Hydraulic Power System Component Location Airbus320


On the green system the normal source of pressure is the Engine Driven
Pump (EDP) and as auxiliary source the Power Transfer Unit (PTU).
On the blue system the normal source of pressure is the electrical pump
(E-Pump) and as auxiliary source the Ram Air Turbine (RAT).
NOTE: The blue electric pump can be used as an auxiliary power source
for maintenance purposes on ground.
On the yellow system the normal source of pressure is the EDP and as
auxiliary sources the PTU and the electric pump (E- Pump).
NOTE: The yellow system also has a hand pump dedicated to cargo
door operation.
The PTU is an auxiliary pressure supply for either the green or yellow
systems without transfer of fluid between the two systems.
It operates automatically if there is a delta pressure of 500psi between
the green / yellow or yellow / green hydraulic systems.
The side operating as a pump will take fluid from its associated
reservoir and provide an output through the PTU manifold to the HP
The motor side is supplied from the HP manifold through the PTU
manifold, and is connected to the return system. The PTU is
de-activated by closing the solenoid valves on the PTU manifolds.
Each section of the PTU has a case drain connection to the return
The RAT is an auxiliary pressure supply for the blue system, and for
the emergency electrical power Constant Speed Motor/Generator
(CSM / G). It can be deployed automatically or manually depending
on the failure conditions. The RAT is locked when extended.

An interlock mechanism will only permit RAT stowage if the blades
are properly aligned.
It also prevents rotation when stowed. The interlock will release at
approximately 5 degrees from the full extension position.
Extension is by spring force. Retraction (stowage) is by blue hydraulic
Up lock release is by solenoid operation.
Down lock release is by hydraulic pressure

The PTU is located in the main landing gear bay. The blue electric
pump and the RAT are located in the blue hydraulic bay and the yellow
electric pump is located in the yellow hydraulic bay.

The EDPs 1 and 2 are located on the accessory gearbox of engine 1
(EDP 1 green system) and engine 2 (EDP 2 yellow system).
The green reservoir is located inside the main landing gear bay. The
blue reservoir is located aft of the main landing gear bay on the LH
side. The yellow reservoir is located inside the yellow hydraulic bay.

The hydraulic servicing panels are located aft of the main landing
gear bay; the green and the blue panels on the LH side, and the yellow
panel on the RH side.

The three independent hydraulic systems respectively supply the users
indicated on the diagram. Between these systems, the users are shared in
order to ensure the aircraft control, even if only one hydraulic system is
inoperative. On the blue hydraulic system, the Constant Speed
Motor/Generator (CSM/G) is used to provide aircraft electrical power in
case of emergency.
In the event of low hydraulic pressure, the priority valves maintain the
operation of essential systems by cutting off hydraulic power to heavy
load users.

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