Figure 9-138.  Installing cable clamp to structure. Wire is pinched in clamp “Z” member “Angle” member Cable clamps Angle bracket Incorrect Correct Clamps lined with nonmetallic material should be used to  support the wire bundle along the run. Tying may be used  between clamps, but should not be considered as a substitute  for adequate clamping. Adhesive tapes are subject to age  deterioration and, therefore, are not acceptable as a clamping  means.  [Figure 9-137] ducts, or conduits. The supporting devices should be of a  suitable size and type, with the wires and cables held securely  in place without damage to the insulation. Use metal stand-offs to maintain clearance between wires and  structure. Tape or tubing is not acceptable as an alternative to  stand-offs for maintaining clearance. Install phenolic blocks,  plastic liners, or rubber grommets in holes, bulkheads, floors,  or structural members where it is impossible to install off- angle clamps to maintain wiring separation. In such cases,  additional protection in the form of plastic or insulating tape  may be used. The back of the clamp, whenever practical, should be rested  against a structural member.  [Figure 9-138]  Stand-offs  should be used to maintain clearance between the wires and  the structure. Clamps must be installed in such a manner  that the electrical wires do not come in contact with other  parts of the aircraft when subjected to vibration. Sufficient  slack should be left between the last clamp and the electrical  equipment to prevent strain at the terminal and to minimize  adverse effects on shock-mounted equipment. Where wires  or wire bundles pass through bulkheads or other structural  members, a grommet or suitable clamp should be provided  to prevent abrasion. When a wire bundle is clamped into position, if there is less  than  3 ⁄ 8-inch of clearance between the bulkhead cutout and  the wire bundle, a suitable grommet should be installed as  indicated in  Figure 9-139 . The grommet may be cut at a 45°  angle to facilitate installation, provided it is cemented in place  and the slot is located at the top of the cutout. Properly secure clamp retaining bolts so the movement of  wires and cables is restricted to the span between the points  of support and not on soldered or mechanical connections at  terminal posts or connectors. Clamping of wires routed near movable flight controls  must be attached with steel hardware and must be spaced  so that failure of a single attachment point cannot result in  interference with controls. The minimum separation between  wiring and movable controls must be at least  1 ⁄ 2 inch when  the bundle is displaced by light hand pressure in the direction  of the controls. Inspect wire and cable clamps for proper tightness. Where  cables pass through structure or bulkheads, inspect for proper  clamping and grommets. Inspect for sufficient slack between  the last clamp and the electronic equipment to prevent strain  at the cable terminals and to minimize adverse effects on  shock-mounted equipment. Wires and cables are supported  by suitable clamps, grommets, or other devices at intervals of  not more than 24 inches, except when contained in troughs,  Conduit is manufactured in metallic and nonmetallic  materials and in both rigid and flexible forms. Primarily,  its purpose is for mechanical protection of cables or wires.  Conduit size should be selected for a specific wire bundle  application to allow for ease in maintenance, and possible  future circuit expansion, by specifying the conduit inner  diameter (ID) about 25 percent larger than the maximum  diameter of the wire bundle.  [Figure 9-140] 9-83 Conduit Wire and Cable Clamp Inspection  Movable Controls Wiring Precautions