Carefully inspect all hydraulic hose and fittings at regular times to make sure airworthiness. Investigate any proof of fluid loss or leaks. Check metal tubes for leaks, loose anchorage, scratches, kinks, or any other damage. Inspect fittings and connections for leakage, looseness, cracks, burrs, or any other damage. Replace or repair defective elements. Make certain the hoses don’t chafe against each other and therefore are properly guaranteed and clamped.
a. Substitute of Metal tube. When inspection shows hydraulic hose to become broken or defective switch the entire line or, when the broken section is localized, a repair section might be placed. In replacing aircraft hose, always employ tubing of the identical size and material because the original line. Make use of the old tubing like a template when bending the brand new tube, unless of course it’s too greatly broken, by which situation a template can be created from soft iron wire. Soft aluminum tubing (1100, 3003, or 5052) under half-inch outdoors diameter might be bent by hands. For those other tubing make use of an acceptable hands or power tube-bending tool. Bend tubing carefully to prevent excessive flattening, kinking, or wrinkling. A tiny bit of flattening in bends is suitable, but don’t exceed 75 % from the original outdoors diameter. Excessive flattening may cause fatigue failure from the hydraulic tube. When installing the substitute tubing line up properly using the mating part that it is not forced into alignment by tightening from the coupling nuts.
b. Hose couplings and Tube Connections. Many tube connections are created using flared tube ends with
standard connection fittings: AN-818 (MS 20818) nut as well as an-819 (MS 20819) sleeve. In developing flares, cut the tube ends square, file smooth, remove all burrs and sharp edges, and completely clean. The tubing will be flared while using correct 37-degree aviation flare developing tool is bigger of tubing and kind of fitting. A dual flare can be used on soft aluminum tubing 3/8-inch outdoors diameter and under, along with a single flare on other tubing. For making the connections, use hydraulic fluid like a lubricant after which tighten. Overtightening will damage the tube or fitting, which might result in a failure. Under-tightening could cause leakage which could cause a method failure.
CAUTION: Mistaken utilization of 45-degree automotive flare developing tools may lead to improper tubing flare shape and position causing misfit, stress and strain, and probable system failure.
c. Repair of aircraft hydraulic Metal Tube Lines. Minor dents and scratches in tubing might be repaired. Scratches or nicks not much deeper than 10 % from the wall thickness in aluminum alloy tubing, that aren’t within the heel of the bend, might be repaired by burnishing with hands tools. Replace lines with severe die marks, seams, or splits within the tube. Any crack or deformity inside a flare is unacceptable and reason for rejection. A dent or dimple under 20 % from the tube diameter isn’t objectionable unless of course it is incorporated in the heel of the bend. A seriously-broken line ought to be replaced however, it might be repaired by eliminating the broken section and inserting a tube portion of the same size and material. Flare both sides from the undamaged and substitute tube sections making the bond by utilizing standard unions, sleeves, and tube nuts.When the broken portion is brief enough, omit the insert tube and repair by utilizing one union and 2 teams of connection hose fittings.