Fluid Lines & Fittings

Question 1

1. What are two types of commonly used fluid lines in aircraft plumbing?

Answer 1

Metal tubing & flexible hose and fittings

Question 2

2. How is metal tubing sized?

Answer 2

Outside diameter & wall thickness. OD measured in sixteenths of an inch

Question 3

3. What material should be selected for high pressure rigid fluid lines?

Answer 3

Annealed or 1/4 hard corrosion resistant steel

Question 4

4. What type of material should fittings be made of when used with stainless steel tubing?

Answer 4

Stainless Steel

Question 5

5. What percentage of flattening is allowed when bending metal tubing?

Answer 5

25% max

Question 6

6. What precautions should be taken when routing fluid lines adjacent to electrical wiring?

Answer 6

route fluid lines below the electrical wiring & maintain at least 6” whenever possible. Never have closer than .5”

Question 7

7. What is the purpose of the identification stripe running the length of a flexible hose?

Answer 7

Lay line. Shows if line is twisted or not.

Question 8

8. What are some synthetic materials commonly used to manufacture flexible hoses?

Answer 8

Buna-N
Neoprene
Teflon
Ethylene propylene diene rubber

Question 9

9. How are standard AN type & AC type fluid line fittings identified?

Answer 9

AN fluid line fittings are colored either blue or black while AC type fittings are gray or yellow

Question 10

10. What is the purpose of using quick disconnect couplings in fluid systems?

Answer 10

Quickly disconnecting a line without loss of fluid or air entering the system

Question 11

11. How is flexible hose sized?

Answer 11

Inside diameter in sixteenths of an inch

Question 12

12. How much slack must be left in a flexible hose during installation?

Answer 12

5-8% of total hose length for freedom of movement

Question 13

13. How often should flexible hoses be clamped in place?

Answer 13

Every 24 inches

Question 14

14. Name considerations when installing flexible hose assemblies?

Answer 14

Slack, flexing, twisting, bending, clearance, clamps

Question 15

15. What pressure is used to proof-test a flexible hose assembly?

Answer 15

1.5x the recommended operating pressure

Question 16

16. What are the three parts of a military standard MS tube fitting?

Answer 16

Body, sleeve, nut

Question 17

17. What will be the result of over tightening a flawless tube fitting?

Answer 17

Compression sleeve cutting edge will cut into the tube, weakening it

Question 18

18. What are the two kinds of flares used in aircraft plumbing systems?

Answer 18

Single flare & double flare

Question 19

19. What is the difference between automotive and aviation flares?

Answer 19

Aviation flares are 37 degrees Automotive are 45 degrees

Question 20

20. What is the advantage of a flexible teflon hose over a rubber hose?

Answer 20

Teflon - resistant to chemicals and higher strength at higher temps

Question 21

21. What precaution should be taken when deburring and inspecting the flared end of a tube?

Answer 21

No cracks & wall thickness is not reduced by deburring

Question 22

22. What type of rubber is used in flexible lines that carry phosphate ester hydraulic fluid?

Answer 22

Synthetic

Question 23

23. What type of information is on a hose lay line?

Answer 23

Hose type, quarter & year of manufacture

Question 24

24. What are the identification marks usually found on flexible rubber hose?

Answer 24

Lay line
Hose size
Manufacturer 
Date of manufacture
Pressure
Temperature

Question 25

25. What is the distance between hose identification markers?

Answer 25

9 inches