Selector Valves.-- In the continuous-flow
identified by the bright wire braid outer cover with
system, selector valves are not used for tank-to-
red markings. These markings are repeated
engine selection during normal operation.
6 inches apart.
However, in many installations there are selector
This hose is designed for aircraft power plant
valves to enable the pilot or mechanic to control
and airframe fuel and oil lines. It is widely used
the fuel flow for special purposes. This includes
in jet engines. It is flexible, lightweight, and has
fuel integrity checks, shutting off fuel to the
t h e ability to withstand high operating
engine, bypassing fuel components to allow
manual operations in emergency conditions, and
prime consideration. This hose may be used in
cross-feeding fuel to different tanks or engines to
prevent an unbalanced fuel load.
The fitting on this type of hose uses a lip-seal
FUEL LINES AND FITTINGS.-- The fuel
principle, instead of compression, to effect a fluid
lines between the various tanks and between the
seal. This lip-seal is formed during assembly by
tanks and the engine-driven pump are of the
a sharp knifelike spur, which cuts an annular flap
conventional type. They consist of metal tubing
in the hose inner tube. Fitting retention against
or flexible hose. There are drain cocks at low
blowoff is affected by the cutting action of the
spur. This separates the wire braid, which is then
points in the lines so that any water that collects
at these locations may be drained. A quick-
gripped between the nipple and the socket. These
disconnect fitting is often installed in the main fuel
fittings must be marked with a painted stripe to
line to the engine. This fitting permits quick
detect hose pushout after assembly or proof test.
disconnection of the main fuel line when an engine
change is performed.
Rigid Tubing.-- The majority of rigid tubing
The line connecting the various fuel system
used in naval aircraft is manufactured from
units installed on the engine are made of either
aluminum. However, exposed lines and lines
metal tubing or flexible hose. Since these lines
subject to abrasion or intense heat are made of
and fittings must withstand the high pressures
stainless steel. Therefore, you will be concerned
encountered on the discharge side of the engine-
more with stainless steel lines. Whenever an
driven fuel pump, special types are used.
engine fuel line requires replacement, the normal
procedure is to obtain from supply a preformed
Hose Assemblies.-- The
line with fittings attached. If a line must be
lightweight engine hose assembly is designed for
manufactured locally and installed on an engine
continuous operating temperatures of 40°
or component, the original line must be duplicated
to +300°F. The inner tube is seamless and is of
as exact as possible.
a specially formulated synthetic compound. The
reinforcement and cover are of stainless steel wire
Figures 4-12 and 4-13 show a few of the
braid and consist of a partial inner braid and a
correct and incorrect methods of installing metal
full-coverage outer braid. This hose can be
tubing and flexible hose.
Figure 4-12.-Correct and incorrect methods of installing tubing.