sleeves of flexible tubing securely held at each end. There  should be no relative movement at points where flexible  tubing is secured. These wires and the insulating tubing  should be inspected carefully at very frequent intervals, and  wires or tubing should be replaced at the first sign of wear.  There should be no strain on attachments when parts are fully  extended, but slack should not be excessive. deterioration at elevated temperatures. All high-temperature  areas should be avoided when installing these cables. Additional abrasion protection should be given to asbestos  wires enclosed in conduit. Either conduit with a high  temperature rubber liner should be used or asbestos wires  can be enclosed individually in high-temperature plastic  tubes before being installed in the conduit. Avoid installing wires in areas where they are subjected to  damage from fluids. Wires should not be placed in the lowest  four inches of the aircraft fuselage, except those that must  terminate in that area. If there is a possibility that wiring  without a protective nylon outer jacket may be soaked with  fluids, plastic tubing should be used to protect it. This tubing  should extend past the exposure area in both directions  and should be tied at each end. If the wire has a low point  between the tubing ends, provide a  1 ⁄ 8 -inch drainage hole.  [Figure 4-90]  This hole should be punched into the tubing  after the installation is complete and the low point definitely  established by using a hole punch to cut a half circle. Care  should be taken not to damage any wires inside the tubing  when using the punch. When wiring must be routed parallel to combustible fluid  or oxygen lines for short distances, as much separation as  possible should be maintained. The wires should be on a level  with, or above, the plumbing lines. Clamps should be spaced  so that if a wire is broken at a clamp, it will not contact the  line. Where a 6-inch separation is not possible, both the wire  bundle and the plumbing line can be clamped to the same  structure to prevent any relative motion. If the separation is  less than 2 inches but more than  1 ⁄ 2 inch, two cable clamps  back to back can be used to maintain a rigid separation only  and not for support of the bundle.  [Figure 4-91]  No wire  should be routed so that it is located nearer than ½ inch to a  plumbing line, nor should a wire or wire bundle be supported  from a plumbing line that carries flammable fluids or oxygen. Wiring should be routed to maintain a minimum clearance  of at least 3 inches from control cables. If this cannot be  accomplished, mechanical guards should be installed to  prevent contact between wiring and control cables. Wire should never be routed below a battery. All wires in the  vicinity of a battery should be inspected frequently. Wires  discolored by battery fumes should be replaced. Wires located in wheel wells are subject to many additional  hazards, such as exposure to fluids, pinching, and severe  flexing in service. All wire bundles should be protected by  Cable clamps should be installed with regard to the proper  mounting angle.  [Figure 4-92]  The mounting screw should  be above the wire bundle. It is also desirable that the back  of the cable clamp rest against a structural member where  practicable.  Figure 4-93  shows some typical mounting  hardware used in installing cable clamps. Be sure that wires  Figure 4-91.  Separation of wires from plumbing lines. Figure 4-90.  Drainage hole in low point of tubing. 4-54 Installation of Cable Clamps Protection of Wires in Wheel Well Area Protection Against Solvents and Fluids Routing Precautions