air to the compressor of the core engine and the
second path directs air into the fan bypass duct.
The fan functions to accelerate a large air mass
to a moderate velocity through the bypass duct
and contributes approximately 80% of the total
thrust developed by the CF34 engine.
Compressor
The high-pressure (HP) compressor is located
aft of the front frame. This single-spool axial
compressor has 14 stages with a pressure ratio
of 14:1.
The HP compressor supplies air for cooling,
bearing and seal pressurization, hot-point
cooling, and for combustion in the core engine.
In addition, it supplies bleed air for the air-
plane’s pneumatic services.
A variable-geometry system automatically
controls the inlet guide vanes and five variable
stator vanes to maintain a safe surge margin
across the HP compressor. This helps prevent
compressor stall or surges when the engine is
operating in the low-power range or during
rapid acceleration or deceleration.
The variable-geometry system is controlled by
the fuel control unit (FCU) as a function of HP
compressor rpm (N
2
) and core-inlet temper-
ature (T
2
). The FCU includes a fuel tempera-
ture compensating system to maintain the
required variable-geometry accuracy through-
out the normal fuel temperature range. The
variable-geometry module in the FCU will di-
rect HP fuel to two variable-geometry actua-
tors to operate the inlet and stator vanes.
A feedback system relays the position of the
vanes to the FCU at all times. When the en-
gine is static and during steady-state operation
at lower power, the inlet guide vanes and the
variable stator vane are at a close position.
T h i s r e s t r i c t s t h e a i r f l ow t o t h e H P c o m -
pressor to an amount that will ensure smooth
and continuous stall-free flow through the
compressor. As compressor rpm increases
with the addition of power, the variable-geo-
metry system moves the inlet guide vanes and
the variable stator vanes to the open position,
allowing unrestricted airflow through the com-
pressor. The response of this system will en-
sure a safe surge margin for the compressor
throughout its operating envelope.
FlightSafety Canada
L t é e
L t d .
CL-600-2B16 PILOT TRAINING MANUAL
CL 601-3A
7-3
FOR TRAINING PURPOSES ONLY
ACCESSORY
GEARBOX
RADIAL
DRIVE
SHAFT
FAN DRIVE
SHAFT
FAN
DRIVE
SHAFT
POWER
TAKEOFF
ASSEMBLY
LOW-PRESSURE
TURBINE SECTION
HIGH-PRESSURE
TURBINE SECTION
COMPRESSOR
SECTION
COMBUSTION
SECTION
FRONT FRAME
FAN SECTION
Figure 7-2. CF34 Engine Modules