(4) Fuel crossfeed switch. The fuel crossfeed valve is controlled by a 3-position switch (Fig. 2-25),
located in the fuel management panel, placarded CROSSFEED OFF . During normal light conditions, the switch
is left in the OFF position. During emergency single engine operation, it may become necessary to supply fuel
to the operative engine from the fuel system on the opposite side. The crossfeed system is placarded for fuel
selection with a simpliied diagram on the overhead fuel control panel. STANDBY PUMP switches shall be in
the off position when crossfeeding. A lever lock switch, placarded CROSSFEED , is moved from the center OFF
position to the left or right, depending on direction of fuel low. This opens the crossfeed valve and energizes the
standby pump on the side from which crossfeed is desired. During crossfeed operation with irewall fuel valve
closed, auxiliary tank fuel will not crossfeed. When the crossfeed mode is energized, a green FUEL CROSSFEED
annunciator on the caution/advisory panel will illuminate. Crossfeed system operation is described in Chapter 9.
The crossfeed valve is protected by a 5-ampere circuit breaker placarded CROSSFEED located on the overhead
f. Firewall Shutoff Valves.
Do not use the fuel irewall shutoff valve to shut down an engine, except in an emergency. The
engine-driven high- pressure fuel pump obtains essential lubrication from fuel low. When an engine
is operating, this pump may be severely damaged (during cavitations) if the irewall valve is closed
before the condition lever is moved to the FUEL CUTOFF position.
The fuel system incorporates a fuel line shutoff valve mounted aft of each engine irewall. The irewall shutoff valves
close when the ire extinguisher T handles on the instrument panel are pulled out. The irewall shutoff valves receive
electrical power from the main buses, and also from the hot battery bus which is connected directly to the battery.
The valves are protected by 5-ampere circuit breakers placarded FIREWALL VALVE #1 or #2 on the overhead
circuit breaker panel (Fig. 2-12), and FIREWALL SHUTOFF #1 or #2 on the hot battery bus circuit breaker board.
g. Fuel Tank Sump Drains. A sump drain wrench is provided in the aircraft loose tools to simplify draining a
small amount of fuel from the sump drain.
There are ive sump drains and one ilter drain in each wing (Table 2-3).
(2) An additional drain for the extended range fuel system line extends through the bottom of the wing
center section adjacent to the fuselage. Any time the extended range system is in use, a part of the prelight
inspection would consist-of draining a small amount of fuel from this drain to check for fuel contamination. When-
ever the extended range system is removed from the aircraft and the fuel line is capped off in the fuselage, the
remaining fuel in the line shall be drained.
Fuel Sump Drain Locations
Leading Edge Tank
Outboard of nacelle, underside of wing
Underside of wing, forward of aileron
Firewall Fuel Filter
Underside of cowling forward of irewall
Bottom center of nacelle forward of wheel well
Gravity Feed Line
Aft of wheel well
At wing root, just forward of the lap
Outboard of fuselage on underside of wing center section