SUMMARY OF CHARACTERISTICS
In summary, it is important that you remember the
following characteristics of fuels:
From the standpoint of fire, explosion, and
health, gasolines, JP-4, and JP-8 are extremely hazard-
ous and must be handled with equal caution. JP-5 jet
fuel is safer, with respect to possible explosions and
poisoning. However, the potential hazards of fire from
fuel-soaked rags and waste and of skin blistering from
soaked clothing must not be ignored.
Jet engine fuels and gasolines are designed for
entirely different types of engines. Therefore, the proper
fuel must be used for each type of engine.
LEARNING OBJECTIVES: Describe the prob-
lems caused by fuel contamination. State the
types and limits of fuel contaminants. Describe
the equipment used and explain the correct
operating procedures in testing for fuel con-
The major objective of fuel-handling personnel is
to deliver fuel to aircraft, clean and free of water. The
complex fuel systems of modem aircraft do not func-
tion properly if the fuel is contaminated with dirt, rust,
water, or other foreign matter. Even very small quan-
tities of dirt or solid matter can plug or restrict fuel
metering orifices and accelerate the clogging of fuel
filters. Very small quantities of water are also harmful
since ice may form in aircraft tanks at high altitudes.
Ice affects orifices, controls, and filters like dirt. The
complete stoppage of fuel flow by ice or dirt causes
engine failure, and partial stoppage causes poor engine
PROBLEMS CAUSED BY FUEL
Contaminated fuel has caused aircraft accidents
with a tragic loss of life, loss of valuable aircraft, and
the grounding of entire squadrons. This means that
clean fuel is a LIFE-OR-DEATH matter with aviation
personnel. The lesson has been learned the hard way
by too many, and with fatal results. The time to be-
come fuel conscious is NOW.
Besides being deadly, contaminants can be sneaky.
A certain type of emulsion resulting from the presence
of water and rust particles can stick to the sides of an
aircrafts fuel cells and not be noticed. You can even
drain out a sample of fuel and find no evidence of this
deposit. It can continue to build up and part of it may
wash off and pass through a strainer into a fuel control.
There can be only one result, reduced power and, fi-
nally, engine failure.
Foreign particles so small they cannot be seen with
the naked eye can cause damage in a jet engine. The
fuel control of a jet engine is a masterpiece of engi-
neering and craftsmanship. It automatically regulates
fuel flow to compensate for changes in altitude and
speed. It makes practical the piloting by human beings
of incredibly powerful jet aircraft. But doing these
things requires that the fuel control have precisely
fitted meters and valves. The moving parts within
some of these meters and valves have clearances of
less than 0.005 of an inch. Particles of foreign matter
only slightly larger than this clearance can jam the
valve or prevent it from seating properly. Particles
slightly smaller can stick and build up, or wedge
between the parts. Thus, we must remove particles so
small they can be seen only with a microscope.
UNNECESSARY REPAIR WORK
Fuel carrying water or dirt can cause a great deal of
extra maintenance work. For example, in atypical Navy
engine overhaul shop it became necessary at one time
to completely disassemble every jet engine fuel control
that came into the shop because of the chance of internal
damage. Ordinarily, the controls that had been in use
less than half of their overhaul time could have simply
been bench-checked to verify their performance and
then returned for use on the engine. However, experi-
ence showed that more than 50 percent of the fuel
controls overhauled had failed because of internal cor-
rosion. The cause was water in the fuel. Such extra
repair work is not confined to jet engines. Water in the
fuel also can cause erroneous readings on the aircrafts
fuel quantity gages, which can be exceedingly danger-
ous in flight.
In addition to causing engine failures, fuel contami-
nation can mean serious delays in flight operations.
Normal procedure requires that all aircraft fueled from
a source where contamination is discovered be checked.