energize the pump. When switch is at OFF, the relay
circuits open and power from the No. 1 and No. 2 AC bus
is de-energized thus shutting off the pump. Power is
supplied for these relay circuits by the No. 1 and No. 2 DC
bus through the LH and RH FUEL PUMP CONT - AUX
AFT, MAIN AFT, MAIN FWD, and AUX FWD circuit
breakers on the No. 1 and No. 2 PDP. Power is supplied
to the pumps circuits by the No. 1 and No. 2 AC bus
through the LH and RH FUEL PUMPS - MAIN FWD,
MAIN AFT, AUX FWD, and AUX AFT circuit breakers on
the No. 1 and No. 2 PDP.
AUX PRESS Indicating Lights. Each light is
electrically connected to the forward and aft auxiliary
tank pressure switches. When this indicating light illumi-
nates, it indicates that the fuel pressure in either the
forward or aft auxiliary fuel line is below 10 $ 1 psi. The
auxiliary tank fuel boost pump switches must be at ON to
provide electrical power to the indicating light. The light
intensity can be adjusted by turning the light housing.
Power is supplied to operate the indicating light by the
No. 1 and No. 2 DC bus through the LH or RH Fuel PUMP
CONT AUX FWD & AUX AFT circuit breakers on the No.
1 and No. 2 PDP.
XFEED Switch. The switch electrically operates
two fuel valves in the crossfeed line. The switch has an
OPEN and CLOSE position. When the switch is at
OPEN, power from the No. 1 DC bus opens the fuel
valves through the XFEED CONT circuit breaker on the
No. 1 PDP. When the switch is at CLOSE, electrical pow-
er closes the valves.
2-4-5. Fuel Valves.
There are two engine and two crossfeed fuel valves.
Engine Fuel Valves. One engine fuel valve (fig.
2-4-2) is in the fuel supply line to each engine. The valve
is electrically operated by the FIRE PULL handles and
manually by a lever on the valve. They are located at sta.
498 and labeled FUEL VALVE # 1 ENGINE and FUEL
VALVE # 2 ENGINE.
Crossfeed Fuel Valves. The crossfeed fuel
valves connects the No. 1 and No. 2 engine fuel lines.
When the valve is opened, both engine fuel feed lines are
interconnected and fuel can be supplied from both fuel
tanks to feed either engine or from either tank to feed
both engines. Fuel cannot be transferred between tanks.
The valves are electrically operated by the XFEED
switch on the FUEL CONTR panel or manually by a lever
on the valve. They are labeled FUEL VALVE CROSS-
FEED and located at station 504.
FUEL VALVE WARNING LIGHT. There are two
PRESS-TO-TEST FUEL VALVE WARNING LIGHT next
to each FUEL VALVE CROSS FEED
Figure 2-4-2. Engine Fuel Valves, Sta. 498
and two PRESS-0TO-TEST FUEL VALVE WARNING
LIGHT next to FUEL VALVE # 1 ENGINE and # 2 EN-
GINE (fig. 2-4-3). They indicate the operating condition
of the individual valve and associated circuitry. Power is
supplied to operate the crossfeed FUEL VALVE WARN-
ING LIGHT by the No. 1 DC bus through the XFEED
CONT circuit breaker on the No. 1 PDP. Power is sup-
plied to operate the engine FUEL VALVE WARNING
LIGHT by the DC essential bus through the ENGINE NO.
1 and NO. 2 FUEL SHUT-OFF circuit breakers on the No.
1 and No. 2 PDP.
The following description on when the light will illuminate
is for the XFEED switch. The same result applies to the
engine fuel valves with the FIRE PULL handles.
Each time the XFEED switch is moved from
CLOSE to OPEN or OPEN to CLOSE. After this opera-
tion, the light should extinguish, indicating the crossfeed
valve is synchronized with the switch position.
When a short circuit occurs, causing a signal
to be applied opposite to the valve position. However, the
valve will remain at the position last selected by XFEED
When the crossfeed valve protection relay
fails. The crossfeed valve will remain at the last selected
position and the valve can be operated electrically or
manually, as required.