11.11 Hydrualic Power Flashcards
How do you calculate pressure?
Force/ Area
What pressure do civil aircraft hydraulic systems work at?
3000psi or 207 bar
What are the two types of hydraulic pressure?
. Hydrostatic pressure
. Hydrodynamic pressure
100KPa = ?
1DN/cm2
1 bar = ? Psi
14 psi
3000 psi = ? Bar
207 bar
What are the two types of hydraulic fluids?
Mineral oil
Synthetic oil
What colour is mineral oil?
Red
What colour is synthetic oil?
Violet
Can mineral and synthetic oil be mixed?
No
What is the specification for mineral and synthetic oil?
MIL-H 5606
What prefix’s do Boeing and airbus use?
Boeing = BMS
AIRBUS = NSA
What are the advatanges of hydraulic fluids?
. Low flammability
. Good lubricatuon
. Resistance to freeze
. Non evaporating
. Non foaming
. Chemical stability
What is the disadvantage of hydraulic fluid?
Hydroscopic quality
(Tendency to absorb water)
Which oil is better, mineral or synthetic?
Synthetic
What is the purpose of packing (back up ring)?
. Prevent leaks
. Separates the different fluid pressures
In high pressure areas, one seal may not be enough, so what would you use?
A backup ring
What are seals and back up rings made from?
Seals = rubber
Backup ring = Teflon
What are the two purposes of hydraulic reservoir?
. Compensate for variations in amount of hyduakid fluid needed from systems
. Keeps reserve of hydraulic fluid incase of a leaks
Where would you use static seals?
Static seal - used to seal against steady or pulsating pressures
What is used to prevent hyduakic fluid moving upwards if regret is a sudden loss of pressure?
(Stops sloshing)
A sheet metal baffle
When is the drain valve located on resivour?
Lowest part to allow emptying
Why is the hydraulic reservoir pressurised?
To ensure a positive supply of hydualic fluid always reaches the pumps
Prevents, foaming, evaporation, cavitation
What colour hydraulic system does electrical pump produce?
Blue hydraulic system
Once the RAT push button is activated in cockpit how long till it deploys?
Less than 1 second
What is the purpose of the priority valve?
Closes the hydraulic circuit ti different users when there is a very high demand in system
(Not part of manifold)
What does an accumulator do?
Acts as a damper to smooth out pressure fluctuation in the system caused by sudden user demand
Where is the sampling valve for fluid sampling located and what is the purpose of it?
. A sampling valve is located in the HP manifold
. Checks for water contamination no reduction in fluid performance
When doing a leak test, what does it test for and where does it not test?
Tests in main user components such as flight controls
Does not test pressurisation or distribution components
What pressure do the resivours run at?
50 psi
What is the hydraulic system measured in?
Bar
What connects reservoir to pumps?
Supply lines
What hydaulic fluid is better?
Synethic
What psi do vertical displacement pumps run at?
3000psi
Why do we need filters?
Stops FOD damaging components
Filters also have a screen device
When a leak is detected what shuts the valve?
A leak measurement solenoid valve
What differs the fixed displacement pump and the variable pump?
Variable has a wobble plate which means the angle of wobble can be changed
Fixed doesn’t
Where is the depressurised valve located?
At ground service panel
Where is the quantity transmitter located in the resivour and how does it operate?
. Located on the side of resivour housing
. Uses calamities to measure fluid level for cockpit to see
What is the purpose of power transfer unit?
Another method of providing auxiliary pressurisation
Transfers hydraulic power between two systems, no fluid is transferred.
What is another name for electric pump?
Demand pump
What is the leak measurement manifold connected to?
The pressure line supplying to users
What does the LP manifold do?
Connects all return lines into a single line going back to the reservoir
What does the term high pressure distribution describe?
The process of moving the pressurised fluid from hydraulic pumps to hydraulic users
Where would you use dynamic seals?
Dynamic seal - used to seal where stroking or rotational movements
