FADEC
FADEC
• What is FADEC?
• Digital Electronic Controls
• Design Requirements : Modern Engine
Control System
• Why is FADEC Preferred?
• A Backgrounder
• Location of FADEC
• Electronic Aspects of FADEC
• How does FADEC work?
• FADEC : Functions
• FADEC : Essential Features
• FADEC : Infrastructure (Simplified)
• Schematic Diagram
• Advantages & Limitations
WHAT IS FADEC?
FADEC: (Full Authority Digital Engine Control System)
-
a digital electronic control system
-
able to autonomously control the engine
-
throughout its whole operating range
-
in both normal and fault conditions
WHAT IS FADEC?
FADEC: (Full Authority Digital Engine Control System)
has a self-monitoring,
redundant & fail-safe setup
self-operating,
comprises of a digital computer and the
other accessories (that control all the aspects
of aircraft engine performance)
WHAT IS FADEC?
FADEC: (Full Authority Digital Engine Control System)
-
key system of gas turbine engines
provides optimum engine efficiency for a
given flight condition
also controls
restarting.
engine
starting
and
WHAT IS FADEC?
FADEC: (Full Authority Digital Engine Control System)
-
lowers the work-load of pilots,
-
reduces the occurrence of pilot errors,
-
provides for efficient engine operation.
WHAT IS FADEC?
FADEC: (Full Authority Digital Engine Control System)
allows the manufacturer to
-program engine limitations and
-receive engine health and maintenance
reports.
WHAT IS FADEC?
-
no form of manual override available
-
places full authority to the control of
operating parameters of the engine in
the hands of the computer.
-
if a total FADEC failure occurs, the
engine fails.
WHAT IS FADEC?
Note:
If the engine is controlled digitally
and electronically but allows for manual
override, it is
considered solely an Electronic
Engine Control (EEC) or Electronic Control Unit
(ECU).
An EEC, though a component of a
FADEC,
is not by itself FADEC. When
standing alone, the EEC makes all of the
decisions until the pilot
wishes to intervene.
DIGITAL ELECTRONIC CONTROL
The benefits of digital electronic control of
mechanical systems are evident in greater
precision and an ability to measure or predict
performance degradation and incipient
failure.
Typical examples of this are digital
implementations of flight control or fly-by-wire
(FBW) and digital engine control, or FullAuthority Digital Engine Control (FADEC).
DIGITAL ELECTRONIC CONTROL
Integrated Flight and Propulsion Control (IFPC)
allows closer integration of the aircraft flight
control and engine control systems.
Flight control systems are virtually all fly-bywire (FBW) in the modern fighter aircraft of
today; the benefits being weight reduction and
improved handling characteristics.
DESIGN REQUIREMENTS OF MODERN
ENGINE CONTROL SYSTEM
• Speed / Accuracy / Ease of Control
(Least Aircrew Workloads)
• Wide Operational Range
• Reliability & Operational Safety
• Low Operating & Maintenance Costs
• Should Not Add Weight
• Fuel Efficiency
• Dependable Starts
WHY IS FADEC PREFERRED?
New engines are adopting FADEC for
-the benefits offered by digital control,
-improved reliability and performance,
-weight-reduction and
-other
improvements
integration and data flow.
in
system
A BACKGROUNDER
The FADEC systems were first used in the
automotive Industry where it is well proven.
Now-a-days airlines and the militaries all
over the world incorporate it on turbine
powered aircraft.
FADECs are made for piston engine and jet
engines both but they differ in the way of
controlling the engine .
A BACKGROUNDER
Advanced, intelligent & robust propulsion
controls are critical for improving the safety
and maintainability of future propulsion
systems.
Propulsion system reliability is considered to
be critical for aircraft survival. Hence,
FADEC systems came into being.
A BACKGROUNDER
FADEC is
engines.
now
common
on
many
Semiconductor and equipment cooling
technology has advanced so that control
units can now be mounted on the engine
and still provide highly reliable
operation for long periods.
A BACKGROUNDER
Developing and implementing modern
intelligent engine systems requires the
introduction of numerous sensors, actuators
and processors to provide the advanced
functionality.
A BACKGROUNDER
The
application
of
artificial
intelligence and knowledge-based
system for both software and
hardware provides the foundation
for building the intelligent control
system of the future.
A BACKGROUNDER
With time, control systems became more
sophisticated with the introduction of
additional engine condition sensors and
multiple servo-loops.
A BACKGROUNDER
The task of handling engines was eased by
the introduction of electronic control in the
form of magnetic amplifiers in early civil
and military aircraft.
A BACKGROUNDER
The magnetic amplifiers allowed engines to
be stabilized at any speed in the throttle
range by introducing a servo-loop with
engine exhaust gas temperature as a
measure of engine speed and an analogue
fuel valve to control fuel flow.
A BACKGROUNDER
Transistors, integrated circuits and high
temperature semi-conductors have all
played a part in the evolution of control
systems from range temperature control
through to full digital engine control
systems.
A BACKGROUNDER
This allowed the pilot to accelerate and
decelerate the engine while the control
system limited fuel flows to prevent overspeeds or excessive temperatures.
A BACKGROUNDER
With modern FADEC systems there are no
mechanical control rods or mechanical
reversions, and the pilot can perform
carefree handling of the engine throughout
the flight envelope.
A BACKGROUNDER
On modern aircraft the engine is supervised
by a computer to allow the pilot to operate at
maximum performance in a combat aircraft
or at optimum fuel economy in a passenger
carrying aircraft.
A BACKGROUNDER
Today, each FADEC is unique and therefore
is expensive to develop, produce, maintain,
and upgrade for its particular application.
A BACKGROUNDER
In the future, it is desired to establish a
universal or common standard for engine
controls
and
accessories.
This
will
significantly reduce the high development
and support costs across platforms.
LOCATION OF FADEC
FADEC is normally located on the engine fan
casing. Therefore, FADEC cooling is difficult.
LOCATION OF FADEC
However, there are many features of engine
control which are distributed around the
engine – such as reverse thrust, presently
pneumatically actuated – which would need to
be actuated by alternative means in a moreelectric engine. This leads to the possibility of
using distributed engine control.
ELECTRONIC ASPECTS OF FADEC
Modern ECUs use a microprocessor which can
process the inputs from the engine sensors in
real time. An electronic control unit contains
the hardware and software (firmware).
ELECTRONIC ASPECTS: FADEC
The hardware consists of electronic
components on a printed circuit board
(PCB), ceramic substrate or a thin laminate
substrate. The main component on this
circuit board is a microcontroller chip
(CPU).
ELECTRONIC ASPECTS : FADEC
The software is stored in the microcontroller
or other chips on the PCB, typically in EPROMs
or flash memory so the CPU can be reprogrammed by uploading updated code or
replacing chips. This is also referred to as an
Electronic Engine Management System (EMS).
HOW DOES FADEC WORK?
FADEC works by receiving multiple input
variables of the current flight condition
including air density, throttle lever position,
engine temperatures, engine pressures, and
many others.
HOW DOES FADEC WORK?
Each FADEC is essentially a centralized
system, with a redundant, central computer
and centrally located analog signal interfacing
circuitry for interfacing with sensors and
actuators located throughout the propulsion
system.
HOW DOES FADEC WORK?
Engine operating parameters such as fuel
flow, stator vane position, bleed valve
position and others are computed from this
data and applied as appropriate.
HOW DOES FADEC WORK?
For example, to avoid exceeding a certain
engine temperature, the FADEC can be
programmed to automatically take the
necessary
measures
without
pilot
intervention.
The inputs are received by the EEC and
analyzed up to 70 times per second.
HOW DOES FADEC WORK?
FADEC computes the appropriate
settings and applies them.
thrust
During flight, small changes in operation are
constantly being made to maintain efficiency.
Maximum thrust is available for emergency
situations if the throttle is advanced to full, but
remember, limitations can’t be exceeded.
HOW DOES FADEC WORK?
Another new feature of the FADEC system is
the ability to record the last 900 hours of flight.
With readings taken every second, this stored
information can be used to diagnose problem
areas as well as review recent flight history.
FADEC : FUNCTIONS
AIRFRAME
COMMUNICATION
ENGINE CONTROL
ACQUIRE
SENSOR DATA
REPORT
ENGINE STATUS
RECEIVE ENGINE
POWER COMMAND
FADEC
PROCESS
CONTROL LAWS
COMMAND
ACTUATORS
ENGINE HEALTH
MONITORING
DIAGNOSTIC
PROGNOSTIC
ADAPTIVE
FADEC : ESSENTIAL
FEATURES
-
Control & Monitoring of Engine Operations
-
Dual Channels & Redundancy
-
Engine Life Monitoring
-
Record of Engine Performance Parameters
-
Automated Troubleshooting
-
Memory Read or Recall of Engine Data
-
Control of Common Engine Problems
-
Display of Warnings
-
Adaptation
-
Isochronous Idle Speed
FADEC :INFRASTRUCTURE
CONTROL OPERATIONS IN GAS TURBINE ENGINES
FADEC: INFRASTRUCTURE
CONTROL OPERATIONS IN GAS TURBINE ENGINES
- Air Control (Compressor Entry)
- Fuel Control (Main / AB / Starting System)
- Starting & Ignition Control
- Lubrication Control
- Surge Control (Through Bleed Valve)
- Thrust Control (Through Exhaust Nozzle)
- Vibration Control (Through Air / Fuel Control)
FADEC: INFRASTRUCTURE
SAMPLE CHAIN OF CONTROL (MECH.) OPERATION
GEAR DRIVEN
MECHANICAL PUMP
WORKING FLUID
FROM
ENGINE / AIRCRAFT
ACTUATED
ASSEMBLY
ELECTRO-HYDRO-MECHNICAL
CONTROL UNIT
SERVO
ACTUATING
MOTORS
POSITION
SENSORS
MECHANICAL
ACTUATORS
POSITION POSITION
SENSOR-1 SENSOR-2
SOLENOID
VALVES
FADEC COMPUTER
AIRCRAFT COMPUTER
COCKPIT
FADEC : INFRASTRUCTURE
SAMPLE CHAIN OF CONTROL (ELECT.) OPERATION
MECHANICAL
ACTUATORS
ELECTRO-HYDRO-MECHNICAL
CONTROL UNIT
POSITION POSITION
SENSOR-1 SENSOR-2
SERVO
POSITION SOLENOID
ACTUATING
SENSORS
VALVES
MOTORS
FADEC
COMPUTER
VARIOUS INPUTS
FROM AIRCRAFT
PILOT’s THROTTLE
IN COCKPIT
POWER
SUPPLY
VARIOUS INPUTS FROM /
COMMANDS TO ENGINE
DISPLAY PANEL
IN COCKPIT
FADEC: INFRASTRUCTURE
HARDWARE:
- Dual Power Supply
-
FADEC Computer (With Logic Circuit PCBs & Programmed /
Programmable Memory)
A Set of Servo Actuating Motors / Solenoid Valves / Position
Sensors (for every System Control Unit)
Dual Position Sensors for Actuators (of every System)
A Set of Electrical Harnesses (for every System)
Display Panel with Indicators / Warning Lights (in Cockpit)
Multiple Engine RPM, Pressure Sensors & Thermocouples
Pilot’s Throttle
FADEC : INFRASTRUCTURE
SOFTWARE:
- EPR Schedules (For Thrust, over Entire Range of
Engine Operation Without FADEC Computer Failure)
- N Schedules (For Thrust as per Pilot’s Throttle,
Engine Operation in case of Limited FADEC Computer
Functionality)
Note: In case of certain degree of FADEC failure,
there is an automatic mode switch-over from EPR to
N rating. However, if the failure disappears, the
pilot can reset the mode to switch-back to EPR
mode.
FADEC: INFRASTRUCTURE
INPUTS:
From Aircraft.
-
Ambient Temperature
Altitude
Mach Number
Angle of Attack
Impact Pressure
Landing Gear Position
Missile / Rocket Firing Signals etc.
FADEC: INFRASTRUCTURE
INPUTS:
From Engine.
-
Throttle Lever Position
RPM
Turbine Outlet / Exhaust Gas Temperature
Exhaust Nozzle Area
Fan Duct Flaps Position
Bearing Temperatures
Engine Vibration
Engine Pressures
FADEC: INFRASTRUCTURE
SIMPLIFIED FADEC ARCHITECTURE
FADEC LANE-A
FADEC
LANE-A
CONTROL
ENGINE
THRUST
DEMAND
FADEC LANE-B
FADEC
LANE-B
CONTROL
FADEC
LANE-A
MONITOR
FADEC
LANE-B
MONITOR
ENGINE
FUEL
DEMAND
FADEC: INFRASTRUCTURE
SIMPLIFIED FADEC ARCHITECHTURE
This simplified architecture is typical of
many dual-channel FADECs.
There are two independent lanes: Lane A
and Lane B.
FADEC: INFRASTRUCTURE
SIMPLIFIED FADEC ARCHITECHTURE
Each lane comprises a Command and
Monitor portion, which are interconnected
for cross monitoring purposes, and
undertakes the task of metering the fuel
flow to the engine in accordance with the
necessary control laws to satisfy the flight
crew thrust command.
FADEC: INFRASTRUCTURE
SIMPLIFIED FADEC ARCHITECHTURE
The analysis required to decide upon the
impact of certain failures in conjunction
with others, requires a Markov model in
order to be able to understand the
dependencies.
FADEC : INFRASTRUCTURE
MARKOV ANALYSIS MODEL
•By using this model the effects
interrelated failures can be examined.
of
•The model has a total of 16 states as
shown by the number in the bottom righthand corner of the appropriate box.
FADEC : INFRASTRUCTURE
MARKOV ANALYSIS MODEL
•Each box relates to the serviceability state of
the Lane A Command (Ca) and Monitor (Ma)
channels and Lane B Command (Cb) and
Monitor (Mb) channels.
FADEC : INFRASTRUCTURE
MARKOV ANALYSIS MODEL
•These range from the fully serviceable state in
box 1 through a series of failure conditions to the
totally failed state in box 16.
•Clearly most normal operating conditions are
going to be in the left-hand region of the model.
FADEC : INFRASTRUCTURE
MARKOV MODEL ANALYSIS
CaMa.CbMb 6
CaMa.CbMb 2
CaMa.CbMb 7
CaMa.CbMb 12
CaMa.CbMb 3
CaMa.CbMb 8
CaMa.CbMb 13
CaMa.CbMb 1
CaMa.CbMb 16
CaMa.CbMb 4
CaMa.CbMb 9
CaMa.CbMb 14
CaMa.CbMb 5
CaMa.CbMb 10
CaMa.CbMb 15
CaMa.CbMb 11
NO FAILURE
4 FAILURES
1 FAILURE
DISPACHABLE
ENGINE
2 FAILURES
CONTROLLABLE
ENGINE
3 FAILURES
ENGINE
SHUT-DOWN
FADEC: INFRASTRUCTURE
Concentrating on the left-hand side of the model it
can be seen that the fully serviceable state in box 1
can migrate to any one of six states:
– Failure of Command channel A results in state 2
being reached.
– Failure of Monitor channel A results in state 3
being reached.
– Failure of Command channel B results in state 4
being reached.
– Failure of Monitor channel B results in state 5
being reached.
– Failure of the cross-monitor between Command A
and Monitor A results in both being lost
simultaneously and reaching state 6.
– Failure of the cross-monitor between Command B
and Monitor B results in both being lost
simultaneously and reaching state 11.
FADEC: INFRASTRUCTURE
All of these failure states result in an engine
which may still be controlled by the FADEC.
However, further failures beyond this point may
result in an engine which may not be
controllable either because both control
channels are inoperative or because the ‘good’
control and monitor lanes are in opposing
channels or worse.
FADEC: INFRASTRUCTURE
The model shown above is constructed
according to the following rules: an engine
may be dispatched as a ‘get-you-home’
measure provided that only one monitor
channel has failed.
This means that states 3 and 5 are
dispatchable: but not states 2, 4, 6, or 11 as
subsequent failures could result in engine
shut-down.
FADEC: ESSENTIAL FEATURES
MILITARY / TRANSPORT AIRCRAFT
- Compressor Entry Guide Vanes Control
(For LP Compressor & HP Compressor)
- Main Fuel Control
- AB Fuel Control (For Core & Fan AB)
- Starting Fuel Control & Ignition Control
- Bleed Valve Control & Fan Duct Flaps
Control
- Exhaust Nozzle Control
- Lubrication Control & Vibration Control
FADEC : SCHEMATIC DIAGRAM
LP COMPRESSOR
AIR EGV CONTROL
STARTING
&
IGNITION
CONTROL
HP COMPRESSOR
AIR EGV CONTROL
POWER
SUPPLY
AIRCRAFT
COMPUTER
MAIN FUEL
CONTROL
FADEC
EECU
CORE AB FUEL
CONTROL
FAN AB FUEL
CONTROL
EXHAUST NOZZLE
CONTROL
FAN DUCT FLAPS
CONTROL
PILOT
IN
COCKPIT
BLEED VALVE
CONTROL
CENTRALIZED CONTROL ARCHITECTURE
Engine
Control
Each function residesCentralized
within the FADEC
and uses
unique point-to-point analog
connections to system effectors.
Sensor
electronics
Sensor
electronics
Sensor_1
Sensor_2
Communication
Sensor
electronics
CPU /
Memory
Power
FADEC
Sensor_ j
BUS
Communication
Actuation
electronics
Actuator_n
Actuation
electronics
Actuation
electronics
Actuator_2
Actuator_1
DISTRIBUTED CONTROL ARCHITECTURE
Functions are distributed
outside of the
FADECControl
and communicate via a
Centralized
Engine
common interface standard.
Communication
CPU /
Memory
Power
FADEC
BUS
Communication
Sensor
electronics
Sensor_1
Sensor
electronics
Sensor_2
Sensor
electronics
Sensor_ j
Actuation
electronics
Actuator_n
Actuation
electronics
Actuator_2
Actuation
electronics
Actuator_1
FADEC : ADVANTAGES
- Reduced Aircrew Workload.
- Improved Fuel Efficiency up to 15%
(Due to faster, Accurate Engine
Control no trimming is required).
- Reduced Aircraft Weight and Engine
Size (Due to Absence of Heavy
Mechanical
Assemblies,
No
Scattering of Pipelines & Electrical
Wirings).
- Enhanced Engine Life (Due to Engine
Operation in Safer / Mean Range).
- Improved
Reliability
(Due
to
Redundancy and Dual Channel).
FADEC : ADVANTAGES
- Minimum Maintenance due to On Board
Computer
Guided
Troubleshooting
(Aircraft can return to Flying at the
Earliest).
- Isochronous Idle speed
Smoother Engine Starts.
leads
to
FADEC : ADVANTAGES
- Maximum Performance in a combat
aircraft or at Optimum Fuel Economy
in a Transport Aircraft are possible
after
necessary
Adaptation
/
Programming of FADEC Computer.
- Auto-testing removes the need for
test-running the engine after minor
maintenance work ( Resulting in
annual savings of millions of gallon of
fuel for the fleet.
FADEC : LIMITATIONS
- Pilot can not override the FADEC
Control.
- In the event of complete FADEC
Failure, pilot left with no other option
than having to fly with least
performance, just sufficient to land
safely. (This limitation has been
removed in modern transport aircraft
by having two FADEC Computers.)
FADEC: ANY QUESTION
?