Fuel tanks must have facilities for the inspec-
AIRFRAME FUEL SYSTEM
tion and repair of the tank. This requirement is
met by installing access panels in the fuselage and
Airframe fuel system maintenance is the
wings. Fuel tanks must be equipped with sump
responsibility of more than one work center. For
and drains to collect sediment and water. The
instance, ADs remove and install bladder and self-
construction of the tank must be such that any
sealing fuel cells. Personnel of the AM rating
hazardous quantity of water in the tank will drain
perform the repairs on integral tanks. Personnel
to the sump, so the water can be drained from
from the AO rating usually help in the installa-
the fuel tank. The AD should be familiar with the
tion and removal of external tanks (drop tanks).
different types of fuel tank/cell construction as
To maintain the aircraft fuel system pertaining
described in the following paragraphs.
to the AD rating, you must be familiar with the
aircraft fuel system as well as the engine fuel
system.
Self-Sealing Fuel Cells
To meet the particular needs of the various
types of aircraft, fuel tanks vary in size, shape,
A self-sealing cell is a fuel container that
construction, and location. Sometimes a fuel tank
automatically seals small holes or damage caused
is an integral part of a wing. Most often fuel tanks
during combat operations. A self-sealing cell is
are separate units, configured to the aircraft
not bulletproof, merely puncture sealing. As
design and mission.
illustrated in figure 4-4, the bullet penetrates the
outside wall of the cell, and the sticky, elastic
FUEL TANK CONSTRUCTION
sealing material surrounds the bullet. As the bullet
passes through the cell wall into the cell, the
The material selected for the construction of
sealant springs together quickly and closes the
a particular fuel tank depends upon the type of
hole. Now some of the fuel in the tank comes in
aircraft and its mission. Fuel tanks and the fuel
contact with the sealant and makes it swell,
system in general are made of materials that will
completing the seal. In this application, the
not react chemically with any fuels. Fuel tanks
natural stickiness of rubber and the basic qualities
that are an integral part of the wing are of the
of rubber and petroleum seal the hole. This sealing
same material as the wing. The tank's seams are
action reduces the fire hazard brought about by
sealed with fuelproof sealing compound. Other
leaking fuel. It keeps the aircraft's fuel intact so
fuel tanks may be synthetic rubber, or self-sealing
the aircraft may continue operating and return to
cells or bladder-type cells that fit into cavities in
its base.
the wing or fuselage of the aircraft.
Figure 4-4.-Bullet sealing action.
4-10
