only and require installation of the couplings and
continuity wire.
One end has a male coupling and the other end
has a swivel-type female coupling (fig. 5-13). Leakage
between the couplings is prevented by an O-ring in
the female coupling. Both couplings are machined to
receive the nylon spiders that act as non-conducting
supports for connecting the continuity wire. The con-
tinuity wire runs through the hose and is slightly
longer than the hose, to allow for hose stretching.
New hoses and hoses that were out of service for
a long time must be cured (pickled) before being
placed in service. Use the following procedure:
NOTE
Some new hoses manufactured according to
Mil-H-17902 do not require pickling. How-ever,
they must still be flushed and tested prior to
use.
1. Flush the hose with 100 gallons of fuel.
2. Cap one end and elevate the hose.
3. Fill the hose, cap it and let it stand for at least
1 week.
4. Drain the hose and observe drainage for
discoloration. (If discoloration is observed, repeat
steps 1 through 3.
5. Test the fuel with the CFD. (Should be less
than 10 mg/1.)
6. Install the hose and flush until acceptable fuel
is sampled. (Less than 2 mg/1.)
Because of their environment, fuel hoses are sub-
jected to severe wear and tear. They should be in-
spected during each use for superficial cuts, worn
areas or bubbles in the hose, deep cuts that expose
the wire reinforcement or inner layer wrapping, and
leaky couplings.
If any of the above is observed, notify the flight
deck supervisor, flight deck control, and flight deck
repair immediately.
You can prolong the useful life of fuel hoses by
not twisting or kinking a hose, not rolling a twisted
or kinked hose up on its reel, and not allowing
aircraft, tractors. or other rolling stock to run over
the hoses. New fuel hoses are hydrostatically tested
before being placed in-service, and in-service hoses
are hydrostatically tested annually. In accordance
with PMS requirements, fuel hoses are tested at 1 1/2
times their system operating pressure.
If a hose is found to be damaged near an end
coupling but otherwise usable, it may be salvaged by
cutting the damaged area off. This is known as “cut-
ting back” a hose. To cut back a fuel hose, do the
following:
1. Disconnect and remove the spiders and conti-
nuity wire from the hose.
2. Remove the coupling from the damaged end.
a. Unscrew the external taper sleeve from
the coupling end and slide it down past the damaged
area.
Figure 5-13.—Fuel hose couplings.
5-12
