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engine conditions. The FADEC controls the operation and performance of the engine through three subsystems: fuel control,
compressor airflow management, and engine starting/ignition control.
COMPONENTS AND OPERATION
FADEC UNIT
Critical functions of the FADEC include:
- Control of engine thrust within the required limits, including control of bleed valves, compressor guide vanes
(CGVs), and nacelle anti-ice bleed flow
- Validates N1, N1 limits, and interstage turbine temperature (ITT)
- Thrust reverser operation
- Overspeed circuits
Each powerplant has its own dual-channel FADEC computer. One FADEC channel operates as the in-control channel and
processes information to provide engine control outputs. The other channel operates in standby. The standby channel processes
all the input information but does not provide control output with one exception. Both the in-control and standby
channels will respond to an engine overspeed by commanding the shutoff valve in the fuel metering unit to close in order
to return the engine to an on-speed condition.
The in-control and standby channels continuously share command and status data through a crosstalk data bus. Should the
designated in control channel become unserviceable, the standby channel assumes the in control role.
During normal operations with two serviceable FADEC channels, FADEC software directs the channels to alternate in-control
and standby roles on each successive engine start.
FADEC malfunctions are presented as either caution or advisory messages. Each message has a different impact on the
dispatch ability of the aircraft.
ELECTRICAL POWER
The PMA ensures FADEC supply when N2 is greater than 45%. For engine starting and whenever N2 is below 45%, the
aircraft electrical system supplies power to the FADEC system.
ENGINE IDLE
When the thrust lever is placed at IDLE, the minimum N2 idle rpm is programmed by the FADEC. Idle rpm is dependent
upon atmospheric information, bleed-air loading and phase of flight.
The FADEC will always program the best idle speed for any phase of flight. When the aircraft transitions from one flight
phase to the next, idle rpm is automatically adjusted. There are three different N2 idle settings: flight idle, reverse idle, and
ground idle.
FLIGHT IDLE
Flight idle refers to the idle setting used when the thrust lever is set to idle while airborne (weight-off-wheels).
POWERPLANT
Volume 2 Flight Crew Operating Manual May 06/2005
18-01-06 CSP 100-6 REV 2
ENGINE CONTROL SYSTEM (Cont)
GROUND IDLE
N2 ground idle is the minimum thrust setting. It is selected when weight is on wheels and the thrust lever is idle. Ground
idle varies with altitude and temperature. Increases in altitude or ambient temperature result in an increase in N2 idle rpm.
Decreases in altitude or ambient temperature result in a decrease in N2 idle rpm.
REVERSE IDLE
When reverse idle is selected, reverse balk is activated by the FADEC. Further movement rearward beyond the REV detent
is restricted until the thrust reverser is fully deployed.
SINGLE ENGINE THRUST MANAGEMENT
The FADEC computers continuously crosstalk to share data on the health of each engine. The FADEC will automatically
activate the APR function on the operating engine, should the other engine fail, as long as the TLA is in the TO detent or
above and the APR has not been disabled by the crew.
The FADEC system monitors N2 rpm of both engines. If the mismatch of N2 speed exceeds 15%, the FADEC automatically
increases the N1 speed of the operable engine.
AUTOMATIC POWER RESERVE
When an engine fails, the automatic power reserve (APR) feature of the FADEC will automatically increase the thrust for
the operating engine to the emergency thrust power setting of APR power.
Automatic Power Reserve is available when APR is armed during takeoff if the thrust levers are in the TO detent or above
and if APR has not been disabled by the crew. On the approach, APR is armed for the go-around when in approach configuration
(either engine is available, flaps greater than 20° , or the landing gear is down).
APR power for both engines can also be selected by advancing both thrust levers to the APR stop. A cyan APR icon appears
to the right of each N1 indicator.
ENGINE CONDITION AND FAULT REPORTING (ECFR)
An engine condition and fault reporting system is installed to provide monitoring of engine health. The system periodically
records engine parameters and allows the crew to request that conditions be recorded at anytime. Use of the system entails
downloading data from the FADEC for review by maintenance personnel. The data may be downloaded at anytime to assist
in diagnosing engine problems which may be encountered. The ECFR is intended for maintenance functions and in-flight
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