Hydraulic System Flashcards
Hydraulic System
3 systems
Use skydrol
Operate at 3000psi
Main Components are
2 Engine driven pumps
4 AC pumps
1 PTU hydraulic power transfer unit
3 hydraulic reservoirs
Systems 1&2
Powered by 1 Engine driven pump each
Backed up by 1 AC pump each
Usage of the electric pumps
Electric Hydraulic pumps are used during Take off & Landing and in the event of engine or engine driven pump failure.
PTU is installed between the 2 systems to transfer Hydraulic power from System 1 to 2 without mixing fluid between the systems.It is used for landing gear retraction and extension if the engine driven pump at System 2 fails
PTU WILL NOT OPERATE IF airspeed <50kts and when on the ground
Electric pumps are used in TO & Landing to avoid any disturbances if an engine driven pump or an Engine failure occurs. They are activate when :
Flaps extended
Groundspeed >50kts
Thrust Levers to Take Off
And minimizing the effect of switching to the back up pump.
System 3 will not be affected by the loss of an engin power.
System 3 operation
By
1 main hydraulic pump
1 auxiliary electric hydraulic pump as a back up
The system philosophy
It is designed so even the in case of 2 systems failure the 3rd to be operational for the flight critical functions.
System 1 operates
Left Outboard Elevator PCU
Rudder Upper PCU
Engine 1 Reverser PCU
MF spoiler 3/4
GND Spoiler 2
Brake Outboard
Emergency Parking Brake
System 2 powers
Left & Right Elevator PCUs
Left & Right Aileron inboard PCU
Engine 2 Reverser
MF Spoiler 5
GND Spoiler 1
Brake Inboard
Nose Wheel STR
Emergency Parking Brake
Landing Gear
System 3 powers
Right Elevator outboard PCU
Rudder Lower PCUs
Left & Right Outboard PCU
How to control
From the flight deck
4 rotary knobs for the AC pumps
1 rotary knob for the PTU
2 Guarded buttons for the firewall shutoff valves
AC pump knob positions
When in AUTO 1,2 they turn On automatically during TO and Landing or when primary pump pressure is lost.
Pump 3B activates automatically when 3A fails and is not activated during TO & Landing.
PTU
In case end2 or edp2 fails, the PTU is activated automatically when in AUTO position and NOT Flaps0
The ON selection
We can turn it to ON in case the SPDA goes Offline
Overheat condition can be caused by
A pump compensator failure -> rapid rise of hydraulic fluids temperature
System 3A&3B switches off automatically when temp. reaches 125celsius
What is an SPDA
Secondary Power Distribution Assembly