Hydraulics Flashcards
What does the hydraulic system consist of?
Two engine driven hydraulic pumps
A hydraulically driven suction boost pump
A hydraulic reservoir
Power transfer units
Two ATM pumps (supplies hydraulics for flight and ground ops)
RAT pump (supplies #2 hydraulic pressure in event of total power failure)
Electric suction boost pump
Where can you service the hydraulics in-flight?
#3 service center through a selector valve, fluid receptacle and hand pump (right side cargo compartment)
A ground fill connection in the right MLG fairing (external servicing)
How is the hydraulic fluid cooled?
Each hydraulic system is equipped with a heat exchanger for fluid cooling.
The heat exchangers for hydraulic systems No. 1 and No. 2 are installed in the No. 2 main fuel tank.
The heat exchangers for hydraulic systems No. 3 and No. 4 are installed in the No. 3 main fuel tank.
Hydraulic fluid from the engine driven and ATM driven pumps case drain is drawn through the heat exchangers to maintain a temperature of:
130 - 150 F
How much fuel is required for hydraulic cooling?
18000 lbs (heat exchangers are only in tanks #2 and #3 and each tank must have at least 4500 lbs of fuel in it; to ensure balanced fuel tanks the #1 & #4 tanks must also have 4500 lbs thereby totaling 18000 lbs
How many engine driven Hydraulic pumps are installed on each engine?
2 (61 GPM, variable displacement)
What is the purpose of the hydraulic suction boost pump?
Prevents cavitation of the engine driven pumps by providing pressurized fluid from the unpressurized reservoir to engine-driven pumps
Where does the hydraulic suction boost pump get its operating pressure?
From the engine–driven pumps (top/bottom) which it supplies and will operate as long as there is hydraulic pressure supplied to the system
When and why are the electric suction boost pumps used for during engine start?
For engines 1 and 4 only, used for engine start, ground ops and takeoff & landing to pressurize the suction lines to engine driven pumps and ATMs.
Are the hydraulic reservoirs pressurized?
No
What is a PTU and how does it work?
Power Transfer Unit
It takes hydraulic pressure from one system and provides pressure to the adjacent system without mixing hydraulic fluid between systems. It is basically two constant displacement motors connected through an internal shaft.
When are the PTUs energized?
When demands are greatest; emergency ops, ground maintenance and takeoff/landing
What is an ATM?
Provided to supply hydraulic pressure to systems 1 & 4 during ground operation or for maintenance purposes and for emergency in-flight operation. The ATM pumps are 40-GPM pumps and are controlled by switches on the flight engineer console
How does the ATM provide hydraulic pressure?
It uses bleed air from an APU, an external source, or the main engines to drive the pump which provides the hydraulic pressure.
How many ATMs are installed on the C-5 and what hydraulic systems to they supply pressure to?
Two: Right ATM pressurizes system 4, Left pressurizes system 1.
What is the RAT and what is it used for?
Ram Air Turbine
A Ram Air Turbine (RAT) pump is provided to supply pressure to hydraulic system No. 2. The RAT provides capability for airplane control using limited flight controls for the time required to restart the engines or ATM pumps. It is deployed on the left side of the aircraft aft of the crew entrance door and forward of the main gear wheel well. The airstream drives the turbine and turns the hydraulic pump.
How is the RAT deployed?
AUTO: In the AUTO position the RAT will automatically deploy in flight if both inboard and either outboard engine is shut down or falls below IDLE N2. The RAT in-flight mode is set when the strut pressure switches on either MLG No. 1 and No. 3, or MLG No. 2 and No. 4 are in the air position.
MANUAL: RAT switch is placed to DEPLOY on Pilot Instrument Panel
OVERRIDE: A guarded emergency RAT deployment Override Pushbutton, located in the No. 2 hydraulic service center is used to deploy the RAT in the event the AUTO or DEPLOY positions of the Ram Air Turbine switch do not deploy the RAT.
Deploying the RAT de-energizes which PTU?
1-2 PTU
In the AUTO position inflight, the RAT will automatically deploy when:
The two inboard engines and either outboard engine are shut down or fall below IDLE N2.
The RAT’s AUTO position is energized through a combination of four pressure switches and is operable only when the airplane is __________
In flight
Will the RAT deploy in AUTO if you shut off all 4 engines in the chocks?
NO; The AUTO position is operable only when the airplane is in flight; 1 switch per bogie