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18-1
P I LOT T R A I N I N G GU I D E
CHAPTER 18: POWER PLANT Introduction
The Challenger 604 is equipped with two General Electric CF34-3B high-bypass ratio
turbofan engines.
The dual-assembly engine consists of a fan rotor (N1) and a compressor rotor (N2). The
N1 rotor is comprised of a single-stage fan connected through a shaft to a four-stage
low-pressure turbine. The N2 rotor is a 14-stage axial flow compressor connected
through a shaft to a two-stage high-pressure turbine. The accessory gearbox is
mechanically driven by the N2 compressor.
Normal takeoff thrust rating is 8729 pounds per engine. During engine-out operation,
the automatic performance reserve (APR) system increases thrust on the operable
engine to 9220 pounds.
Flat-Rated Thrust
Outside air temperature and pressure altitude are determining factors in achieving
takeoff and APR power. Increases in ambient temperature or pressure altitude
adversely affect the engine’s ability to produce rated thrust. The CF34-3B is flat-rated
to ISA + 15°C at sea level.
POWER PLANT
18-2 For Training Purposes Only
May 03
P I LOT T R A I N I N G GU I D E
Engine Construction
Description
The CF34 power plant has two independently rotating major assemblies. The N1
section consists of a fan rotor that is driven through a shaft by a four-stage lowpressure
turbine. The N2 section is comprised of a 14-stage axial flow compressor, a
combustor, an accessory gearbox and a two-stage high-pressure turbine. The
compressor is driven by the high-pressure turbine.
Flow Distribution
Engine airflow passes through the single-stage fan and is divided into two airflow
paths:
• Bypass Air - Air is accelerated by the single-stage N1 fan only and is ducted
around the engine nacelle. Bypass airflow produces approximately 80% of the
thrust at takeoff. Thrust reversers are used to divert the bypass air forward to assist
in airplane braking on the ground.
• Core Air - Air that is accelerated by the N1 fan enters the N2 core where it is
compressed, mixed with fuel, and ignited. The resulting combustion gases are
exhausted through the high-pressure two-stage N2 turbine, which drives the N2
assembly. The exhaust gases are then discharged through the low-pressure fourstage
N1 turbine to drive the N1 fan. Jet pipe thrust produces approximately 20% of
the takeoff thrust.
Flow Distribution
Figure 18-1
Bypass Air
Core Air
N1
IGN B
IGN A
P604_18_002
N2
POWER PLANT
For Training Purposes Only
May 03
18-3
P I LOT T R A I N I N G GU I D E
Major Power Plant Components
N1 Fan
The N1 fan is a single-stage fan that consists of 28 titanium blades. A Kevlar blanket is
wrapped around the inlet housing to contain damage from a failed fan blade. The N1
fan rpm is displayed on the EICAS primary page.
Variable Geometry (VG) Compressor
The VG system regulates airflow across the compressor by changing the position of
the compressor inlet guide vanes and the first five stages of the stator vanes. Fuel
metered by the Fuel Control Unit (FCU) is used to hydraulically change the vane
angle. The VG system optimizes the airflow’s angle of attack at the compressor blades
and provides compressor stall and surge protection.
Accessory Gearbox
The engine-mounted accessory gearbox is driven by the N2 compressor. The gearbox
drives the:
• engine lubrication pumps
• alternator that powers the N1 Control Amplifier
• engine-driven hydraulic pump (Hydraulic Pump 1A or 2A)
• engine-driven fuel pump
• integral drive AC generator (IDG)
Mounted on the gearbox is the air turbine starter (ATS).
The N2 rpm is displayed on the EICAS primary page.
POWER PLANT
18-4 For Training Purposes Only
May 03
P I LOT T R A I N I N G GU I D E
Engine Fuel System
Description
Fuel is delivered to the fuel injectors at pressures and flow rates required to maintain
the desired engine thrust. The engine fuel system, in addition to providing fuel for
combustion, is used for:
• controlling and actuating the VG compressor linkage
• cooling the engine oil (heat exchange)
• actuating and lubricating servos within the Fuel Control Unit (FCU)
• providing motive flow for the main ejector and scavenge ejector pumps
Combustion fuel can be interrupted by moving the thrust lever to SHUTOFF or by
selecting the engine FIRE PUSH switch/light. The SHUTOFF position shuts off the
fuel at the FCU. The FIRE PUSH switch/light closes the fuel shutoff valve.
Components and Operation
Engine-Driven Fuel Pump
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