Hydraulic Flashcards
How many hydraulic systems are there ?
3 independant systems : GREEN - BLUE and YELLOW
What is the normal operature pressure ?
3000 PSI
What is the normal operature pressure when RAT extended ?
2500 PSI
Can the hydraulic fluid be transfered from one system to another ?
No transfer of fluid between the system to prevent contamination
What are the hydraulic pumps ?
GREEN : engine-driven by ENG 1
BLUE : electrical pump + another pump driven by the RAT in case of emergency
YELLOW : engine-driven by ENG 2 + electrical pump allows yellow system to be used on the ground with engines stopped. Crew can also use a handpump to operate the cargo door operation when electrical power is not available
What is the role of the PTU ?
It enables to GREEN system to power the YELLOW system and vice versa
When does the PTU come into action ?
If one system fails or if the pressure drops at least 500 PSI more than the other pump.
What is the purpose of the priority valves ?
They are installed to maintain hydraulic pressure to the primary flight controls and cut off pressure to the heavy loads (landing gear for example) if the hydraulic pressure in a system gets low (during high demand)
What is the purpose of the accumulators ?
They are designed to maintain a constant pressure by covering transcient demands
How are the FIRE shut off valves activated ?
When the FIRE pb is pushed
What is the purpose of the leak measurement valves ?
Upstream of the all the flight controls or system, they check the total leakage of the hydraulic components
How is the reservoirs pressurized ?
Normally by the HP bleed air coming from the engine 1.
If bleed air pressure is too low, the system takes bleed air from the crossbleed duct.
When is the YELLOW ELEC pump inhibited ?
When a ground crew sets the lever of the cargo doorr manual selector to OPEN to CLOSE, yellow elec pump automatically comes ON, which inhibits the other function of the yellow elec pump
What is not included in the YELLOW ELEC pump inhibition ?
Alternate braking and engine 2 reverse.
When is the PTU tested ?
After the second engine is started
When is the PTU inhibited ?
- the YELLOW ELEC pump is operated to close the cargo door and is kept inhibited 40 seconds after the end of the cargo door operation
- the aircraft is on the ground with one engine runung and parking brake ON
- the aircraft is on the ground with one engine running, parking brake OFF and nose wheel steering deactivated
- the PTU pb is OFF
- During the first engine start
What does the RAT MAN ON pb do on the HYD panel ?
It enables the crew to energize the emergency hydraulic pump ONLY. It does not activate the emergency electrical generator
How many liters are there in normal filling in the reservoir ?
GREEN : 14,5L
YELLOW : 12,5 L
BLUE : 6,5 L
When does the system pressure become amber on the SYS page ?
When pressure is below 1450 PSI
When does the PUMP become amber on the SYS page ?
When N2 is below IDLE
