There are two drain valves in each tank, one aft and
one forward. The forward valve is a sump drain. The aft
valve is a sump drain and is open to the vent system.
The vent system in each tank is made up of tubes and
two vent boxes. The system allows outside air to enter
and exit the fuel cell during refueling and fuel usage.
The system also prevents fuel from spilling in the event
of a rollover.
Fuel Quantity Probes
Each fuel subsystem has a fuel quantity indicating
system. Five tank quantity transmitter probes (one in
each auxiliary tank and three in the main tank) provide
input to the indicating system . The fuel quantity signal
is directed through a seven position switch to a fuel
quantity indicator on the center instrument panel. The
selector enables the operator to read fuel quantity in
each of the six tanks individually, or to read the total fuel
quantity. Probe support cups, located on the bottom of
the cell, prevent excessive movement of the fuel probes.