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?
2 Thrust Reverser
Brakes
Cargo doors
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
An accumulator in each system helps to maintain a constant pressure by covering transient demands during normal operation.
What is the function of the system accumulators?
The RAT extends automatically if AC BUS 1 and AC BUS 2 are lost.
When does the RAT extend automatically?
3000psi.
What is the normal pressure in the hydraulic system?
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.
What is the function of the fire shutoff valves?
The aircraft has three hydraulic systems referred to as GREEN BLUE and YELLOW.
How many hydraulic systems has the A320?
Automatically after first engine start.
During start up when is the BLUE hydraulic system pressurized?
Extends RAT pressurizes BLUE system does not start Emergency Generator.
What does the RAT MAN ON switch do?
The bidirectional PTU enables the yellow system to pressurize the green system and vice versa.
What is the function of the Power Transfer Unit (PTU)?
To prevent the PTU from pressurizing the GREEN system.
You get a G RSVR OVHT message. Why does the ECAM procedure ask you to switch off the PTU first?
No hydraulic fluid cannot be transferred from one system to another.
Can you transfer hydraulic fluid between the hydraulic systems?
> 500psi.
The PTU start running if the differential pressure between the green and yellow hydaulic system is …
Each hydraulic system has a leak measurement valve upstream of the primary flight controls. These valves which measure the leakage in each circuit are closed by operation of the LEAK MEASUREMENT VALVES pushbutton switch on the maintenance panel.
What is the purpose of the leak measurement valves?
Normally HP bleed air from engine 1 pressurizes the hydraulic reservoirs automatically to maintain a high enough pressure to prevent their pumps from caviating.
Why are the hydraulic reservoirs pressurized with bleed air?
A drop-out RAT coupled to a hydraulic pump allows the blue system to function if electrical power is lost or both engines fail. The RAT deploys automatically if AC BUS 1 and AC BUS 2 are lost and It can be deployed manually from the overhead panel. It can be stowed only when the aircraft is on the ground.
What is the purpose of the RAM AIR TURBINE (RAT)?
Four elec pump engine pump PTU and hand pump.
How many pumps are located within the YELLOW system?
The warning level.
What does the amber level indication mean on the hydraulic quantity indicator?
Priority valves cut off hydraulic power to heavy load users if hydraulic pressure in a system gets low.
What is the function of the priority valves?
On:Pump is on when the engine is running.OFF:The pump is depressurized.FAULT Light:With ECAM caution if:- Reservoir low level- Reservoir overheat (stays on while condition lasts)- Reservoir low air pressure- Low pump pressure (inhibited on the ground, when the engine is stopped)
ENG 1 (2) PUMP pb (HYD Panel)
- ON
- OFF
- FAULT Light
AUTO:If AC power is available, the electric pump operates:- In flight- On the ground, if one engine is running.OFF:The pump is de-energized.FAULT Light:With ECAM caution if:- Reservoir low level- Reservoir low air pressure- Reservoir overheat (stays on while condition lasts)- Pump low pressure (inhibited on the ground, when the engines are stopped)- Pump overheat
BLUE ELEC PUMP pb
(HYD Panel)
- AUTO
- OFF
- FAULT Light
(springloaded)ON:Electric pump is ON. If the electrical power supply is removed, the pump remains off when electrical power is applied again.Off:The pump is off. It comes on automatically during cargo door operation. This inhibits the operation of other yellow system functions (except alternate braking and engine 2 reverse).FAULT Light:With ECAM caution if:- Reservoir low level- Reservoir low air pressure- Reservoir overheat (stays on while condition lasts)- Pump low pressure- Pump overheat
YELLOW ELEC PUMP pb
(HYD Panel)
- ON
- OFF
- FAULT Light
AUTO:The power transfer unit is armed and both the Y and G electrohydraulic valves are open. PTU runs automatically when the differential pressure between the green and yellow systems is > 500 PSI.Inhibited:- during the first engine start, (split MASTER SW + parking break or NWS disconnected)- during cargo door operation, and after that for 40 secAutomatically tested during the second engine start.OFF:Both the green and the yellow PTU electrohydraulic valves close. Powertransfer stops.FAULT Light:With ECAM caution if:- G or Y reservoir low air pressure- G or Y reservoir low level- G or Y reservoir overheat(stays on as long as the overheat lasts).
PTU pb
(HYD Panel)
- AUTO
- OFF
- FAULT Light
The flight crew may extend the RAT at any time by pressing the RAT MAN ON pb.
RAT MAN ON pb
HYD Panel
- Landing Gear- Normal Brakes- Slats/Flaps- Engine 1 Reverser
Name several items that run from only the GREEN system?
Hydraulic power to the flaps, slats, landing gear, NWS, and emergency generator is cut off if the pressure drops below a predetermined value (High demand items)
What is the function of they hydraulic priority valves?
Yellow
What hydraulic system supplies nose wheel steering?
With the Yellow hydraulic system electric pump
When brake accumulator pressure is low, how is it recharged?
Yes, at 1/2 speed
With only Green hydraulic system pressure available, will both the flaps and slats operate?
No, the THS requires hydraulic power from the Green or Yellow systems
If NO hydraulic power is available can the THS be positioned?
- Normal Brakes: GREEN- Alternate Brakes: YELLOW backed up by a hydraulic accumulator
Which hydraulic systems provide pressure to the brakes?
No, not with the alternate brake system
If you lose Green hydraulic pressure, will you have auto brakes?
- Yellow hydraulic pressure delivered to the left and right brakes- Yellow system brake accumulator pressure
What does the BRAKES & ACCU PRESS triple indicator indicate?
Press the brake pedals to ensure the aircraft slows, and check the brake pressure on the triple indicator is zero, indicating the Green hydraulic system has taken over
How do you perform the brake check during initial taxi?
No, you must have at least one
Can the aircraft be flown with a loss of all hydraulic systems?
The RAT extends providing pressure to the BLUE hydraulic pump
What occurs when you pres the RAT MAN ON pushbutton?
No
Does the PTU transfer hydraulic fluid?
- 1 Engine driven pump- 1 PTU
How many hydraulic pumps are in the GREEN system?
- 1 Electric pump- 1 RAT
How many hydraulic pumps are in the BLUE system?
- 1 Engine driven pump- 1 Electric pump- 1 PTU- 1 Hand Pump
How many hydraulic pumps are in the YELLOW system?
3000 psi +/-200
What is normal system hydraulic pressure?
No, it must be deployed manually by the RAT MAN ON pushbutton
Does the RAT automatically deploy with the loss of BLUE hydraulic pressure?
A difference of 500 psi between the GREEN and YELLOW hydraulic systems
What condition will cause the PTU to operate when the pushbutton is in AUTO?
To provide Yellow hydraulic pressure for cargo door operation
What is the purpose of the hand pump?
8 seconds (3 seconds for rat to extend, and 5 seconds to pressurize the Blue hydraulic system and power the EMER GEN)
How long does it take for the RAT to extend and provide power?
- PTU pushbutton is OFF- First Engine start- Parking brake is ON and only one ENG MASTER switch is ON- NWS in towing position and parking brake ON- Cargo door operation (PTU is also inhibited for 40 seconds after the end of cargo door operation)
When is the PTU inhibited?
- NWS- Alternate Brakes- Parking Brake- Cargo Doors- Engine 2 Reverser
Name several items that run from only the YELLOW system?
Obtain ground clearance then turn ON the YELLOW ELEC PUMP to pressurize the accumulator
If the ACCU PRESS indicator is low, what should you do?
No, it is inhibited
Does operating the cargo door run the PTU?
- Alternate Braking- Engine 2 reverser- NWS (if bypass pin not installed)
Which systems are not inhibited during cargo door operation?
- After the first engine is started- If the BLUE PUMP OVRD pb on the MX Panel has been pressed with no engine running
When does the BLUE ELEC PUMP operate?
Yes, FAULT light illuminated in the respective ENG PUMP pushbutton
If the “FAULT” light in the PTU pushbutton is ON, are there any other indications on the HYD Panel?
No, not until the overheat condition subsides
If the ECAM actions lead you to turn OFF the PTU for a Reservoir Overheat, will the FAULT light go out?
Yes
Can the YELLOW ELEC PUMP run the PTU?
- Overtemp in Reservoir- Low air pressure in the reservoir- Low quantity in the reservoir
What does an amber “FAULT” light in the PTU pushbutton indicate?
- Pump pressure low- Overtemp in the reservoir- Low air pressure in the reservoir- Low quantity in the reservoir- Overheat of pump
What does a “FAULT” light in the BLUE or YELLOW ELEC PUMP pushbutton indicate?
Blue HYD pressure only, no emergency generator
What is different about the deployment of the RAT from the HYD panel?