specifies required torque values and refers to the
Apply talc or other suitable powder to the
applicable bolt torque sequence for securing the
outer surface of the cell and the cell cavity to make
part.
it easier to move the cell into position.
If necessary, collapse or fold the cell as
required, and secure it with webbed straps. The
Testing
cell should be warmed to room temperature.
When applying straps, place them and the buckles
When a new or repaired fuel cell is installed
so they are easily accessible after the cell is
in an aircraft, it should be tested for possible leaks
installed.
before it is filled with fuel. The air pressure test
Guide the fuel cell into the cavity, making sure
is the best method of determining if any leaks
it is installed in the right direction. Wooden
exist. This test consists of applying air pressure
paddles with rounded edges may be used to guide
to a sealed cell and checking for the existence of
the cell into the cavity; never use tools with sharp
leaks with a mercury manometer. Further details
edges or points. If any binding occurs, determine
on this type of testing can be found in the specific
the trouble and remedy it before damage is caused
aircraft MIM.
to the fuel cell. Be very careful that protruding
fittings are not damaged.
Remove straps if cell was collapsed; then check
FUEL SYSTEM PART MAINTENANCE
the interior of the cell to make certain that no tools
or foreign materials were left inside.
The maintenance of the aircraft and engine
Install all fittings and components. New seals
fuel system is primarily the responsibility of the
and gaskets must be used.
AD rating. Besides fuel cell repairs, some of these
maintenance tasks that are the responsibility of
NOTE: The use of any sealing compounds
the AD are discussed in the following paragraphs.
on rubber fuel cell fittings is prohibited.
These tasks include inspecting, cleaning, replacing
Sealing compounds may be used only on
fuel parts, and the rigging and adjusting of various
connections when the adjoining surfaces
fuel system controls.
are metal.
Torquing Requirements
Fuel System Component Inspection
One of the main causes of fuel leaks is
Periodically, the entire fuel system must be
improper torquing of bolts used to secure fuel cell
inspected for wear, damage, and leaks. Fuel
access covers, access plates, and cell fittings. Over-
system parts must be inspected for security of
torquing or improper torquing sequence causes
mounting, leaks, and loose connections. Main-
excessive rubber cold flow, warps fitting plates,
tenance should be limited to such items as the
and, in some cases, breaks the metal insert in fuel
tightening of connections to eliminate leaks and
cell fittings. It is important that torquing be
the replacement of defective units. Repairs
performed properly.
involving the disassembly of units are made at
Before the bolts are installed, threads should
overhaul activities.
be inspected for burrs or other defects that could
The entire system should be checked for wear,
damage cell fitting inserts or give incorrect torque
damage, and leaks. All units must be securely
readings. Threaded cell fittings should be in-
mounted and all connections tight and properly
spected to ensure that they are not filled with rust-
safetied. Boost pumps should be used to buildup
preventive compound or dirt. Presence of such
pressure to check for leaks.
foreign material will result in incorrect torque
values.
Pumps
All bolts should be fully installed fingertight
before they are torqued. Bolts should be of proper
The boost pump should be checked period-
length. A bolt that is short will not safely engage
ically for proper operation and correct pressure
the mated part; one that is too long will bottom
output. The pump assemblies must be checked for
out, giving incorrect torque values and causing
leaks, the condition of the fuel, and the condition
leaks.
of the electrical connections. The drain lines must
Each work package (WP) that requires
be free of traps, bends, and restrictions.
removal and installation of a fuel cell access cover
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