disappears at the bottom, air is present. If the cloud
disappears at the top, water is present. If the cloud does
not begin clearing in a few minutes, it is due to entrained
water or very fine particulate matter. Do NOT use any
fuel containing a cloud that does not disappear in a few
minutes after it is drawn or use a fuel containing any
visible water to fuel an aircraft.
3. The third check should be for sediment. Swirl
the sample so a vortex is formed. All sediment that has
settled accumulates on the bottom of the bottle directly
beneath the vortex. At the most, the total sediment
should be only a point or spot of silt. In a quart sample,
the sediment should be no more than a slight smudge if
picked up on a fingertip.
Coarse contamination can be detected visually.
Sediment in the fuel is visible when the particles are
40 microns or larger. Groups of particles less than 5
microns in size may be seen in the fuel when viewed
at a right angle to a strong light. When a fuel sample
is being inspected, it should be swirled and allowed to
settle for a few moments. The coarse particles settle to
the bottom center of the bottle and collect in a group.
Any sediment that can be seen is too much for aircraft
The AEL Free Water Detector should be used to
determine the presence of free water above the allow-
able limit (for aircraft) of 5 ppm. Free water at this level
of contamination mayor may not be visible to the naked
Fuel that is contaminated by commingling with
another petroleum product is hard to detect visually.
In gasoline, if the percentage of the other petroleum is
fairly high, there may be a color change. JP-5 contami-
nated by JP-4, or vice versa, can be detected by a test
for flash point and a laboratory test for distillation.
If any contamination is discovered during the vis-
ual inspection procedure, stop the fueling operation
immediately and notify the pilot of the aircraft, the
fuels officer, or other designated person in charge as
to the condition of the fuel.
A contaminated sample should be suitably tagged
and retained until it is determined that a laboratory
analysis of the sample is not required. When any
contamination is found, another sample should be
taken, preferably in a new sample container. Take care
to ensure that the container is thoroughly clean before
drawing the sample. Once contamination is found and
the system placed out of use, a check must be mad
for the source and cause of the contamination and the
cause corrected before the system is placed in use
again. The type of contamination discovered usually
gives a clue to the source and cause. Some of these
indications are as follows:
1. Mixed or commingled fuelsThe valve or
blank flange is open between two different systems or
there is a leak through a bulkhead where two tanks
containing different fuels are adjacent.
2. WaterThe filter/separator elements are rup-
tured or contaminated. Large amounts of water also
indicate that the filter/separator float control valve was
not operating and water stripping operations for the
service tanks were inadequately performed.
3. Sediment and microbiological growthThe fil-
ter/separator elements are ruptured or contaminated.
Large amounts of sediment or microbiological growth
also would indicate that the storage tanks and service
tanks need cleaning.
CONTAMINATED FUEL DETECTING
The equipment used in the lab is portable but only
to the extent that it may be earned from one area to
another. You cannot carry it around with you for daily
use. It is better to describe it as movable even though
PMS electrical safety checks require it to be listed as
A good fuels lab has the following facilities: good
ventilation, hot and cold water to wash bottles, and a
bottle drying rack. Bottle drying racks can be bought
commercially, but most are constructed locally. See
The combined contaminated fuel detector (CCFD)
is a single unit that contains both the AEL Mk I and
AEL Mk III. Many stations and ships have both the
CCFD and the single units. The AEL Mk II is the same
as the Mk I except it has a carrying handle,
The AEL Mk I and Mk II are used to measure
water contamination, and the AEL Mk III is used for
sediment detection. The closed cup flash-point tester
is used to determine the flash point of jet fuels. The
flash-point tester is not to be used to test gasoline
products. The refractometer indicates the amount of