d. Uses of Additives to Prevent Mirobiological Growth.
The addition of fuel system icing inhibitor (FSII) has
helped curb microbiological growth.
However, in spite of the effectiveness of FSII, it is still
very important to remove all water from aviation fuel and
aircraft fuel systems.
(1) Oxidation and corrosion inhibitors. In general, ASTM
specifications for jet fuels permit the use of approved
oxidation and corrosion inhibitors and metal deactivators.
However, the quantities and types must be declared and
agreed to by the consumer. Military specifications permit
use of a metal deactivator in either JP-4 orJP-5 fuel and
also permit an approved corrosion inhibitor in JP-4,
provided it is blended into the fuel by the supplier. MIL-T-
5624 presently contains the requirement that both grade
JP-4 and JP-5 contain icing inhibitors. The specification
requires that these inhibitors be added at the refinery to a
minimum percent volume of 0.10 and 0.15 percent
(2) Icing inhibitor. Icing inhibitor conforming to MIL-1-
27686 shall be added to commercial fuel not containing
an icing inhibitor during refueling operations, regardless of
ambient temperatures. The additive provides anti-icing
protection and also functions as a biocide to kill microbial
growths in aircraft fuel systems. The additive (Prist or
equivalent) is not available through the Army Supply
System it is to be procured locally when needed.
Refueling operations shall be accomplished in accordance
with accepted commercial procedures.
(See specific aircraft manuals for any limitations.)
Contamination Prevention. Any time fuel is
transferred, it is susceptible to contamination. The
following paragraphs contain precautions to prevent fuel
Fuel storage. Fuel being pumped into
airpiort storage should pass through a filter-separator.
The filter should meet the requirements of U.S.
Government Specification MIL-F-8508A.
Turbine fuel. Turbine fuels should be
allowed to settle for a period of one hour per foot of depth
of the fuel before being withdrawn for use. This means
that ordinarily more than one storage tank must be
provided for each grade of product.
Storage tanks. Storage tanks should be
checked with litmus paper after each new load of fuel is
received and the fuel has settled. The litmus paper
should remain submerged for a minimum of 15 seconds.
During periods of heavy rain, underground tanks should
be checked with litmus paper more frequently.
Suction lines. Suction lines should be a
minimum of 6 inches from, the bottom of the tank.
Kerosene storage tanks should be equipped with floating
type suction lines. Floating suction does not remove the
bottom product, which may not have settled sufficiently.
It also prevents reintroduction into the fuel of any
contamination at the bottom of the tank. Floating suction
is the only logical way to take full advantage of gravity in
removing water and particulate matter contamination. Its
importance must not be minimized.
Fuel withdrawal. Fuel being withdrawn
from storage should be passed through a filter separator
meeting the specification MIL-F-8508A.
Loading. Great care should be exercised in
loading mobile fuelers to exclude airborne dust and dirt,
rain or other foreign material.
Tanks. To lessen the likelihood of rust and
scale the tanks of mobile fuelers should be constructed of
either stainless steel, nonferrous material or steel coated
with a reliable, inert material.
Filtering. As turbine fuel is being dispensed
into the aircraft from truck or hydrant it should be filtered
to a degree of 5 microns for solid particles and contain no
more than 0.0015 percent of free and entrained water.
Bypass valves around the filter should not be permitted.
(9) Quality control. All the quality control
procedures usually followed in handling
aviation gasoline should be employed.
These include regular and frequent check of
filter-separators; frequent quality check such
as the clear and bright test. and continual
emphasis on cleanliness. Examples: "Don't
let the hose nozzle drag on the apron."
"Keep the dust cap on the nozzle at all times
when nozzle is not in use."
2-5. Fuel System Maintenance. General maintenance
on fuel lines, pumps, sumps, strainers, float switches,
cells, tanks, quick-disconnect couplings, and closed-circuit
refueling receptacles are explained in the following
paragraphs. Fuel system testing and troubleshooting are
also covered. Inspection, removal, and installation are
covered in TM 1-1500-204-23-2.
Fuel Lines. Various fuel tanks and other
components are usually joined together by fuel lines
made of metal, connected where flexibility is necessary,
by lengths of flexible hose. Metal and flexible hose lines
and inspection, removal, and installation of fuel lines on
aircraft are explained in the following paragraphs.