Full-Authority-Digital-Engine-Control-FADEC-System.pdf

TRIBHUWAN UNIVERSITYINSTITUTE OF ENGINEERING

PULCHOWK CAMPUS

A REPORT ONFADEC

A PROPITIOUS INVENTION,ITS

OPERATION AND FUTURE ADVANCEMENT

Submitted to:Sudip Bhattarai

Submitted by:ANMESH GAIRE (067/BME/604)PUSKAR KHANAL (067/BME/628)SAMIKARAN BHATTARAI (067/BME/636)SAWAN ADHIKHARI (067/BME/640)

12th August, 2014

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Abstract

FADEC, an acronym for Full Authority Digital Engine Control, has been statedas close to perfection technology that one will ever find. This paper presents theadvantages, operation and possible improvements of FADEC system. The FADECsystem primarily does three functions: Engine control, safety and diagnostics andData logging. It eliminates the need for the use of magnetos, carburetor heat, mix-ture controls and engine priming. Preinstalled single throttle lever in FADEC re-duces the tiresome task for the pilots to monitor and control the air fuel mixture.By doing so, they increase the efficiency of the engine by 15%. Basic componentsused in FADEC are: Two Electronic Control Units (ECUs), Central Air digitalComputer (CADC), Health Status Annunciator (HSA) and FADEC sensor sets.Sensor sets detects the temperature, pressure, throttle position. The information iscarried to CADC. CADC converts the analogue data to digital and send them toECUs. ECU the brain of FADEC analyzes the data and guides actuators to oper-ate accordingly. All the action carried out by FADEC will be displayed to pilotsthrough HSA. Undoubtedly, FADEC has been a boon to aviation but they too arenot free from voids. Despite coming up with better solutions at times, pilots can-not override the decisions of FADEC. Likewise, use of centralized operation hasreduced the life of FADEC. Advancement in these parameters would transformFADEC from a close to perfection to a perfect technology.

Contents

1 INTRODUCTION 21.1 DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 ADVANTAGES . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 COMPONENTS AND OPERATION OF FADEC 52.1 COMPONENTS . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2 OPERATION OF FADEC . . . . . . . . . . . . . . . . . . . . . 62.3 USE OF SENSOR IN FADEC . . . . . . . . . . . . . . . . . . . 8

3 USE OF FADEC IN MODERN AIRCRAFT 12

4 FUTURE ADVANCEMENT 14

5 SUMMARY 15

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Chapter 1

INTRODUCTION

1.1 DEFINITION

FADEC, doesnt just live up to all the advanced billing, it leaps over it.

-Ben Smith-

Pilots have long sought automatic assistance for the engine management system.Well, the solution has arrived in the appearance of FADEC. Full Authority DigitalEngine Control (FADEC) is merely a system with digital computer, sensors andactuators that control an aircrafts engine and propeller. The major functions ofFADEC include monitoring and controlling the fuel and ignition portions of theengine. First used in turbine-powered aircraft, this cutting edge technology hasquickly found its way in piston powered aircraft. The FADEC system primarilydoes three functions: Engine control, safety and diagnostics and Data logging.Likewise, its ability in controlling the fuel pump and adjusting the amount of fuelinjection during the combustion process assist it in maintaining high efficiency.

Figure 1.1: Different types of FADEC produced by SAGEM

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1.2 HISTORY

The FADEC system is the result of an aggressive program of Aerosance ( a TCMcompany) to certify such systems in aircrafts. If rumors are to be believed, theFADEC system was reverse engineered from similar system in General MotorsCadillac Northstar V-8. The then recently introduced Cadillac Northstar V-8 useda computer to control the mixture and spark advance system for each cylinder. Al-though the system was developed by Aerosance in the late 1990s, the system tooklong to be introduced to piston powered aircrafts. By July of 2007, there were onlytwo aircrafts in the United States that had factory installed FADEC systems: TheThielert powered Diamond DA42 and the Teledyne Continental Motors poweredLiberty XL-2, the liberty XL-2 being the first one to be certified for use of FADECin 2005. Due to high costs and equally high maintenance charges, these systemsposed to be quite expensive. The FAA regulations also hindered its way to pistonpowered aircrafts. The FADEC to be installed in aircrafts must pass high levels oflightening, vibration and EMI testing which surpasses the automobile standards.FADEC systems are currently in operation in many aircrafts which includes mil-itary aircraft F-18E/F and Euro fighter and the commercial aircrafts Airbus 320,321 and Boeing 777.

1.3 ADVANTAGES

During the starting of the aircraft, FADEC adjusts the fuel to air mixture and posi-tions the throttle based on the relative environmental parameters. Likewise, duringflight condition, FADEC constantly monitors the engine and adjusts the fuel flow.Moreover, FADEC systems eliminate the need for the use of magnetos, carbure-tor heat, mixture controls and engine priming. Preinstalled single throttle lever inFADEC reduces the tiresome task for the pilots to monitor and control the air fuelmixture. The pilot just needs to position the throttle lever to a desired output suchas start, idle; cruise power or maximum power, and the FADEC system adjust theengine automatically for the desired output. As the work is done automaticallyair-fuel mixture is leaned in each cylinder which maximizes performance and effi-ciency in all conditions.The other advantages of FADEC have been described below:

1. Limiting the disadvantages of carburetorA very important advantage of fuel injection is that it eliminates the risk ofcarburetor icing. Carburetor ice occurs due to the effect of fuel vaporizationand the decrease in air pressure in the venture meter, which causes a sharptemperature drop in the carburetor. If water vapor in the air condenses when

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the carburetor temperature is at or below freezing, ice may form on inter-nal surfaces of the carburetor, including the throttle valve. The reduced airpressure, as well as the vaporization of fuel, contributes to the temperaturedecrease in the carburetor. This restricts the flow of the fuel/air mixture andreduces power. If enough ice builds up, the engine will suddenly stop withlittle or no warning. Carburetor ice is most likely to occur when temper-atures are below 20C (70F) and the relative humidity is above 80 percent.However, due to the sudden cooling that takes place in the carburetor, icingcan occur even with temperatures as high as 38C (100F) and humidity as lowas 50 percent. This temperature drop can be as much as 20C (70F0).The ECU has a complete 3D map programmed into it so it can decide on howlong each injector needs to be open to get the right amount of fuel through inall different circumstances. Looking at RPM and throttle position the ECUcalculates the amount of air going into the engine and sets the injector tim-ing accordingly. FADEC unit will even fine tune the fuel flow to compensatefor changes in barometric pressure as well as inlet air temperature in theinlet collector. The higher the aircraft goes, the more the barometric pres-sure drops so less fuel will need to be injected. When the inlet air changes(not only differences in hot or cold days, but also as the aircraft climbs) theamount of fuel will be adapted.

2. Single lever controlFADEC reduces a pilots engine management tasks to simply selecting thedesired power setting through a single control. Pilots can now forget aboutmanaging the engine and focus on flying. The recreational pilot doesnt re-ally want all the hassle, but just wants to enjoy flying. With just the throttleto adjust, there is certainly less risk for the pilot (and certainly less experi-enced ones) to forget something (for example applying carburetor heat) ordo something wrong such as flooding the carburetor on start-up or leaning ittoo much and possibly damaging the engine.With single lever control and FADEC taking care of all of the engine man-agement tasks, the risk of pilot error is much reduced. As human error is stilllarge factor in many accidents we believe the FADEC controlled engine willincrease safety in general in any powered aircraft.

3. Extra featuresAnother safety feature is that it controls the electric fuel pump. If the en-gine stops, it will shut-off the fuel pump automatically. If the fuel wouldnot be shut-off immediately, fuel leaks and continuing fuel circulation underpressure could cause fire and the hazard of explosion.

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Chapter 2

COMPONENTS ANDOPERATION OF FADEC

2.1 COMPONENTS

Main components used in FADEC system are listed below:

Two Electronic Control Units (ECUs) Central Air digital Computer(CADC) Health Status Annunciator (HSA) FADEC sensor sets

ECUs are the brain of the engine control system. They perform the most importanttask of receiving the output from sensors, analyzing it and taking the immediaterequired action. ECU is divided into an upper and lower portion. Lower portioncontains the Electronic Circuit Board that processes all data whereas; upper portioncontains the ignition coils for the spark plugs. Lower portion of each ECU containstwo microprocessors. One microprocessor is assigned for one cylinder. Let us say,cylinder 1 and 2 are operated by ECU no.1 and cylinder 3 and 4 are operated byECU no.2. If any problem is encountered with ECU no.1, cylinder no. 1 and 2will be operated by ECU no. 2. This is the backup plan which has been mentionedearlier.The CADC (Central Air Digital Computer) consists of a analogue to digital con-verter, several quartz pressure sensors, and the microprocessor. Inputs to the systemincludes the primary flight controls, a number of switches, static and dynamic airpressure (for calculating stall points and aircraft speed) and a temperature gauge.

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The output controls the primary flight controls, wing sweep and the flaps.FADEC sensor set are used to detect speed, cylinder head temperature, exhaustgas temperature, manifold air pressure, manifold air temperature, fuel pressureand throttle position. Health Status Annunciator(HSA) consists of five lights onpanel and WOT .HSA provides information regarding the status of the FADECsystem. Whenever, any problem is encountered, following warnings might pop upin FADEC windows:

FADEC WARN: Engine Failure may be imminent, more than one cylinderis affected, land ASAP

FADEC CAUTION: 99.9% of installed components are working. No promptaction is required.

PPWR FAIL: Primary Battery is not being charged, will be accompaniedby EBAT FAIL, you will start draining both batteries and have at least 60minutes to land. Your secondary battery will only power FADEC, AI, andTurn Coordinator

EBAT FAIL: Backup Battery not being charged, everything can run fromPrimary Power Source/Battery.

FUEL PUMP: illuminates when Fuel Boost Pump Mode Switch is in ON orOFF. If this light is illuminated it means that you are manually controlling thefuel pump or that the fuel pressure is out of the 20-40 psi range. Illuminatesfor electric driven fuel pump as well as engine driven pump.

WOT: It is situated below HSA panel. Illuminates when Throttle PositionSwitch (TPS) is contacted (full throttle), signal sent to ECU that max poweris required which causes FADEC to set fuel to air ratio for Best Power.

2.2 OPERATION OF FADEC

As the name suggests these sensors are employed to detect speed, temperature,pressure, throttle position and they are equipped at particular functional positions.The output from the sensors is flown to Central Air Data computer (CADC) andthen to Electronic Control Units (ECUs) for data processing and analysis.Each ECUs has two Central Air Data computer (CADC) inputs. All the sensorsmentioned above flow their outputs to CADC before they are sent to ECUs. Thereis cross link between each ECUs and CADC which helps in normal operation

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during failure of one CADC inputs. Generally, CADC receives inputs from fivesources:

1. Static pressure sensor

2. Dynamic pressure sensor

3. Analog pilot information

4. Temperature probe and

5. Digital switch pilot input

Figure 2.1 cross link between ECUs and CADCs

Failure of one CADC inputs does not have any effect but when both CADC inputsfail to operate, FADEC operates in alternative way. That is, FADEC takes the lat-est input sensed by CADC to calculate thrust. Now, FADEC utilizes an internal,fixed routine to determine thrust level for the selected throttle position. However,internal routine may cause the trust to increase but it will never cause the thrustto decrease. After the detection of information, ECUs direct actuator to performaccordingly.The FADEC system continuously monitors fuel and ignition conditions. The ECUunits receive information from sensors via the Low Voltage Harness which inter-faces with the MPC units via 50-pin connectors. The status of the FADEC systemis conveyed to the pilot by the HSA. Discrete lamps in the HSA will illuminateupon detection of system faults and during some normal control actions.Sensor input to each control channel includes engine speed, crank position, fuelpressure, intake manifold air pressure, intake manifold air temperature and WideOpen Throttle (WOT) position. In addition, each control channel also receives

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exclusive signals for measuring its cylinders head temperature and exhaust gastemperature.The ECU units use the signals from sensors to determine the required fuel mix-ture and ignition timing for its cylinders next combustion event. The required fuelquantity is injected into each cylinder intake port at the appropriate time, with re-spect to crank position, by a solenoid style fuel injector. The injectors control coilis driven directly by the associated control channel.FADEC systems are either powered by the aircrafts main electrical engine or froma separate generator connected to the engine. However, a backup source of 12 or24 voltages is available for both the cases because failure of FADEC system couldresult in complete loss of engine thrust. To eliminate the loss of thrust, two separateand identical digital channels are installed which are capable of providing thrust toall engines. Two channels are housed in one assemble but are physically separated.FADEC comes with an impressive improvement to the electrical system. In theevent of an alternator failure, the automatic bus tie will connect the buses together.This event requires no input from the pilot and the alternator which still remainsonline supporting night time operations.

2.3 USE OF SENSOR IN FADEC

Sensor is a device that is designed to transform acoustic, biological, chemical, elec-trical, magnetic, mechanical, optical, radiation or thermal stimuli into an electricalsignal for the purpose of transmitting information. Sensors and sensing techniquesare needed to be integrated into the FADEC. This requires the addition of signalconditioners and software addition to the control algorithms. Signal conditioningof the signal may involve amplification, filtering, and may contain some. All thesensors need to be interfaced with the hardware through analog signal multiplexerand analog-to-digital converters.

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Figure 2.2: Different Sensors and their location

FADEC systems employ three types of sensors:

Control sensor Feedback sensor and Diagnostic sensorsControl sensors are critical to maintaining stable engine operation including

temperatures, pressures, and speed measurement. Feedback sensors are primar-ily position sensors for measurement and control of actuator position. Diagnosticsensors may include all control sensor types and additionally, vibration, strain, In-frared, and gas measurement.Control loops are required to maintain safe and stable engine operation. Eachsensor is routed to a central Controller (FADEC). Todays manufacturer employsdedicated wiring for each measurement and actuation location. Figure 2.3 showstypical sensors suits used in a typical turbine engine control.

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Figure2.3: Block Diagram for components and data flow in FADEC

At present, all the FADEC systems are installed in centralized way. All the infor-mation is carried only after being passed from it.

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Figure 2.4 : Centralized FADEC system[http://www.decwg.org/pages/current.html]

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Chapter 3

USE OF FADEC IN MODERNAIRCRAFT

Alike every electronic goods, FADEC are improved and optimized periodically.FADEC are classified into different generations according to their latest version.Three generations of FADECs for powerful civilian aircraft engines have been de-veloped one after another.

Table 3: Use of FADEC in different Aircrafts

Capable of controlling single or dual channel turboprops, turbo shafts, turbo-jets and turbofans, FADECs control the various actuators in real time by continu-ously processing and analyzing data collected by multiple sensors (oil, kerosene,engine, ignition, alternator, etc.). Equipped with a comprehensive set of built-intests, FADECs are designed to resist severe environments (electromagnetic inter-ferences, lightning, contaminations, vibrations, high temperatures, etc.) and offerlower costs of ownership. Featured in several programs such as CFM56, CF6,GE90, GEnx, TP400, GP7200 and SaM146 engines, Developed and built along-side BAe Systems within the framework of the FADEC International joint venture,FADEC 3s processing power is 10 times higher than its predecessors for the same

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overall size. Its highly embedded electronic architecture features several new func-tions such as maintenance and diagnostic functions, in particular. Among its mul-tiple tasks, FADEC 3 controls engine thrust, interfaces with the thrust reverser andensures electronic engine protection in case of over speed, etc. FADEC 3 equipsthe GE90-115B, the Boeing 777 Extended Range most powerful aircraft engine inthe world.

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Chapter 4

FUTURE ADVANCEMENT

FADEC has been a boon to Aircraft. It has reduced concentration of pilots andincreased efficiency by 15%. However, we can expect further advancement formthe device in the future.FADEC are programmed by the manufacturer and the installed program varies fordifferent engines. As it operates within the given code, pilot cannot override itsdecision, despite coming up with better solutions at times.Most importantly, the current centralized FADEC system must be replaced withdistributed FADEC system. Distributed system will increase the life cycles ofFADEC and would provide greater flexibility. NASA has been carrying out thisresearch. The success in the research will certainly revolutionize FADEC.

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Chapter 5

SUMMARY

It has been quite clearly stated that FADEC has made aircraft performance farbetter. They have been able to eliminate the need for magnetos, carburetor heat,mixture controls and engine priming as well. Due to presence of automatic sensingand optimum fuel supply, the system also proves to be advantageous in increasingfuel efficiency and overall performance of the engine. Moreover the best part ofusing FADEC is that the engine starts with a push of a button. The pilot gains moretime and concentration since he is relieved from several responsibilities like lean-ing or enriching the fuel mixture. Thus he can focus on keeping above blue-line,stowing the gear and flying the airplane even in critical conditions like engine out.Still the system is not void of disadvantages. During critical conditions the sys-tem does not provide with manual override. Therefore the pilot has nothing to dothan pray that the system performs reliably and according to he wishes. Although,research is being carried out, no solution has been obtained for centralized sys-tem. Despite these limitations, FADEC has been proved as a boon for Aircraftindustries.

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Bibliography

[1] Khan A. MD. (et al.) 2013. Experimental study of FADEC systemon Lycoming engine. International Journal of Modern engineeringResearch

[2] Smith D. 2007. FADEC: Aviation maintenance

[3] FADEC Powerpoint presentation. Liberty XL2

[4] Menne C. 2007. FADEC is here, Malibu Mirage

[5] Airplane and systems description. Liberty Aerospace

[6] Engine control units.Available at: http://www.sagem.com/spip.php?rubrique16

[7] Cenntrally controlled FADEC.Available at: http://www.decwg.org/pages/current.html

[8] FADEC.Available at: http://en.wikipedia.org/wiki/FADEC

[9] CADC.Available at: http://en.wikipedia.org/wiki/CADC

[10] Behhahahi.R.A 2006. Need for Robust sensors for inherently failsafe gas turbine engine controls, monitors and prognostics. Air forceresearch laboratory.

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