Hydraulics Flashcards
What is the operating pressure of the hydraulic systems?
3000psi
What are the possible pressure sources for the hydraulic systems?
Engine Driven Pumps
Electric Pumps
Ram Air Turbine (RAT)
Power Transfer Unit (PTU)
How is the system pressurized?
By bleed air from Engine 1 or through the cross bleed duct.
What powers the Green System?
Engine 1 hydraulic pump
What does the Power Transfer Unit (PTU) do?
Compares the Yellow and Green systems and pressurizes the lower with the higher if the differential is >500psi.
What backup system does the yellow system have that the green does not?
A backup electric pump and hand pump.
What does the yellow system power?
Flaps
NWS
ALT/PARK Brakes
Cargo doors
Thrust Reverser #2
Various flight controls
How is the BLUE system powered?
Electric pump ONLY
PTU can not pressurize
There are no engine pumps
RAT
During engine failure or fire, the hydraulic valve closes on the ECAM. What is unique about the Yellow and Green systems when the valve is closed?
Although not depicted, the electric (yellow) or PTU can still pressurize the system without the engine operating.
When is the PTU monitored and what does an amber indication mean?
The PTU is only tested during second engine startup. It is not monitored at any other time.
The amber PTU line on the ECAM means that the PTU has been selected OFF.
What happens when the cargo doors are operated with the engines off?
The yellow electric pump engages when the cargo door is operated.
When will the RAT deploy?
When power is lost to both AC BUS 1 & 2.
When is the hydraulic pressure displayed in amber?
<1450psi
Beside a pump failure, why else would you see a FAULT light on the hyd system?
Reservoir overheat
Reservoir low air pressure
Low Fluid Level
Why would you manually deploy the RAT?
To pressurize the system without activating the emergency generator.
Only required if electric pump is lost and one of the other hyd systems has also failed.
Name the 3 ways the RAT will be deployed?
Auto with loss of AC BUS 1&2
RAT MAN ON pb (no emer gen)
MAN ON on EMER ELEC PWR1
What does it mean when you have all FAULT lights on during pre-flight?
The pneumatic reservoir pressure has bled overnight. APU bleed air will re-pressurize and extinguish the FAULTs
When is the PTU inhibited?
Split Engine Master Switches
\+
Nosewheel disconnected or Parking brake ON
\+
On the ground
OR
40 seconds after cargo door operation
Why should you delay second engine start 1 minute after cargo door ops?
The PTU is inhibited 40 seconds after cargo door ops to prevent inadvertent pressurizing the green side. When inhibited, the PTU will fail its self-test after 2nd engine start.
What are the 3 types of reservoir problems?
Low Fluid Level
Low Air Pressure
Overheat
What is the function of the system accumulators?
An accumulator in each system helps to maintain a constant pressure by covering transient demands during normal operation.
When does the RAT extend automatically?
The RAT extends automatically if AC BUS 1 and AC BUS 2 are lost.
What is the normal pressure in the hydraulic system?
3000psi.
What is the function of the fire shutoff valves?
Each of the green and yellow system has a fire shutoff valve in its line upstream of its engine-driven-pump. The flight crew can close it by pushing the ENG1(2) FIRE pb.
How many hydraulic systems has the A321?
The aircraft has three hydraulic systems referred to as GREEN BLUE and YELLOW.
During start up when is the BLUE hydraulic system pressurized?
Automatically after first engine start.
What does the RAT MAN ON switch do?
Extends RAT pressurizes BLUE system does not start Emergency Generator.
What is the function of the Power Transfer Unit (PTU)?
The bidirectional PTU enables the yellow system to pressurize the green system and vice versa.
You get a G RSVR OVHT message. Why does the ECAM procedure ask you to switch off the PTU first?
To prevent the PTU from pressurizing the GREEN system.
Can you transfer hydraulic fluid between the hydraulic systems?
No hydraulic fluid cannot be transferred from one system to another.
