AGK systems Lesson 2 Flashcards
Input force x input distance =
output force x output distance
A Smaller piston displaces a volume equal to area multiplied by?
the distance moved (its stroke)
Force =
area x pressure
area x pressure =
force
Passive hydraulic systems use _____ _____ to raise pressure
Passive hydraulic systems use human power to raise pressure
Active hydraulic systems use one or more _____
pumps
Closed centered systems provides
Constant pressure all the time
Active systems can supply:
Constant pressure all the time - closed centered systems
Pressure only when demanded - open centered systems.
Open centered systems provides
Pressure only when demanded -
What fulid do we put into an aircraft system?
Correct specification from an unopened container.
Hydraulic fluid must have these properties:
Low viscosity to allow it to flow freely through the system
Resistance to foaming or creating sludge
Good lubrication qualities
Corrosion resistance
Resistance to heat and thermal stability across the temperature range
High boiling point and low freezing point (e.g., +80°C to -70°C)
Chemically inert
Non-flammable with a flash point above 100°C
Good storage properties.
Hydraulic fluid is available in two common forms:
Synthetic
Hydro-carbon based - Used in systems with butyl rubber/Teflon seals – may be Orange in colour
Phosphate Ester (Synthetic) – Skydrol – usually purple in colour
Mineral
For example DTD 585 which is coloured red
Hydraulic fluids can be very _________ so avoid contact and wear protective clothing
corrosive
Which hydraulic fluid is red?
Mineral Based
Kerosene
Red
Suitable for high pressure systems
Good resistance to foaming
High Boil and Flash Point although flammable
Synthetic rubber seals
Which hydraulic fluid is purple?
Synthetic Based
Phosphate Ester
500A purple in colour
Skydrol
3 Grades in use
500 500A 700
Can be used at very high pressures
Must only be used with the following:
Butyl Rubber Ethylene Propylene
Teflon seals
Advantages of Hydraulic Systems
Excellent for providing large amounts of power
Very little energy is lost in the transmission process
Other advantages include:
> Leaks are relatively easy to spot
Reduced weight when compared to mechanical system
Provide large amounts of force to operate heavy services.
Disadvantages Hydraulic System
The fluid is highly corrosive
The forces generated can require strong structures
Large systems can be quite heavy
Susceptible to fluid contamination
Damage to hydraulic lines
Hydraulic fluid is health risk and environmentally hazardous.
What are the basic components of a hydraulic system
Reservoir
Accumulator
Pump
Double acting cylinder
Non return valves
4 port rotary selector valve
What is the operating range of a hydraulic system?
3000 - 4000psi
Does a hydraulic cylinder provide the same force in both directions?
No, the area is different in each direction due to the rod coming out of the system
Reasons for hydraulic pump failure
Electrics
Engine
No fluid
What does an actuator do?
Convert hydraulic pressure into movement
What’s the difference between single and double acting hydraulic actuators?
Single is pushing against a spring and has one feed.
Double has a double feed, the fluid pushes the piston in each direction?
What are the types of selector valves?
Closed centre selector
Open centre selector
Linear (spool) valve selector
