Chap 12: Aircraft Fluid Lines and Fittings

Question 1

what is flexible hose used for?

Answer 1

connect moving parts with stationary parts in location subjected to vibration or where flexibility is needed

Question 2

hose code for different pressures and sizes

Answer 2

MIL - H - 5593 (up to 600psi)
MIL - H - 8794 (up to 1500psi)
MIL - H - 8788 (up to 3000psi)

MIL - H - 8788 - 8: means 8/16” (1/2”) inside diameter that is used for high pressure applications

Question 3

different layers of hoses

Answer 3

inner layer: compatible with fluid transported (suitable material)
minimum amount of porosity

reinforcement: cover inner liner and determines hose strength
wire braid uses

outer cover: protect from physical damage or heat

Question 4

2 types of hose fittings

Answer 4

reusable end fittings:
socket, nipple and nut

swaged-on fittings:
cannot be removed and reused

Question 5

pressure proof test steps

Answer 5

cleaning and pressure testing

cleaned by compressed air blown in

and proof tested at 1.5 times the working pressure

Question 6

how to install flexible hoses

Answer 6

must not be twisted, and have a 5 - 8% slack (cannot be tight)

and torque nuts to correct value

Question 7

ways of testing the hoses

Answer 7

ball check: passing a ball through the hose to test for hose restriction

pressure test

cleanliness: after tested, hose should be flushed with white spirit and dried with clean dry air
caps/plugs to be used to close the ends after inspecting to prevent FODs