is to insert the defueling suction hose into the tank
through the tank fill opening. For total defueling,
defuel through the aircraft pressure fueling adapter.
The discharge hose from the defueling unit is
connected to the fill connection through a special
Electrical continuity is a firm requirement for all
aircraft refueling stations. Electrical continuity must
be present and maintained to ensure personnel
safety, equipment protection, and efficient fueling
With electrical continuity present, the nozzleman
fueling the aircraft has immediate control of fuel
flow. This is essential to prevent fuel spills and
possible accidents during aircraft refueling. Electrical
continuity is present when wires are provided and
switches are set to allow an electrical current to flow
away from the controller and back to it through a
solid metallic path.
Now, lets follow the continuity circuit (fig. 5-17).
Starting the defuel pump applies power to the solid
state relay, but nothing happens, because the circuit
is broken. Make sure your ground wire to the deck is
grounded to metal. Then hook it to the aircraft.
Remove the dust cover and connect the nozzle. Flip
the switch in the quick-disconnect housing to ON,
which closes the circuit. The ground then goes back
through the spiders in the quick-disconnect coupling
to the wire in the hose. From there, it goes back to
Figure 5-17.Electrical continuity control for the Cla-Val fueling station.