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Operation
Figure 7-7 illustrates operation of the fuel
system in its simplest form. Initial fuel pres-
sure is supplied by the collector tank standby
pump and later by the main ejector through the
open firewall shutoff valve to the LP engine-
driven pump.
The LP pump increases fuel pressure and di-
rects fuel through the heat exchanger and fil-
ter and to the dual-element HP fuel pump. The
#1 HP element produces the high fuel pressure
required by the FCU. The # 2 HP element sup-
plies the motive flow for main and scavenge
ejector operation. The metering section of the
FCU, in response to the computing section
signals, meters fuel through the flowmeter to
the fuel manifold. From the fuel manifold,
fuel is supplied in precisely equal amounts
through the 18 injectors in the combustor.
During this operation, the variable-geometry
section of the FCU, operating in response to
inputs representing N
discharge pressure, directs fuel pressure to
the variable-geometry actuators to position
the inlet guide vanes and stator to produce a
safe surge margin across the compressor. At
the same time, guide vane and stator position
is fed back to the FCU.
NOTE
When the engine is static, the guide
vanes and stators are at their design
maximum closed position. As the en-
gine starts, the guide vanes' and sta-
tors' position will change until, at
high power setting, both the guide
vanes and stators will be at the design
full open position permitting maxi-
mum airflow through the core engine.
IGNITION SYSTEM
General
The CF34-3A1 series engine has a dual high-
energy, capacitor discharge type ignition.
rpm and compressor
2
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
CL-600-2B16 PILOT TRAINING MANUAL
The ignition system for each engine consists
of an ignitor plug A and an ignitor plug B in
the combustor with each ignitor powered
through its own exciter.
Operation of either ignitor is sufficient to pro-
vide for a normal engine start. The ignitor cir-
cuits for each engine are identified as "ignition
A" and "ignition B."
Ignition Modes
The ignition system has four modes, as follows:
1. Ground start ignition
2. In-flight ignition
3. Continuous ignition
4. Auto (stall) protection ignition
Ground Start Ignition
The ground start ignition is integrated with the
engine start system from initiation of start to
the termination of start at 55% N
Either ignition A or ignition B, or both, may
be armed for operation during a ground start
cycle. It is recommended, however, that only
one ignition circuit be armed to prolong igni-
tion plug life.
Control and Indication
Ignition control and indication is provided on
the start and ignition control panel (Figure 7-
8) located on the overhead panel. Two split-
legend switchlights are used to arm A and/or
B ignition circuits for ground starting. Push-
ing either switchlight will illuminate the leg-
end IGN A or IGN B. This indicates that the
selected system is armed to its associated en-
gine START switchlight (Figure 7-8).
Pushing a START switchlight will illuminate
the green START legend and, simultaneously,
the white ON legend of the selected ignition
switchlight, indicating that power is being ap-
plied to the selected ignition exciter. Ignition
will continue until the start cycle is terminated.
Lt é e
Lt d.
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CL 601-3R 7-11
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