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Fuel Filter
A bypass fuel filter removes solids from the
fuel. A red pop-out bypass indicator is pro-
vided, as well as a differential pressure switch.
The switch will illuminate an amber FILTER
light (Annunciator Panel Section) on the fuel
control panel and the appropriate master cau-
tion system whenever the pressure differential
across the filter exceeds a preset value. It is
from the fuel filter that fuel temperature is
sensed and displayed on the temperature in-
dicator on the fuel control panel.
Fuel Control Unit (FCU)
The fuel control unit is an engine-driven hy-
dromechanical-electronic unit that has a me-
tering section and a computing section. The
metering section includes a mechanical gov-
ernor, a fuel metering valve, a bypass valve,
a pressurizing valve, a thrust lever-operated
shutoff valve, and an electronic control unit
(ECU) for fan rpm control.
The computing section of the FCU contains re-
lief valves and servos to sense engine param-
eters such as rpm (N
2
pressure (P
), compressor inlet temperature
3
(T
C), and the position of the variable-ge-
2
ometry system. An amplifier (ECU) operates
a torque motor to control fan rpm (N
The primary function of the FCU is to control
core engine rpm (N
) as a function of thrust
2
lever position. In addition, the FCU modulates
fuel flow to control fan rpm (N
amplifier (ECU) and the torque motor on the
FCU. (See also "Engine Speed Control and
APR Systems" in this chapter.) Engine accel-
eration and deceleration are controlled by the
FCU, based on internal core pressure (P
and inlet temperature (T
The FCU also controls the variable-geometry
system as a function of core engine N
compressor inlet temperature (T
The FCU has a fail-safe schedule in the event of
loss of T
C input. In this case, the variable-ge-
2
ometry and the acceleration schedules will revert
to a fixed temperature reference. If high thrust
), compressor discharge
).
1
) through the
1
C).
2
rpm and
2
C).
2
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
CL-600-2B16 PILOT TRAINING MANUAL
is set at the time of failure, a minor decrease in
thrust may result. If failure occurs at idle thrust,
possible compressor damage can result if an at-
tempt is made to accelerate the engine.
Core engine overspeed in limited three ways:
(1) the N
governor in the FCU, (2) the com-
2
puter section (therefore, if the FCU governor
fails, N
will be limited to less than maxi-
2
mum allowable transient rpm if the comput-
ing section is operational), and (3) if the
computer or the metering valve servo fails, a
bypass valve will open and reduce fuel flow
to the combustor.
The fan rpm control section of the FCU lim-
its fan rpm as a function of thrust lever posi-
tion (PLA) at power settings representing
takeoff, climb, and cruise. In order to minimize
the thrust lever adjustment during climb, the
fan rpm schedule is biased as a function of fan
inlet temperature (T
thrust producer and fan rpm is used to set
thrust. Fan rpm of both engines should be
matched when the thrust levers are aligned.
Fuel Flow Transmitter
A fuel flow transmitter is located in the me-
tered fuel line from the FCU to provide a cock-
pit indication of fuel flow.
#1 Fuel Manifold
The fuel manifold consists of two separate
180° halves which encircle the combustion
chamber frame. Integral with the continuous
ring are eighteen fuel injector hoses which
connect to eighteen fuel injectors. The fuel in-
jectors are dual-orifice injectors. Each injec-
tor has two independent fuel flow passages, a
),
primary path for startup and idle conditions and
3
a secondary path for above idle and higher
power settings. This system allows better fuel
distribution and atomization during entire
range of power settings.
#2 Fuel Drains
Fuel drains from the variable geometry actu-
ators, the FCU, and the combustor and turbine
sections are routed overboard.
Lt é e
Lt d.
). The fan is the primary
2
CL 601-3R 7-9
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