1. Fluid Lines and Fittings
FAA-H chapter 7
General study guide questions 8192 – 8218
AC B

2. Fluid Lines
Fluid lines are made of metal tubing (rigid lines) or flexible hose.
Rigid lines for stationary applications
Aluminum for lower pressures
Stainless steel (CRS) for high pressure applications
Flex lines for items with relative motion between them.
Hose material depends on fluid type and pressure

3. Metal Tubing Sized by OD in 1/16 inch increments
A -4 hose or fitting is 4/16 or 1/4
-6 is 6/16 or 3/8
-8 is 8/16 or 1/2
Cut to 10% larger
Use special cutting tool
Use a deburring tool after cutting
Either single or double flare
Flared to a 37 degree angle
Not the same as automotive which is 35

4. Metal Tubing Lines marked with 1 inch tape or decals
At both ends of the line and in each compartment it passes thru
Tubing should always have at least one bend in it to absorb vibrations, expansion and contraction during operation

5. Fittings for Flared Tubing
2 piece AN818 nut and AN819 sleeve
Do not pull fitting into place with nut
Always use same alloy fittings
Do not overtighten, damage to flare will occur
Tighten till snug then one sixth turn
About on flat on the hex nut

6. Fittings for MS Flareless Fittings
Three parts
Body, sleeve and nut
The body and sleeve to cut into the tube when joined.
Overtightening will damage the tube

7. Damage to Tubing Any damage to the flare is unacceptable
Damage in the heel of the bend is usually not acceptable
Scratches or nicks by be repaired by burnishing with hand tools

8. Flexible Fluid Lines AC 4313 pg 9-18
Most common materials used for construction of hoses are;
Buna-N
Neoprene
Butyl
Ethylene Propylene Diene Rubber (EPDM)
Teflon

9. Flexible Fluid Lines Butyl Teflon
Used with phosphate ester based fluid such as SKYDROL
Never use with petroleum products
Five digit code for identification
Also used to identify if the hose is twisted during install
Teflon
Great operating range
Can handle a broad range of fluids
Permanent set, (cold flow) never straighten

10. Flexible Fluid Lines
Size corresponds to the outside diameter of rigid lines.
The ID of a hose is the same as the OD of a rigid line
5% to 8% slack
Install without twisting (lay line)
Watch minimum bend radius (43.13 fig 9-10)