TM 1-1520-240-10
2-4-5
2-4-6). The switches are used to test the automatic shut-
off features in each tank and to stop refueling when the
desired fuel level is attained in each or all tanks. Six of the
seven switched are connected to fuel level control valves
in a specific tank. The seventh switch, labeled ALL TEST,
is electrically connected to the fuel level control valves in
all six tanks. Setting any of the six switches to PRI OFF
or SEC OFF raises the corresponding primary or secon-
dary float in the fuel level control valve. This action simu-
lates a high fuel level and causes the fuel shutoff valve
in that tank to close. Setting the ALL TEST switch to PRI
OFF or SEC OFF raises the corresponding float in all six
tanks and shuts off the fuel flow into all tanks simulta-
neously.
2-4-16. REFUEL VALVE POSN Indicating Lights.
The two amber PRESS-TO-TEST REFUEL VALVE
POSN (position) lights (fig. 2-4-6) indicates the status of
the two refueling valves in the pressure refueling system.
The valves are normally closed and prevent fuel feed-
back into the aft auxiliary tanks when the aft tank pumps
are operating. While pressure refueling the valves are
opened and allow fuel flow from the refueling system into
the aft tank.
The valves are controlled by the refueling station PWR
ON switch. When the switch is ON, the valves are
opened and the indicating lights will illuminate momen-
tarily indicating valve transition from close to open. Con-
versely, when the switch is OFF, the valves are closed
and the indicating lights will illuminate momentarily indi-
cating valve transition from open to close. A continuously
illuminated light, with the switch at OFF, indicates the
associated valve is opened and the fuel in the tank will
not be available.
