.
The PTU P/BSW 1802GL is on the HYD section of overhead panel 40VU. It lets the crew control the operation of the PTU. The P/BSW is usually set to AUTO. In this position no power goes to the two PTU solenoid valves. If the crew set the P/BSW to OFF, the two solenoid valves get a 28V supply and they close. At the same time, the OFF light in the P/BSW comes on. The P/BSW has a FAULT light which comes on when the hydraulic systems have certain faults.
6. Operation/Control and Indicating
A. Usual Flight Condition
The usual flight condition is the PTU system "armed" (the P/BSW set to AUTO and both solenoid valves open) and the Green and Yellow hydraulic systems at the same pressure. Because the pressures of the two hydraulic systems are in 500 psi of each other, the PTU does not operate (transfer pressure).
The usual flight condition is the PTU system "armed" (the P/BSW set to AUTO and both solenoid valves open) and the Green and Yellow hydraulic systems at the same pressure. Because the pressures of the two hydraulic systems are in 500 psi of each other, the PTU does not operate (transfer pressure).
B. Transfer of Power
The PTU automatically starts to operate when the pressure in one of the two hydraulic systems is approximately 500 psi more than the pressure in the other system.
A difference of pressure between the two systems moves the PTU servo valve and the variable cam. This causes a change in the stroke of the variable displacement motor. When the pressure difference is approximately 500 psi the change is enough to make the PTU start. Depending on the direction of movement of the servo valve, the variable displacement unit operates as a pump or as a motor.
If the Green system has less pressure than the Yellow system, the stroke increases to its maximum. The variable displacement (Yellow) unit operates as a motor and the fixed displacement (Green) unit operates as a pump.
If the Yellow system has less pressure than the Green system the stroke decreases to its minimum. The variable and fixed displacement units then operate as a pump and a motor respectively.
The PTU automatically starts to operate when the pressure in one of the two hydraulic systems is approximately 500 psi more than the pressure in the other system.
A difference of pressure between the two systems moves the PTU servo valve and the variable cam. This causes a change in the stroke of the variable displacement motor. When the pressure difference is approximately 500 psi the change is enough to make the PTU start. Depending on the direction of movement of the servo valve, the variable displacement unit operates as a pump or as a motor.
If the Green system has less pressure than the Yellow system, the stroke increases to its maximum. The variable displacement (Yellow) unit operates as a motor and the fixed displacement (Green) unit operates as a pump.
If the Yellow system has less pressure than the Green system the stroke decreases to its minimum. The variable and fixed displacement units then operate as a pump and a motor respectively.
C. Indications and Fault Warnings
Fault Indication on the PTU Pushbutton Switch ** ON A/C NOT FOR ALL
Fault Indication on the PTU Pushbutton Switch ** ON A/C NOT FOR ALL
The PTU status symbols can show on the HYD page of the lower ECAM Display Unit:
The FWC also does a check of the PTU during the start of the engines. When the master switch of the engine 1 (2) is ON and the master switch of the engine 2 (1) is OFF, the PTU cannot operate if:
When the master switches of engine 1 and engine 2 are in the ON position, the PTU can operate. If there is a difference between the Green and Yellow hydraulic systems of more than 650 psi for more than 4 seconds, the ECAM shows a PTU FAULT indication.
Fault Indication on the PTU Pushbutton Switch ** ON A/C NOT FOR ALL Fault Indication on the PTU Pushbutton Switch ** ON A/C NOT FOR ALL The PTU status symbols can show on the HYD page of the lower ECAM Display Unit:
- The PTU status symbols for the Green system are shown in a green color (outline only) during usual operation when the PTU P/BSW is in the AUTO position. The status symbol is not connected to the Green or Yellow system lines. The PTU does not transmit pressure
- The PTU status symbols for the Green system are shown in an amber color (outline only) when there is a PTU fault transmitted from the Flight Warning Computer (FWC) or when the PTU P/BSW is in the OFF position. The status symbol is not connected to the Green or Yellow system lines
- The PTU symbols for the Green system are shown in a solid green color when there is a Green-engine pump low-pressure. The status symbol is connected to the Green and Yellow system lines
- The PTU symbols for the Green system are shown in a solid amber color when there is a Green-engine pump low-pressure together with a PTU fault. The status symbol is connected to the Green and Yellow system lines.
- The PTU symbols for the Yellow system are shown in a solid green color when there is a Yellow-engine pump low-pressure. The status symbol is connected to the Green and Yellow system lines
- The PTU symbols for the Yellow system are shown in a solid amber color when there is a Yellow-engine pump low-pressure together with a PTU fault. The status symbol is connected to the Green and Yellow system lines.
If PTU symbol is not shown on the lower ECAM Display Unit during the operation of the PTU, do the Trouble Shooting of the related system (TSM 29-23-00-02 CONF 00).
NOTE: The PTU status symbol can show when the Green (1074GK) or Yellow (3074GD) engine hydraulic-pump pressure-switch sends a low pressure signal to the ECAM system. In this case, the PTU does not operate and there is no system failure.
The FAULT light of the PTU P/BSW comes on when the sensors in the hydraulic systems detect one of these conditions: - Low fluid contents in the reservoir (Green or Yellow systems)
- Low air pressure in the reservoir (Green or Yellow systems)
- Fluid temperature too high (Green or Yellow systems).
The FWC also does a check of the PTU during the start of the engines. When the master switch of the engine 1 (2) is ON and the master switch of the engine 2 (1) is OFF, the PTU cannot operate if:
- The yellow electric pump is in operation to close the cargo doors
or: - The aircraft is on the ground, only one engine is in operation and the parking brake is ON
or: - The aircraft is on the ground, only one engine is in operation and a towing arm is attached (NWS DISC is ON)
or: - The PTU P/BSW on the panel 40VU is set to OFF.
When the master switches of engine 1 and engine 2 are in the ON position, the PTU can operate. If there is a difference between the Green and Yellow hydraulic systems of more than 650 psi for more than 4 seconds, the ECAM shows a PTU FAULT indication.
D. Aircraft on the Ground
To prevent unwanted operation of the PTU when the aircraft is on the ground, different switches and relays are installed in the aircraft. They operate together to supply power to the two PTU solenoid valves under certain conditions. The PTU will not operate if:
The PTU will operate if:
To prevent unwanted operation of the PTU when the aircraft is on the ground, different switches and relays are installed in the aircraft. They operate together to supply power to the two PTU solenoid valves under certain conditions.
The PTU will not operate if:
The PTU will operate if:
To prevent unwanted operation of the PTU when the aircraft is on the ground, different switches and relays are installed in the aircraft. They operate together to supply power to the two PTU solenoid valves under certain conditions. The PTU will not operate if:
- The Yellow electric pump is in operation to close the cargo doors
or: - The aircraft is on the ground, only one engine is in operation and the parking brake is ON
or: - The aircraft is on the ground, only one engine is in operation, the parking brake is OFF and the nose wheel steering is deactivated
or: - The PTU P/BSW on panel 40VU is set to OFF.
The PTU will operate if:
- The aircraft is on the ground
- Only one engine is in operation
- The NWS DISC is OFF
- The parking brake is OFF
- The PTU P/BSW on the panel 40VU is not set to OFF.
To close the energized solenoid valves a 28 VDC supply is necessary to automatically prevent operation of the PTU. If no supply is available, the isolation coupling prevents operation of the PTU during maintenance.
To prevent unwanted operation of the PTU when the aircraft is on the ground, different switches and relays are installed in the aircraft. They operate together to supply power to the two PTU solenoid valves under certain conditions.
The PTU will not operate if:
- The aircraft is on the ground, the two engines are in operation and the air speed is low (vd<50kts)
or: - The Yellow electric pump is in operation to close the cargo doors
or: - The aircraft is on the ground, only one engine is in operation and the parking brake is ON
or: - The aircraft is on the ground, only one engine is in operation, the parking brake is OFF and the nose wheel steering is deactivated
or: - The PTU P/BSW on panel 40VU is set to OFF.
The PTU will operate if:
- The aircraft is on the ground
- Only one engine is in operation
- The NWS DISC is OFF
- The parking brake is OFF
- The PTU P/BSW on the panel 40VU is not set to OFF.
To close the energized solenoid valves a 28 VDC supply is necessary to automatically prevent operation of the PTU. If no supply is available, the isolation coupling prevents operation of the PTU during maintenance.
E. PTU In-Flight Automatic Inhibition-Logic
The PTU inhibition logic is armed (PTU not inhibited) if:
When the logic is armed, the PTU is inhibited if:
When the PTU is inhibited, this inhibition is cancelled if:
When the logic is armed, the PTU is inhibited if:
When the PTU is inhibited, this inhibition is cancelled if:
The PTU inhibition logic is armed (PTU not inhibited) if:
- The engines 1 and 2 operate (N2>50%) and
- The aircraft is in-flight (NLG not compressed).
When the logic is armed, the PTU is inhibited if:
- The engines 1 and 2 operate (N2>50%) and
- The aircraft is in-flight (NLG not compressed) and
- The Green and/or Yellow hydraulic system(s) is/are in low pressure condition, for a minimum of 6 seconds.
NOTE: The hydraulic system low pressure condition must be sensed with the two of Green (Yellow) system pressure switches installed on the High Pressure manifold (pressure switches 1151GN and 10CE2 for the Green hydraulic system and 3151GN and 10CE3 for the Yellow hydraulic system).
When the PTU is inhibited, this inhibition is cancelled if:
- The N2 of engines 1 and 2 are below 50% or
- The aircraft is on ground (NLG compressed) or
- There is no longer 'low pressure' condition detection, by only one sensor, for a minimum of 20 seconds.
- The aircraft is in-flight (NLG not compressed).
When the logic is armed, the PTU is inhibited if:
- The aircraft is in-flight (NLG not compressed) and
- The Green and/or Yellow hydraulic system(s) is/are in low pressure condition, for a minimum of 6 seconds.
NOTE: The hydraulic system low pressure condition must be sensed with the two of Green (Yellow) system pressure switches installed on the High Pressure manifold (pressure switches 1151GN and 10CE2 for the Green hydraulic system and 3151GN and 10CE3 for the Yellow hydraulic system).
When the PTU is inhibited, this inhibition is cancelled if:
- The aircraft is on ground (NLG compressed) or
- There is no longer 'low pressure' condition detection, by only one sensor, for a minimum of 20 seconds.