TM 1-1500-204-23-4 CHAPTER 3 ELECTRICAL MAINTENANCE PRACTICES 3-1.    Installation  Inspection  of  Wires  and  Cables. Installation    inspection    of    wires,    cables,    and    their components  is  explained  in  the  following  paragraphs. Refer   to   TM      55-1500-323-24   for   wire   maintenance practices. a. Inspection   Requirements.      Wires   and   cables shall  be  inspected  for  adequacy  of  support,  protection, and  general  condition  throughout.    The  desirable  and undesirable features in aircraft wiring are outlined below and  indicated  as  conditions  that  should  or  should  not exist.  Inspect aircraft wiring as follows: (1) Ensure wires and cables are supported by cushion  clamps,  grommets,  or  other  approved  devices, at  intervals  of  not  more  than  24  inches,  except  when contained in troughs, ducts, or conduits.  The supporting devices  must  be  of  a  suitable  size  and  type,  and  the wires and cables must be held securely in place without damage to the insulation. (2) Provide adequate stand-off support where wires  are  routed  over  any  structural  member  in  such  a manner  that  chafing  is  likely  to  occur.    Ensure  that  the use  of  proper  insulating  material,  is  wrapped  over  wire or cable to protect against chafing, is not being used in applications where stand-off supports could be installed. (3) Ensure  phenolic  blocks,  plastic  liners,  or rubber  grommets  are  installed  in  holes  in  bulkheads, floors, or structural members through which wiring must pass  and  it  is  impossible  to  install  off-angle  clamps  to maintain  wiring  in  a  fixed  position  away  from  edges  of holes.  In such cases, additional protection, in the form of plastic tubing or insulating tape is optional. (4) Ensure    wires    and    cables    in    junction boxes, panels, and bundles are properly supported and laced to provide proper grouping and routing. WARNING Make  sure  any  retaining  screw  or bolt protruding through bulkheads, panels, etc.  , does not interfere with flight controls fluid/fuel lines or any other component. (5) Ensure clamps and retaining screws are properly mounted and secured so that any movement of wires and cables is restricted to the span between points of  support.    Movement  of  wires  and  cables  should  not be  transmitted  to  soldered  or  mechanical  connections such as terminal posts or connectors. (6) Check that wires and cables are supported   and   bound   so   that   interference   with   other wires, cables and equipment does not exist. (7) Check that wires and cables are adequately  supported  to  prevent  excessive  movement in areas of high vibration. (8) Ensure    insulating    tubing    and    tape    is secured in place by tying or with clamps. (9) Ensure   continuous   lacing   is   not   used, except in panels and junction boxes where this practice is   optional.      Lacing   installed   in   this   manner   outside junction   boxes   shall   be   removed   and   replaced   with individual loops. (10) Ensure  that  tapes  (such  as  friction  tape) which will dry out in service, produce chemical reactions with wire or cable insulation, or absorb moisture, are not used. (11) Ensure  minimum  use  of  insulating  tubing is   made   when   used   to   protect   wire   and   cable   from abrasion,     chafing,     exposure     to     fluids,     and     other conditions  which  could  affect  cable  insulation.    Use  of insulating    tubing    for    support    of    wires    and    cables prohibited. (12) Do   not   use   moisture-absorbent   material as fill for clamps or adapters. (13) Check  that  wires  and  cables  are  not  tied or fastened together in conduit or insulating tubing. (14) Check  that  cable  supports  do  not  restrict the wires or cables in such a manner as to interfere with operation of equipment shock mounts. 3-1