Hydrulic & Pneumatic Power Systems

Question 1

1. What are the three principal categories of hydraulic fluids?

Answer 1

Mineral (5606)
Phosphate ester (Skydrol)
Polyalphaolefin (83282)

Question 2

2. What is the color of mineral based hydraulic fluid?

Answer 2

Red

Question 3

3. How do you determine which type of hydraulics fluid to use in a specific system?

Answer 3

Aircraft maintenance manual or plate attached to reservoir

Question 4

4. What will happen to the seals in a vegetable bees hydraulic system if it is serviced with mineral or phosphate ester based fluids?

Answer 4

Seals will swell, break down, & block system

Question 5

5. When installing a chevron seal what must be considered?

Answer 5

Seal is directional & install with pressure going toward the open side of seal

Question 6

6. When hydraulic lines have been disconnected, what precaution should be taken to prevent contamination of the system?

Answer 6

Hyd. Lines & fittings should be capped or plugged immediately

Question 7

7. What happens to the hydraulic fluid flow if the filter element becomes clogged with foreign matter?

Answer 7

Bypass valve routes hydraulic fluid from inlet to outlet port

Question 8

8. What is a micro filter?

Answer 8

Filter with paper element

Question 9

9. Name the filters used in aircraft pneumatic systems?

Answer 9

Paper pleated & screen type

Question 10

10. Why are some hydraulic reservoirs pressurized?

Answer 10

Ensure positive flow to the pumps & high altitudes

Question 11

11. What methods are used to pressurize hydraulic reservoirs?

Answer 11

Variable displacement pump
Engine bleed air
Hydraulic system pressure on piston in reservoir
Aspirator or Venturi

Question 12

12. What are the two types of accumulator housing?

Answer 12

Spherical & cylinder

Question 13

13. Name three types of hydraulic accumulators?

Answer 13

Diaphragm
Bladder
Piston

Question 14

14. What is the purpose of a pressure relief valve in a.hydraulic system?

Answer 14

Limit amount of pressure within the system

Question 15

15. What is the purpose of an unloading valve in a hydraulic system?

Answer 15

Provides low pressure path from pump to reservoir when system has not flow requirements

Question 16

16. What is the function of a wing flaps overload valve?

Answer 16

Prevents structural damage to the flaps from lowering at excessive speeds

Question 17

17. What is the purpose of the shear-able section in a hydraulic pump?

Answer 17

Disconnect the pump from engine so engine can run

Question 18

18. What are two different types of hydraulic pumps?

Answer 18

Hand & power pumps

Question 19

19. What pump is most suitable for low pressure pneumatic systems?

Answer 19

Vane Type pump

Question 20

20. What protects a direct pressure type hydraulic pressure gauge from pressure surges?

Answer 20

Dampening device (small restrictor)

Question 21

21. What are pneumatic systems used for in aircraft?

Answer 21

Operate brakes
Open close doors
Starting
Pump driving
Emergency devices

Question 22

22. What happens to the air after a pneumatic system is operated?

Answer 22

Air is dumped overboard

Question 23

23. Why should a pneumatic system be purged periodically?

Answer 23

Remove contamination, moisture, or oil from components & lines

Question 24

24. What is the purpose or the relief valve in a pneumatic system?

Answer 24

Protects against over pressurization

Question 25

25. What is the purpose of an accumulator?

Answer 25

Prevent hydraulic system shock when under high load demand

Question 26

26. What would cause a hydraulic filter to go into full bypass mode allowing unfiltered fluid into the system?

Answer 26

Clogged filter