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ENGINE-DRIVEN PUMPS
Each two-stage engine-driven fuel pump is a
single unit containing two pumps mounted in
piggyback fashion. The first stage is a cen-
trifugal, low-pressure pump which receives
fuel from the main ejector and supplies it to
the engine and the second stage, or high-pres-
sure side, of the pump. This second stage uses
a positive-displacement pump to supply high-
pressure motive flow fuel to the main and
scavenge ejectors (see Figure 5-2).
Operation of the engine fuel system is dis-
cussed in Chapter 7, "Powerplant."
CROSSFLOW VALVE
Should a main tank fuel imbalance occur in
flight for any reason, it can be corrected by
opening the crossflow valve (see Figure 5-2)
which connects both main tanks and both col-
lector tanks. Balance is achieved through grav-
ity flow only. To avoid a serious imbalance
which might occur if the wings are not level,
the crossflow should not be left open when the
airplane is on the ground.
POWERED CROSSFEED VALVE
When depressing the LEFT TO RIGHT or
RIGHT TO LEFT switchlight, the associated
powered crossfeed shutoff valve opens to allow
fuel flow, by gravity, into the auxiliary fuel
tank. Fuel is then transferred to the opposite
tank while a quantity is returned to its origi-
nal tank by the transfer ejectors when in flight
or the fuel boost pumps via the transfer ejec-
tors when on the ground.
NOTE
Maximum imbalance is 800 pounds.
5-6 CL 601-3R
CL-600-2B16 PILOT TRAINING MANUAL
APU FUEL SYSTEM
The APU is normally supplied with fuel from
the right main tank by an electric fuel pump.
The pump is identical to the standby electric
pumps described previously.
The APU fuel pump operates whenever it is se-
lected on by a switch on the APU control
panel. Fuel in excess of APU requirements is
routed back to the right main tank through a
fuel-oil heat exchanger which cools the APU
generator adapter oil (Figure 5-5). Operation
of the APU is discussed in Chapter 6, "Aux-
iliary Power Unit."
The APU fuel feed line is fitted with two APU
fuel shutoff valves that are synchronized and
controlled by the APU electronic control unit.
To ensure uninterrupted operation of the APU
during brief moments of negative G flight or
in case of APU fuel pump failure, fuel can be
supplied from the left engine feed line to the
APU (Figure 5-6). This line has a differential
pressure, one-way check valve which opens
whenever the main APU supply pressure drops
10 psi lower than the pressure in the left en-
gine fuel feed line. Fuel from the left engine
feed line cannot flow to the right tank or to any
heat exchanger because of a check valve in-
stalled in the main feed line.
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
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