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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 ControlSystem)- a digital electronic control system- able to autonomously control theengine- throughout its whole operatingrange- in both normal and fault conditions
WHAT IS FADEC?FADEC: (Full Authority Digital Engine ControlSystem)- has a self-monitoring, self-operating,redundant & fail-safe setup- comprises of a digital computerand the other accessories (that controlall the aspects of aircraft engineperformance)
WHAT IS FADEC?FADEC: (Full Authority Digital Engine Control System)- key system of gas turbine engines- provides optimum engine efficiencyfor a given flight condition- also controls engine starting andrestarting.
WHAT IS FADEC?FADEC: (Full Authority Digital Engine Control System)- lowers the work-load of pilots,- reduces the occurrence of piloterrors,- provides for efficient engineoperation.
WHAT IS FADEC?FADEC: (Full Authority Digital Engine Control System)allows the manufacturer to -program engine limitationsand -receive engine health andmaintenance reports.
WHAT IS FADEC?- no form of manual overrideavailable- places full authority to the controlof operating parameters of the enginein the hands of the computer.- if a total FADEC failure occurs, the engine fails.
WHAT IS FADEC?Note: If the engine is controlleddigitally and electronically but allowsfor manual override, it is consideredsolely an Electronic Engine Control(EEC) or Electronic Control Unit (ECU). An EEC, though a componentof a FADEC, is not by itself FADEC.When standing alone, the EEC makesall of the decisions until the pilotwishes to intervene.
DIGITAL ELECTRONIC CONTROLThe benefits of digital electroniccontrol of mechanical systems areevident in greater precision and anability to measure or predictperformance degradation and incipientfailure.Typical examples of this are digitalimplementations of flight control or fly-by-wire (FBW) and digital enginecontrol, or Full-Authority Digital EngineControl (FADEC).
DIGITAL ELECTRONIC CONTROLIntegrated Flight and PropulsionControl (IFPC) allows closer integrationof the aircraft flight control and enginecontrol systems.Flight control systems are virtually allfly-by-wire (FBW) in the modern fighteraircraft of today; the benefits beingweight reduction and improved handlingcharacteristics.
DESIGN REQUIREMENTS OFMODERN 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 digitalcontrol, -improved reliability andperformance, -weight-reduction and -other improvements in systemintegration and data flow.
A BACKGROUNDER The FADEC systems were first usedin the automotive Industry where it iswell proven. Now-a-days airlines and themilitaries all over the worldincorporate it on turbine poweredaircraft.FADECs are made for piston engineand jet engines both but they differin the way of controlling the engine .
A BACKGROUNDER Advanced, intelligent & robustpropulsion controls are critical forimproving the safety andmaintainability of future propulsionsystems. Propulsion system reliability isconsidered to be critical for aircraftsurvival. Hence, FADEC systems cameinto being.
A BACKGROUNDER FADEC is now common on manyengines. Semiconductor and equipmentcooling technology has advancedso that control units can now bemounted on the engine and stillprovide highly reliable operationfor long periods.
A BACKGROUNDER Developing and implementing modernintelligent engine systems requires theintroduction of numerous sensors,actuators and processors to providethe advanced functionality.
A BACKGROUNDER The application of artificialintelligence and knowledge-based system for bothsoftware and hardwareprovides the foundation forbuilding the intelligentcontrol system of the future.
A BACKGROUNDER With time, control systems becamemore sophisticated with theintroduction of additional enginecondition sensors and multipleservo-loops.
A BACKGROUNDERThe task of handling engines waseased by the introduction ofelectronic control in the form ofmagnetic amplifiers in early civil andmilitary aircraft.
A BACKGROUNDERThe magnetic amplifiers allowedengines to be stabilized at any speedin the throttle range by introducing aservo-loop with engine exhaust gastemperature as a measure of enginespeed and an analogue fuel valve tocontrol fuel flow.
A BACKGROUNDERTransistors, integrated circuits andhigh temperature semi-conductorshave all played a part in the evolutionof control systems from rangetemperature control through to fulldigital engine control systems.
A BACKGROUNDERThis allowed the pilot to accelerateand decelerate the engine while thecontrol system limited fuel flows toprevent over- speeds or excessivetemperatures.
A BACKGROUNDERWith modern FADEC systems there areno mechanical control rods ormechanical reversions, and the pilotcan perform carefree handling of theengine throughout the flight envelope.
A BACKGROUNDEROn modern aircraft the engine issupervised by a computer to allow thepilot to operate at maximumperformance in a combat aircraft or atoptimum fuel economy in a passengercarrying aircraft.
A BACKGROUNDERToday, each FADEC is unique andtherefore is expensive to develop,produce, maintain, and upgrade for itsparticular application.
A BACKGROUNDERIn the future, it is desired to establisha universal or common standard forengine controls and accessories. Thiswill significantly reduce the highdevelopment and support costsacross platforms.
LOCATION OF FADECFADEC is normally located on theengine fan casing. Therefore, FADECcooling is difficult.
LOCATION OF FADECHowever, there are many features ofengine control which are distributedaround the engine – such as reversethrust, presently pneumaticallyactuated – which would need to beactuated by alternative means in amore-electric engine. This leads to thepossibility of using distributed enginecontrol.
ELECTRONIC ASPECTS OF FADECModern ECUs use a microprocessorwhich can process the inputs from theengine sensors in real time. Anelectronic control unit contains thehardware and software (firmware).
ELECTRONIC ASPECTS: FADECThe hardware consists of electroniccomponents on a printed circuit board(PCB), ceramic substrate or a thinlaminate substrate. The maincomponent on this circuit board is amicrocontroller chip (CPU).
ELECTRONIC ASPECTS : FADECThe software is stored in themicrocontroller or other chips on thePCB, typically in EPROMs or flashmemory so the CPU can be re-programmed by uploading updatedcode or replacing chips. This is alsoreferred to as an Electronic EngineManagement System (EMS).
HOW DOES FADEC WORK?FADEC works by receiving multipleinput variables of the current flightcondition including air density, throttlelever position, engine temperatures,engine pressures, and many others.
HOW DOES FADEC WORK?Each FADEC is essentially a centralizedsystem, with a redundant, centralcomputer and centrally located analogsignal interfacing circuitry forinterfacing with sensors and actuatorslocated throughout the propulsionsystem.
HOW DOES FADEC WORK?Engine operating parameters such asfuel flow, stator vane position, bleedvalve position and others arecomputed from this data and appliedas appropriate.
HOW DOES FADEC WORK?For example, to avoid exceeding acertain engine temperature, theFADEC can be programmed toautomatically take the necessarymeasures without pilot intervention.The inputs are received by the EECand analyzed up to 70 times persecond.
HOW DOES FADEC WORK?FADEC computes the appropriate thrustsettings and applies them.During flight, small changes inoperation are constantly being made tomaintain efficiency.Maximum thrust is available foremergency situations if the throttle isadvanced to full, but remember,limitations can’t be exceeded.
HOW DOES FADEC WORK?Another new feature of the FADECsystem is the ability to record the last900 hours of flight.With readings taken every second, thisstored information can be used todiagnose problem areas as well asreview recent flight history.
FADEC : FUNCTIONS AIRFRAME ENGINE CONTROL COMMUNICATION REPORT ACQUIRE ENGINE STATUS SENSOR DATA RECEIVE ENGINE PROCESSPOWER COMMAND FADEC 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 :INFRASTRUCTURECONTROL OPERATIONS IN GAS TURBINE ENGINES
FADEC: INFRASTRUCTURECONTROL 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: INFRASTRUCTURESAMPLE CHAIN OF CONTROL (MECH.) OPERATION GEAR DRIVEN WORKING FLUID ACTUATED MECHANICAL PUMP FROM ASSEMBLY ENGINE / AIRCRAFTELECTRO-HYDRO-MECHNICAL MECHANICAL CONTROL UNIT ACTUATORS SERVO POSITION POSITION POSITION SOLENOIDACTUATING SENSORS VALVES SENSOR-1 SENSOR-2 MOTORS FADEC COMPUTER AIRCRAFT COMPUTER COCKPIT
FADEC : INFRASTRUCTURESAMPLE CHAIN OF CONTROL (ELECT.) OPERATION MECHANICAL ACTUATORSELECTRO-HYDRO-MECHNICAL CONTROL UNIT POSITION POSITION SERVO SENSOR-1 SENSOR-2 POSITION SOLENOIDACTUATING SENSORS VALVES MOTORS FADEC COMPUTER PILOT’s THROTTLE VARIOUS INPUTS IN COCKPIT FROM AIRCRAFT POWER DISPLAY PANEL SUPPLY IN COCKPIT VARIOUS INPUTS FROM / COMMANDS TO ENGINE
FADEC: INFRASTRUCTUREHARDWARE:- 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 : INFRASTRUCTURESOFTWARE:- 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: INFRASTRUCTUREINPUTS: 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: INFRASTRUCTURESIMPLIFIED FADEC ARCHITECHTURE This simplified architecture is typical of many dual-channel FADECs. There are two independent lanes: Lane A and Lane B.
FADEC: INFRASTRUCTURESIMPLIFIED 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: INFRASTRUCTURESIMPLIFIED 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 : INFRASTRUCTUREMARKOV ANALYSIS MODEL •By using this model the effects of interrelated failures can be examined. •The model has a total of 16 states as shown by the number in the bottom right-hand corner of the appropriate box.
FADEC : INFRASTRUCTURE MARKOV ANALYSIS MODEL•Each box relates to the serviceabilitystate of the Lane A Command (Ca) andMonitor (Ma) channels and Lane BCommand (Cb) and Monitor (Mb)channels.
FADEC : INFRASTRUCTURE MARKOV ANALYSIS MODEL•These range from the fully serviceablestate in box 1 through a series of failureconditions to the totally failed state in box16.•Clearly most normal operating conditionsare going to be in the left-hand region ofthe model.
FADEC : INFRASTRUCTURE MARKOV MODEL ANALYSIS CaMa .CbMb 6 Ca Ma.CbMb 2 Ca Ma. Cb Mb 7 CaMa . Cb Mb 12 Ca Ma .CbMb 3 Ca Ma.Cb Mb 8 CaMa .Cb Mb 13CaMa.CbMb 1 CaMa . CbMb 16 CaMa. Cb Mb 4 Ca Ma . Cb Mb 9 Ca Ma. CbMb 14 CaMa.Cb Mb 5 Ca Ma .Cb Mb 10 Ca Ma . CbMb 15 CaMa. CbMb 11 NO FAILURE 1 FAILURE 2 FAILURES 3 FAILURES 4 FAILURES DISPACHABLE CONTROLLABLE ENGINE ENGINE 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:INFRASTRUCTUREAll of these failure states result in anengine which may still be controlled bythe FADEC. However, further failuresbeyond this point may result in anengine which may not be controllableeither because both control channelsare inoperative or because the ‘good’control and monitor lanes are inopposing channels or worse.
FADEC:INFRASTRUCTUREThe model shown above is constructedaccording to the following rules: anengine may be dispatched as a ‘get-you-home’ measure provided that onlyone monitor channel has failed.This means that states 3 and 5 aredispatchable: but not states 2, 4, 6, or11 as subsequent failures could resultin 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
FADEC : SCHEMATIC DIAGRAM LP COMPRESSOR STARTING AIR EGV CONTROL & IGNITION HP COMPRESSOR CONTROL AIR EGV CONTROL POWER MAIN FUEL SUPPLY CONTROL CORE AB FUEL CONTROL EECU FADEC FAN AB FUEL AIRCRAFT CONTROL COMPUTER EXHAUST NOZZLE CONTROL FAN DUCT FLAPS CONTROL PILOT BLEED VALVE IN CONTROL COCKPIT
CENTRALIZED CONTROL ARCHITECTUREEach function resides within the FADECControl unique point-to- Centralized Engine and usespoint analog connections to system effectors. Sensor electronics Sensor_1 Sensor electronics Sensor_2 Communication Sensor Communication electronics Sensor_ j CPU / BUS Memory Actuation Actuator_n electronics Power Actuation Actuator_2 electronics Actuation electronics Actuator_1 FADEC
DISTRIBUTED CONTROL ARCHITECTUREFunctions are distributed outside of the Control Centralized Engine FADEC and communicatevia a common interface standard. Sensor electronics Sensor_1 Sensor electronics Sensor_2 Communication Communication Sensor electronics Sensor_ j CPU / Memory BUS Actuation electronics Actuator_n Actuation Power electronics Actuator_2 Actuation electronics Actuator_1 FADEC
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
FADEC : ADVANTAGES - Minimum Maintenance due to On Board Computer Guided Troubleshooting (Aircraft can return to Flying at the Earliest). - Isochronous Idle speed leads to Smoother Engine Starts.
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
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.)