TM 1-1500-204-23-3 CHAPTER 2 FUEL SYSTEMS 2-1.    General.      The   fuel   system   supplies   fuel   to   the carburetor  or  fuel  control  under  all  conditions  of  ground and   air   operation.      Identification,   contamination,   and general   maintenance   practices   will   be   covered   in   this chapter. 2-2.    Safety  Precautions  and  Procedures.    The  safety precautions   and   procedures   below   are   only   minimum requirements  for  average  conditions.    All  personnel  who are  required  to  service,  maintain,  or  repair  fuel  systems should observe the precautions described in the following paragraphs. a. Fuel  Lines  and  Drains.    Keep  all  fuel  vents  and drains clean and open. b. Tools.    Use  only  sparkproof  hand  or  air  power tools in the maintenance of fuel systems. c. Tool  Boxes.    Rubber  wheeled  tool  boxes  inside the  fuel  cell  repair  area  shall  be  bonded  to  the aircraft and grounded.  Tool boxes, except those mounted  on  rubber  wheels,  shall  remain  outside the   fuel   cell   repair   area.      Tools   required   to perform maintenance shall be hand-carried to the aircraft in nonmetallic containers, such as cardboard   boxes   or   canvas   bags.      Tool   boxes locked and secured in storage racks need not be removed  from  the  fuel  cell  repair  area  providing they remain locked and in the storage racks. d. Work Stands.  All work stands shall be equipped with  a  personnel  static  discharge  plate  made  of copper, zinc or zinc coated material, or other non- oxidizing  material.    The  plate  shall  be  welded  to the    handrail,    at    entrance    to    the    stand,    so personnel can contact it before coming in contact with   the   aircraft.      The   plate   shall   be   marked "PERSONNEL    STATIC    DISCHARGE    PLATE." Work  stands  inside  the  fuel  cell  repair  area  shall be  bonded  to  the  aircraft  or  grounded.    Properly installed  and  maintained  ground  reels  located  on the work stand bases can be used. WARNING Plastic    or    polyethylene    buckets shall  not  be  used  for  collecting  or storing    fuel.        They    cannot    be grounded. e. Drain  Containers.    Approved  metal  containers  or bowsers   shall   be   used   to   catch   running   fuel. When  metal  containers  are  used,  they  shall  be bonded to the aircraft and grounded.  When not in use,  they  shall  be  grounded  at  all  times.    Only approved containers shall be used to drain small amounts of residual fuel. CAUTION Personnel  approaching  an  aircraft for  fuel  system  maintenance  shall ground themselves to remove static electricity. f. Personnel.    Before  entering  a  fuel  system  repair area   all   personnel   shall   dispose   of   all   lighted cigarettes,   cigars,   pipes,   and   any   spark/flame producing device, such as matches or lighters on their person. 2-3.      Fuel   Identification.      Turbine   fuel   and   Aviation Gasoline (AVGAS) identification and volatility are explained     in     the     following     paragraphs.          Additional information can be found in TB 55-9150-200-24. a. Turbine   Fuels.      Two   types   of   jet   fuel   are   in common  use.    Jet  A  (JP-5)  is  a  heavy  kerosene having   a   higher   flash   point   and   lower   freezing point  than  most  kerosenes.    It  has  a  very  low vapor pressure, so there is little loss of fuel from evaporation  or  boil  off  at  higher  altitudes.    Jet  B (JP-4) is a blend of gasoline and kerosene.  JP-4 is   the   Army   standard   fuel   for   turbine   engines. The difference in the specific gravity of the fuels may require fuel control adjustments.  Therefore, the fuels cannot always be considered interchangeable.  The critical characteristics of jet fuels JP-4 and JP-5 are shown in table 2-1. (1) Turbine fuel identification.  Because turbine fuels  are  not  dyed,  there  is  no  on-sight  identification  for them.    They  range  in  color  from  a  colorless  liquid  to  a straw-colored   liquid,   depending   on   age   or   the   crude petroleum source. (2) Turbine   fuel   volatility.      One   of   the   most important characteristics of turbine fuel is its volatility.  A high volatility is desirable to aid cold-weather starting and to   make   aerial   restarts   easier   and   more   sure.      Low volatility is desirable to reduce the possibility of vapor lock and to reduce fuel loss by evaporation.  Figure 2-1 shows the    vaporization    characteristics    of    aviation    fuels    at atmospheric pressure. 2-1