1.   LOGIC   DIAGRAMS:  Logic  diagrams  in- clude  troubleshooting  logic  charts  (TLCs),  fault  logic diagrams  (FLDs),  fault  isolation  pyramid  charts,  and fault  reference  tables.  The  TLCs  and  the  FLDs  pro- vide   a   simple   yes-or-no,   question-and-answer   ap- proach  to  fault  isolation.  They  are  generally  based  on either  a  ladder  method  or  a  bracket-and-halving  fault- isolation   technique. Ladder  Method:  The  function  is  approached from  its  initiation  or  termination  point  and,  in  succes- sive  steps,  is  checked  to  the  other  end. Bracket-and-Halving   Fault-Isolation   Tech- nique:  The  function  is  checked  at  its  midpoint,  then  at the  midpoint  of  the  half  containing  the  fault,  etc.,  until it  is  isolated. Pyramid  charts  take  an  output  or  terminal  func- tion  (output,  indicator,  etc.)  and  break  it  down  into  its major   subfunctions,   which   are   individually   checked until  the  fault  is  isolated.  Fault  reference  charts  gen- erally  relate  symptoms  to  specific  faults. 2.  FUNCTIONAL  FLOW  DIAGRAMS:  Func- tional   flow   diagrams   include   system   functional   dia- grams,  signal-flow  diagrams,  schematic  diagrams,  and relay-ladder   diagrams.   These   are   frequently   used   in isolating  a  fault  that  was  not  anticipated  by  the  fault logic   material   provided. In  general,  fault  logic  procedures  are  used  more rapidly   by   inexperienced   technicians   than   fictional diagrams  in  isolating  a  specific  fault.  When  used  with flow  diagrams,  fault  logic  procedures  provide  a  means of  teaching  new  or  inexperienced  personnel  effective fault-isolation   techniques.   A   fictional   understanding gained  through  the  use  of  maintenance  documents  is necessary   for   the   development   of   experienced   tech- nicians.   Experienced   technicians   frequently   isolate specific   faults   addressed   in   fault   logic   procedures faster   without   referring   to   procedures.   Their   experi- ence  is  essential  in  isolating  problems  that  have  not been  anticipated  by  logic  procedures. Numerous  approaches  are  possible  in  the  applica- tion  of  fault-isolation  procedures.  The  fact  that  most casualties  occur  within  an  equipment  and  are  cor- rected  by  troubleshooting  on  an  equipment-level  basis leads  to  the  tendency  to  troubleshoot  all  casualties  on an  equipment-level  basis.  It  is  to  be  expected  that  each technician  might  rely  more  heavily  on  certain  trouble- shooting  aids  and  procedures  than  others.  Few  hard- and-fast  rules  apply  to  all  troubleshooting  situations, but  one  rule  that  should  always  be  foremost  is  to  de- termine  the  origin  of  a  fault  as  precisely  as  possible. System  interrelationship  is  such  that  many  casual- ties  can  be  reflected  in  several  areas  as  improper  op- eration   or   fault   indications.   If   each   area   of   each equipment  that  does  not  function  properly  is  checked separately,   the   equipment   downtime   and   correspond- ing  man-hour  use  can  rapidly  increase.  On  the  other hand,   familiarity   with   system   reference   materials, system   fictional   diagrams,   and   fault-isolation   proce- dures  can  lead  logically  and  expeditiously  to  the  spe- cific  area  of  the  fault. All   system   fault   isolation   is   interrelated.   Its effective  use  depends  on  knowing  what  materials  are available,  how  they  are  interrelated,  and  how  to  cross- -reference   between   materials.   The   isolation   materials that  you  will  use  in  fault  isolation  are  the  system  fault indicator   director,   the   system   function   directory,   the system  functional  diagram,  the  fault  analysis  matrix, a  sample  troubleshooting  problem,  and  the  equipment troubleshooting   documentation. System   Fault   Indicator   Directory The  system  fault  indicator  directory  (FID)  facili- tates   entry   into   the   documentation   required   for troubleshooting  a  fault  disclosed  by  a  specific  indica- tor  during  normal  operation.  A  typical  FID  is  shown in  table  1-3.  The  material  in  this  FID  is  grouped  by system   and   further   divided   alphabetically   by   equip- ment,  panel,  and  indicator.  A  complete  listing  of  indi- cators  is  included. 1-11