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TM 55-2915-335-30&P
1-7. Location and Description of Major Components.
a. Pump cartridge: Model 2C27-3 pump cartridge is a
removable, rotary pump module which houses the pump
motor and impeller. Pump cartridge (1) provides the
pumping action for the fuel boost pump assembly.
b. Pump housing Pump housing assembly (2) is a
receptacle for the boost pump cartridge. The pump hous-
ing includes a system of ports and valves which control
fuel flow to and from the cartridge. The pump housing
also includes a mounting flange which bolts to the bot-
tom of the aircraft fuel tank Together, the pump
cartridge and housing form the fuel boost pump as-
sembly, Model 1C64-1.
c. Pump motor: Pump motor (3) is a permanent-
magnet type DC motor. The motor includes two sets of
brushes and a wet-running armature. Motor cooling and
lubrication is provided by fuel circulating through the
motor chamber.
d. Impeller: A shrouded vane-type centrifugal impel-
ler (4) is housed in the pump cartridge. The impeller is
loose fitted over the end of the motor drive shaft. The
impeller includes an inlet port with a flat seal surface.
During pump operation, the impeller serves as one-half
of a fluid seal in the pumping chamber.
1-8. Differences Between Models.
a. There are two versions of the fuel pump cartridge
in use. Both versions carry the same model number,
2C27-3. The differences in the two versions are between
the impellers and armature drive shafts.
b. The “early version” pumps use a square drive key
that engages slots in the impeller and motor shaft. The
“late version” pumps use a D-drive design. A flat on the
shaft fits into a “D” shaped drive boss on the impeller.
The late version motor does not need a square drive key
to turn the impeller.
c. The early version cartridge is now obsolete. If
either the early version armature or impeller needs to be
replaced, both parts must be ordered. The replacement
parts will be the late version, D-drive type. All other
pump components are similar.
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