Figure 4-40.—Types of JP-5 tanks.
tank is at the fourth deck level, and the bottom is the
shell of the ship. There are an equal number of port
and starboard wing tanks in the forward group and
in the after group. Each port tank has an identical
twin of the same shape and capacity located directly
opposite on the starboard side. These twins are
operated as a unit; that is, they are filled and emptied
as if they were one tank, to preserve the list and trim
of the ship.
Deep centerline tanks referred to here were the
original AvGas tanks on CVs that were converted to
JP-5 tanks. Normally, all forward tanks and the after
port tanks were converted. The cofferdams for the
converted tanks are either filled with fresh water or
used as service or storage tanks.
Seagoing vessels have two bottoms: a bottom and
an inner bottom. The space between double bottoms
is divided into many watertight compartments, which
are used for storage of fuel, water, or ballast. These
are called double-bottom tanks. The bottom of these
tanks is the bottom or outer shell of the ship. The top
of these tanks is the inner bottom, which is also the
deck of the bilge. Double-bottom tanks are, by
necessity, shallow tanks.
Peak tanks are deep tanks, which are located in
the extreme bow and stem of the ship below the
waterline. Only the bow tanks are used for JP-5
storage presently. The shell of the ship forms two
sides and the bottom of each peak tank.
Fuel tanks, like all compartments aboard ship,
are numbered to identify their location. Each tank
has its own number. The first number indicates the
deck level, the second indicates the frame, and the
third indicates the tank’s position in relation to the
ship’s centerline. Knowing the location of the tanks is
a tremendous asset in learning your ship’s fuel
system. It will also help you locate the sounding caps
for each tank’s sounding tube. Generally, the cap will
be one or two decks directly above the tank it serves.
Every sounding cap is marked with its tank number.
Sounding caps are X-ray fittings and must be
replaced tightly after each use.
JP-5 tanks are designed and constructed to fulfill
specific purposes and are classified under two major
categories: STORAGE and SERVICE.
A storage tank is any tank used for the bulk
storage of JP-5. Any wing, deep centerline, double-
bottom, or peak tank can be used for bulk storage. A
service tank is any tank used for storage of JP-5
suitable for issue to aircraft. The JP-5 in a service
tank has been passed through either a filter or a
centrifugal purifier before being pumped into the
service tank. Generally, only wing or deep centerline
tanks are used for this purpose. Service tanks have
but one purpose: servicing aircraft. But storage tanks
can be used for several purposes. The designation of
each tank indicates purpose of that tank.
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