Apu Fuel System - BOMBARDIER Challenger 601-3A 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 with the standby elec-
tric 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 5-8). Operation
o f t h e A P U i s d i s c u s s e d i n C h a p t e r 6 ,
"Auxiliary Power Unit."
STANDBY
PUMPS
FROM
LEFT MAIN
EJECTOR
CENTER TANK
TO LEFT
ENGINE
APU NEGATIVE-G
SHUTOFF VALVE
APU NEGATIVE-G
CHECK VALVE
LEGEND
APU PUMP PRESSURE
MAIN EJECTOR PRESSURE
5-8 CL 601-3A
PRESSURE
SWITCH
APU FUEL FEED
SHUTOFF VALVE
CHECK
VALVE
FUEL CONTROL
UNIT SHUTOFF VALVE
Figure 5-8. APU Fuel System—Normal Operation
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
CL-600-2B16 PILOT TRAINING MANUAL
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 5-9). 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.
RIGHT MAIN TANK
APU
FUEL
PUMP
RESTRICTOR
CHECK
VALVE
FUEL
CONTROL
UNIT
TO PNEUMATIC
SYSTEM
LOAD
CONTROL
VALVE
APU GENERATOR
OIL HEAT
EXCHANGER
L té e
L td .