Hydraulic System Flashcards
(20 cards)
Where can hydraulic quantity and pressure be monitored?
Can be monitored on STATUS display or hydraulic synoptic display.
After engine start, under what circumstances would you expect the left or right demand pumps to run?
- System low pressure
- On the ground, 3 minutes after second engine start
- Takeoff thrust set to flaps retracted
- From gear down or RA less than 1000’ to GS less than 40kts
- During thrust reverser operations
After engine start, under what circumstances would you expect the center demand pump to run?
- System low pressure
- On the ground, 3 minutes after second engine start
- Takeoff thrust set to RA >2000’
- From gear down and RA less than 2000’ to GS less than 60kts
- Flaps or slats in motion
Why does the center system have an isolation feature?
To preserve system functionality in the event of a leak, allowing crew to be able to lower landing gear and have nose gear steering on landing roll.
When does the RAT deploy automatically?
- Both engines have failed
- All three hydraulic system pressures are low
- Loss of all electrical power to the CPT & FO flight instruments
- Loss of all 4 EMP’s and faults in the flight control system occur on approach.
- Loss of all 4 EMP’s and an engine fails on takeoff or landing.
When will a hydraulic pump FAULT light illuminate?
- Low primary pump pressure
- Excessive pump fluid temperature
- Pump is selected off
Will a hydraulic pump shutdown/stopped by system logic (i.e. Before engine start etc) cause the FAULT light to illuminate?
No. A pump manually selected OFF will illuminate the FAULT light.
With the C1 demand pump switch selected on, when will the pump run?
Continuously
Which systems are powered by the center hydraulic system?
- Flaps/Slats
- Landing gear actuation
- Nose wheel steering
- Flight controls
Which systems are powered by the Left and Right hydraulic systems?
Flight controls and the respective side thrust reverser
Will the OF and RF indications show in the air?
No, only on the ground
Below what value will the hydraulic pressure display in amber in the synoptic display?
Below 3000psi
When does the RAT “PRESS” light illuminate?
When the system pressure for the flight controls is higher than 3000psi
What determines which Center pump will be primary and which will be demand?
Day of the week from the FMC
Below what pressure is an EMP displayed in amber as failed on the synoptic display? EDP?
EMP - amber below 2000psi
EDP - amber below 2150psi
Which hydraulic systems have an isolation functionality?
Center system only
What is the purpose of the accumulators in the hydraulic systems?
- Absorb pressure changes during operation
- Keep positive bootstrap pressure in system when pumps do not operate. This prevents pump cavitation on startup.
How are the hydraulic systems cooled?
By heat exchangers in the main fuel tanks.
Each system has one heat exchanger in its respective tank, Center system has one heat exchanger in each tank.
What is the purpose of the reservoir suction shutoff valve in the left and right systems?
- Ensures system doesn’t lose all hydraulic fluid if there is a leak in the tubing to the EDP.
- Fluid will be shut off to EDP ensuring EMP has enough remaining in the tubing to operate flight controls.
What is the purpose of the reservoir suction shutoff valve in the center system?
- Ensures system doesn’t lose all hydraulic fluid if there is a leak in the tubing to the EMP C2. (MLG and flight controls)
- Fluid will be shut off to EMP C2 ensuring EMP C1 has enough remaining in the tubing to operate nose wheel steering and flaps.
