ABOUT HOSES ( http://aviationinspection.com)

General condition

Deterioration of a hose is characterized by discolorations, flaking, hardening and crazing. Installation should be checked to ensure that any supports or clips are correctly fitted with no corrosion or chafing underneath them, and the hose is not twisted or stressed.

a.    Kinks and Twists This defect is usually caused by incorrect installation or handling, is permanent damage restricting flow and the hose should be replaced.
b.    Broken Braids Isolated random breakage of the braid wires is a minor defect. If breakage of several wires are concentrated in one area, or two or more wires in a braid is broken, it is a major defect.
c.    Chafing and cuts Light scuffing, cuts and abrasion of the outer cover, with the braids not exposed is a minor defect. Minor adjustment of the hose clamps to avoid chafing is recommended, (unless otherwise approved clamping of pipes should be in accordance with aircraft type design)
d.    Corrosion Light local corrosion of braids and end fittings, due to oxidation or chemical attack, may be a minor defect to be monitored in subsequent inspections.
e.    Brittleness High temperatures and long service may harden hoses and make them brittle and should be replaced. This may also point to incorrect type of hose for the application and should be investigated.
f.     Contamination Instances of significant hardening, discoloration or sponginess of the outer rubber cover may indicate chemical contamination and could require replacement of the hose.
g.    Leakage Any leakage from fittings that retains the flexible element is a major defect and the hose should be replaced.
h.    Damaged fire sleeve Localized cuts and abrasions where the hose is not exposed is a minor defect for further monitoring.
i.      Blisters Puncture the blister and if the operating fluid leaks out, it is a major defect.

Testing of Hoses

1.       During overhaul or major refurbishment of the engines, all hoses should be tested. A test interval of six years is recommended for airframe hoses.

2.      Before testing hoses should be inspected per paragraph 5.1 of this AWB. In general the serviceability criteria for hose assembly when not installed (ie at piece part level) should be more stringent than when it is installed on the aircraft. Removable fire sleeves should be removed during this inspection.

3.      Hoses should be tested for internal restriction or kinking by passing a steel ball in both directions. Refer FAA AC 43.13-1B CHG 1 for the size of the ball to suit various hose sizes. In general a steel ball the diameter of which is approximately 90 percent of the bore of the end fitting will be adequate for this test.

4.      Hoses should be hydraulic pressure tested at 1.5 times the maximum system pressure without leakage.

5.      Vacuum hoses should be tested to 28 inches of mercury vacuum and the hose should not collapse after it has been tested for leakage per paragraph 7.3.

6.      Hoses with Teflon lining, or hoses that have undergone a permanent set should be restrained in their preset shape using lock wiring during the test to ensure that they do not flex.

7.      After test, the hose should be cleaned, ends blanked and marked with the date of test, and test pressure, along with direction of fluid flow and type of fluid where applicable. Data may be stenciled on the external surface, or impressed on a metal band secured to the hose.

8.     Hoses should be suitably preserved. Restraint per paragraph 7.5 should be retained during transport and storage.