Purity Proper procedure for minimizing water entering aircraft  fuel is to fill the aircraft fuel tanks immediately after each  The purity of aviation gasoline is compromised most often  by water. Water also settles into the sumps given enough  time. However, water is not removed by the aircraft’s filters  and strainers as easily as solid particles. It can enter the fuel  even when the aircraft is parked on the ramp with the fuel  caps in place. Air in the tank vapor space above the liquid  fuel contains water vapor. Temperature fluctuations cause  the water vapor to condense on the inner surface of the tanks  and settle into the liquid fuel. Eventually, this settles to the  sump, but some can remain in the fuel when the aircraft is  to be flown. Identifying fuel and ensuring the correct fuel is delivered  into storage tanks, fuel trucks, and aircraft fuel tanks is a  process aided by labeling. Decals and markings using the  same colors as the AVGAS colors are used. Delivery trucks  and hoses are marked as are aircraft tank fuel caps and fill  areas. Jet fuel fill hose nozzles are sized too large to fit into  an AVGAS tank fill opening.  Figure 14-8  shows examples  of color-coded fuel labeling. The color of fuel may be referred to in older maintenance  manuals. All grades of jet fuel are colorless or straw colored.  This distinguishes them from AVGAS of any kind that  contains dye of some color. Should AVGAS fuel not be  of a recognizable color, the cause should be investigated.  Some color change may not affect the fuel. Other times, a  color change may be a signal that fuels have been mixed or  contaminated in some way. Do not release an aircraft for  flight with unknown fuel onboard. era. It is available only by special order from refineries and  is also dyed purple in color. The use of filters in the various stages of transfer and storage  of AVGAS removes most foreign sediment from the fuel.  Once in the aircraft fuel tanks, debris should settle into the  fuel tank drain sumps to be removed before flight. Filters and  strainers in the aircraft fuel system can successfully capture  any remaining sediment. Fuel Type and Grade  Color of Fuel  Equipment Control Color  Pipe Banding and Marking  Refueler Decal 82UL AVGAS 100 AVGAS 100LL AVGAS JET A JET A-1 JET B Purple Green Blue Colorless or straw Colorless or straw Colorless or straw AVGAS 82UL AVGAS 100 AVGAS 100LL JET A JET A-1 JET B 82UL AVGAS 100 AVGAS 100LL AVGAS JET A JET A-1 JET B AVGAS 82UL AVGAS 100 AVGAS 100LL JET A JET A-1 JET B Figure 14-8.  Color coded labeling and markings used on fueling equipment. 14-7