Hydraulic Flashcards
The aircraft has three continuously operating hydraulic systems : blue, green, and yellow. Each system has its own hydraulic reservoir. Normal system operating pressure is
3 000 PSI (2 500 PSI when powered by the RAT). Hydraulic fluid cannot be transferred from one system to another.
GREEN SYSTEM PUMP
A pump driven by ___ pressurizes the green system.
engine 1
BLUE SYSTEM PUMPS
An electric pump pressurizes the blue system. A pump driven by ___ pressurizes this system in an emergency.
a ram air turbine (RAT)
YELLOW SYSTEM PUMPS
A pump driven by ___ pressurizes the yellow system.
engine 2
___ can also pressurize the yellow system, which allows yellow hydraulics to be used on the ground when the engines are stopped.
An electric pump
Crew members can also use a ___ to pressurize the yellow system in order to operate the cargo doors when no electrical power is available.
hand pump
POWER TRANSFER UNIT (PTU)
A bidirectional power transfer unit enables the ___ to pressurize the ___ and vice versa.
yellow system / green system
The power transfer unit comes into action automatically when the differential pressure between the green and the yellow systems is greater than ___
500 PSI
The PTU therefore allows the ___ to be pressurized on the ground when the engines are stopped.
green system
RAM AIR TURBINE (RAT)
A drop-out RAT coupled to a hydraulic pump allows the ___ to function if electrical power is lost or both engines fail. The RAT deploys automatically if AC BUS 1 and AC BUS 2 are both lost.
blue system
RAM AIR TURBINE (RAT) can be stowed only when
the aircraft is on the ground.
Priority valves cut off hydraulic power to heavy load users if
hydraulic pressure in a system gets low.
FIRE SHUTOFF VALVES
Each of the green and yellow systems has a fire shutoff valve in its line upstream of its engine-driven pump. The flight crew can close it by pushing the
ENG 1(2) FIRE pushbutton.
LEAK MEASUREMENT VALVES
Each 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.
RESERVOIR PRESSURIZATION
Normally, HP bleed air from ___ pressurizes the hydraulic reservoirs automatically.
If the bleed air pressure is too low, the system takes bleed air pressure from the crossbleed duct. The systems maintain a high enough pressure to prevent their pumps from cavitating.
engine 1
