Unit 2-3

Question 1

What is the primary purpose of reservoirs?

Secondary purpose?

Answer 1

Supply fluid to pumps & System components

Thermal expansion
Air Purging
Filtration and sediment
Cooling of hydraulic fluid

Question 2

Describe non-pressurized reservoirs

Examples?

Answer 2

Vented to the atmosphere to allow air to dissipate from the system
Usually have a “standpipe”
So, outlet not at “bottom” of tank
May have filter built into them on the fluid return

Engine oil tank
Brake fluid reservoir
Radiator

Question 3

Describe pressurized reservoirs

Answer 3

For aircraft to fly to higher altitudes
Pressurizing minimizes foaming at lower atmospheric pressures

Usually marked purple

Question 4

What is the hydraulic accumulator?

What does it do?

Answer 4

A container to store hydraulic fluid under pressure

Provides a source of hydraulic power for back up or intermittent loads

Question 5

What two gases are typically used to pressurize an accumulator?

Answer 5

Air
Nitrogen

Question 6

What is the purpose of pumps?

Answer 6

Supply fluid flow to actuating units
Provide pressure to overcome system resistance

Question 7

When is an engine driven pump active?

What does it do?

Answer 7

Active any time the engine is running

Power the complete system
All the aircraft hydraulics

Question 8

When is an electric driven pump active?

What does it do?

Answer 8

Operated only when hydraulic pressure is needed
On-demand

Electric motor rotates pump to create hydraulic pressure and flow

Question 9

Describe gear pumps

Answer 9

Gears spin, fluid in one side and pushed out the other
Very robust

Question 10

Describe vane pumps

Answer 10

Mechanically driven through the engine
A lot more parts to break
Vanes can wear and tear, springs/vanes can get stuck and doesn’t effectively pump
Cavitation, air bubbles or fluid overflow caused by wear on the vanes
More effective than a gear pump
Better at moving mass amounts of fluid

Question 11

What are some advantages and disadvantages of vane pumps

Answer 11

Advantages:
More effective than a gear pump
Better at moving mass amounts of fluid

Disadvantages:
A lot more parts to break
Vanes can wear and tear
Springs/vanes can get stuck and not pump effectively
Cavitation, air bubbles or fluid overflow caused by wear on the vanes