Hydraulics Flashcards
Hydraulics
How many hydraulic systems are there ?
3
Left, right and center.
Hydraulics
What are the differences between the left and the right hydraulic systems ?
None !
They are identical.
Hydraulics
Which hydraulic system powers the landing gear actuation ?
The center hydraulic system.
Hydraulics
Which hydraulic system powers the nose gear steering ?
The center hydraulic system.
Hydraulics
What triggers a Hydraulic pump FAULT light ?
- Low pump pressure
- High pump fluid temperature
- Pump is selected OFF
Hydraulics
What is the Hydraulic operating pressure ?
5000 psi
Hydraulics
Under which conditions do the electric L and R demand pumps operate when in AUTO position ?
- LOW system pressure.
- For 3 minutes after both ENG start on the ground.
- From T-OFF thrust set to flaps retraction.
- From gear down or RA < 1000 ft to GS < 40 kts
- During thrust REV operations
Hydraulics
How many pumps does the center Hydraulic system have and how are they driven ?
2 electric motor driven pumps (EMPs)
Hydraulics
Which Center system pump operates as Primary ? Which as Demand ?
The FMC (Flight Management Computer) determines which pump operates as Primary based on calendar days :
C1 is primary on odd days
C2 is primary on even days
Hydraulics
When does the Center PRIMARY pump operate ?
Continuously after the second engine is started.
Hydraulics
When does the Center DEMAND pump operate ?
- LOW system pressure
- For 3 minutes immediately after both engines have been started.
- From T-OFF thrust set to RA > 2000 ft
- Flaps or slats in motion.
- During descent when landing gear down and RA < 2000 ft until GS < 60 kts.
Hydraulics
What does the RAT provide when deployed ?
It provides hydraulic power to the primary flight control components connected to the center hydraulic system.
Hydraulics
What does the UNLKD light indicate on the RAT switch ?
The RAT is not in the stowed position.
Hydraulics
What does the white PRESS light indicate on the RAT switch ?
- The RAT is deployed.
* The CENTER system primary flight control hydraulic pressure is > 3000 psi.
Hydraulics
What would cause automatic RAT deployment in flight ?
- Both engines have failed,
- All 3 HYD system pressures are LOW,
- Loss of all electrical power to CPT and F/O’s flight instruments,
- Loss of all 4 EMPs (Electric Motor Driven Pumps) and faults in the flight control system occur on approach,
- Loss of all 4 EMPs and an engine fails on take off or landing.
Hydraulics
Once deployed, can the RAT be restowed in flight ?
NO
Hydraulics
Which hydraulic system contains isolation functionalities ?
The center hydraulic system has isolation functionality to ensure key systems remain operational in the event of a hydraulic leak.
Hydraulics
What does the hydraulic isolation system ensure ?
It ensures the flight crew can lower the landing gear and that nose wheel steering remains operational.
Hydraulics
How many isolation valves does the isolation function use ?
3
• Nose gear isolation valve (NGIV)
• Reserve steering isolation valve (RSIV)
• Alternate extend isolation valve (AEIV not displayed on synoptic)
Hydraulics
Can the isolation valves from the isolation function be operated manually by the crew ?
NO, all isolation valves operate automatically.
Hydraulics
On the L and R hydraulic systems, what do the engine driven pump hydraulic supply shut off valves (SOVs) do ?
They are positioned between the reservoir and the engine driven pump (EDP) to isolate the pump from the hydraulic reservoir.
Hydraulics
How are the left and right shut off valves (SOVs) triggered ?
Through their respective engine fire switch :
When pulled out :
• The SOV closes
• The EDP is depressurized.
Hydraulics
How are the hydraulic reservoirs pressurized ?
By using pump outlet pressure.
