Hydraulic Systems

Question 1

Equations Needed For Exam:

F=PA
P=F/A

Answer 1

Force = Pressure X Area
Pressure = Force / Area

Question 2

What does a hydraulic system do?

Answer 2

Hydraulic Systems use fluids to do work.

Question 3

What are some uses of hydraulics in aircraft?

Answer 3

•	Flight Controls 
      o	Primary flight controls
      o	Flaps
      o	Leading edge devices
•	Landing Gear
•	Brakes
•	NW Steering 
•	Thrust Reversers 
•	Air Stairs
Cargo Doors

Question 4

ARROW SPECIFIC HYDRAULIC SYSTEM USES: (4)

Answer 4

•	Landing Gear
•	Brakes
•	Propeller 
•	Gear Oleo Sruts (Landing Gear Struts)
        (hydraulic fluid flows to take some of the impact)

Question 5

Fluid: What happens in a hydraulic system.

Answer 5

Flows, and a fluid takes the shape of it’s container. Any substance which would yield to any force tending to alter it’s shape, having freedom of movement without separation from its mass & will take the shape of it’s container. (both gasses and liquids can be defined as fluids)

Question 6

Definition of a Liquid?

Do liquids expand wth heat?

Answer 6

any fluid having a definite volume and is non-compressible.

However, liquids do expand with heat.

Question 7

Hydrostatic Paradox:

Answer 7

It doesn’t matter how big a container is, it only matters how much weight is on top. Volume size shape don’t matter, it just matters what type of fluid is.

Question 8

Pascal’s Law

Answer 8

When is a force is exerted anywhere on a body of confined liquid, the pressure is transmitted AT ONCE and UNDIMINISHED & ALWAYS ACTS AT RIGHT ANGLES to the area of walls of the container.

Question 9

How large is a transmitted pressure? To answer this you need what?

Answer 9

(NEED PSI and FORCE)

Question 10

If you have two equal sized areas pushing it’ll push _______ amount of force

Answer 10

The SAME

Question 11

Hydraulic Fluid:

What is it’s viscosity
What temperatures does it operate to?
Can other components use it?

Details about A5606 which we use.

Answer 11

•	Low Viscosity
•	Goes to temperature extremes (120C – 248F)
•	Compatible with other components
•	AS 5606 (hydraulic fluid)
    o Mineral Based
    o	Flammable
    o	Non-Corrosive
    o	Red (arrow, Seminole) 
    o	Foams up

Question 12

Hydraulic reservoir

What does it do?
What does it serve as ?
What is often done to the reservoir and why ?
What does it prevent?

Answer 12

• Stores hydraulic fluid
• Serves as an expansion fluid
• Often pressurized to prevent foaming

Question 13

What does the hydraulic pump do?

Answer 13

• Provides necessary fluid movement.

Question 14

Typical Hydraulic Systems: Pressure

HIGH
MEDIUM
LOW

ARROW PRESSURE?

Answer 14

• High (3000PSI)
• Medium (1500 PSI)
• Low (400-800 PSI)
• Arrow Landing Gear Up (1300 PSI)

Question 15

Hydraulic Acccumulator:

What does it act as?
What does it do?
What does it utilize sometimes

What’s it’s purpose?

Answer 15

• Acts as a shock absorber
• Stores hydraulic fluid under pressure
• Utilizes compressible fluid (nitrogen) to maintain pressure

• Purpose:
o Dampens surges
o Backup pressure source
o Avoids back pressure shock

Question 16

Check Valves:

What do they do?
What are the three valves and what is their basic idea?

Answer 16

Make sure that fluid doesn’t back up

• Ball Check Valve
(one way flow, a ball piston and spring, ball plugs it and spring and piston hold it)

• Cone Check Valve (same concept)
• Swing Check Valve

Question 17

Relief Valve

How does it work?

Answer 17

• When the pressure reaches a predetermined value, allows fluid from the pressure side of system to be relieved into relief valve. Avoids over pressurization of the hydraulic system.

Question 18

Hydraulic Actuator :

What does it do?
What does it convert?
Can be two types what are they?

Answer 18

DOES THE WORK

• Converts hydraulic pressure & Flow into mechanical work
• Can be linear or rotary

Question 19

Filter

What does it do?

Answer 19

• Traps dirt and other sediment

Question 20

Seals: What doe they do?

Answer 20

: make sure we don’t lose our hydraulic fluid.

Question 21

Lines : What do they do?

Answer 21

Trasmit fluid and pressure throughout the system.

could be a 2 inch line or a 20 inch line, can still transmit same pressure