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

TRIBHUWAN UNIVERSITY INSTITUTE OF ENGINEERING PULCHOWK CAMPUS

A REPORT ON FADEC A PROPITIOUS INVENTION, ITS OPERATION AND FUTURE ADVANCEMENT

Submitted to: Sudip Bhattarai Submitted by: ANMESH GAIRE PUSKAR KHANAL SAMIKARAN BHATTARAI SAWAN ADHIKHARI

(067/BME/604) (067/BME/628) (067/BME/636) (067/BME/640)

12th August, 2014 1

Abstract FADEC, an acronym for Full Authority Digital Engine Control, has been stated as close to perfection technology that one will ever find. This paper presents the advantages, operation and possible improvements of FADEC system. The FADEC system primarily does three functions: Engine control, safety and diagnostics and Data logging. It eliminates the need for the use of magnetos, carburetor heat, mixture controls and engine priming. Preinstalled single throttle lever in FADEC reduces 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 components used in FADEC are: Two Electronic Control Units (ECUs), Central Air digital Computer (CADC), Health Status Annunciator (HSA) and FADEC sensor sets. Sensor sets detects the temperature, pressure, throttle position. The information is carried to CADC. CADC converts the analogue data to digital and send them to ECUs. ECU the brain of FADEC analyzes the data and guides actuators to operate accordingly. All the action carried out by FADEC will be displayed to pilots through HSA. Undoubtedly, FADEC has been a boon to aviation but they too are not free from voids. Despite coming up with better solutions at times, pilots cannot override the decisions of FADEC. Likewise, use of centralized operation has reduced the life of FADEC. Advancement in these parameters would transform FADEC from a close to perfection to a perfect technology.

Contents 1

INTRODUCTION 1.1 DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 ADVANTAGES . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 2 3 3

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COMPONENTS AND OPERATION OF FADEC 2.1 COMPONENTS . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 OPERATION OF FADEC . . . . . . . . . . . . . . . . . . . . . 2.3 USE OF SENSOR IN FADEC . . . . . . . . . . . . . . . . . . .

5 5 6 8

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USE OF FADEC IN MODERN AIRCRAFT

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4

FUTURE ADVANCEMENT

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5

SUMMARY

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

Figure 1.1: Different types of FADEC produced by SAGEM 2

1.2

HISTORY

The FADEC system is the result of an aggressive program of Aerosance ( a TCM company) to certify such systems in aircrafts. If rumors are to be believed, the FADEC system was reverse engineered from similar system in General Motors Cadillac Northstar V-8. The then recently introduced Cadillac Northstar V-8 used a computer to control the mixture and spark advance system for each cylinder. Although the system was developed by Aerosance in the late 1990s, the system took long to be introduced to piston powered aircrafts. By July of 2007, there were only two aircrafts in the United States that had factory installed FADEC systems: The Thielert powered Diamond DA42 and the Teledyne Continental Motors powered Liberty XL-2, the liberty XL-2 being the first one to be certified for use of FADEC in 2005. Due to high costs and equally high maintenance charges, these systems posed to be quite expensive. The FAA regulations also hindered its way to piston powered aircrafts. The FADEC to be installed in aircrafts must pass high levels of lightening, vibration and EMI testing which surpasses the automobile standards. FADEC systems are currently in operation in many aircrafts which includes military 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 positions the throttle based on the relative environmental parameters. Likewise, during flight condition, FADEC constantly monitors the engine and adjusts the fuel flow. Moreover, FADEC systems eliminate the need for the use of magnetos, carburetor heat, mixture controls and engine priming. Preinstalled single throttle lever in FADEC reduces the tiresome task for the pilots to monitor and control the air fuel mixture. The pilot just needs to position the throttle lever to a desired output such as start, idle; cruise power or maximum power, and the FADEC system adjust the engine automatically for the desired output. As the work is done automatically air-fuel mixture is leaned in each cylinder which maximizes performance and efficiency in all conditions. The other advantages of FADEC have been described below: 1. Limiting the disadvantages of carburetor A very important advantage of fuel injection is that it eliminates the risk of carburetor icing. Carburetor ice occurs due to the effect of fuel vaporization and the decrease in air pressure in the venture meter, which causes a sharp temperature drop in the carburetor. If water vapor in the air condenses when 3

the carburetor temperature is at or below freezing, ice may form on internal surfaces of the carburetor, including the throttle valve. The reduced air pressure, as well as the vaporization of fuel, contributes to the temperature decrease in the carburetor. This restricts the flow of the fuel/air mixture and reduces power. If enough ice builds up, the engine will suddenly stop with little or no warning. Carburetor ice is most likely to occur when temperatures are below 20C (70F) and the relative humidity is above 80 percent. However, due to the sudden cooling that takes place in the carburetor, icing can occur even with temperatures as high as 38C (100F) and humidity as low as 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 how long each injector needs to be open to get the right amount of fuel through in all different circumstances. Looking at RPM and throttle position the ECU calculates the amount of air going into the engine and sets the injector timing accordingly. FADEC unit will even fine tune the fuel flow to compensate for changes in barometric pressure as well as inlet air temperature in the inlet collector. The higher the aircraft goes, the more the barometric pressure 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) the amount of fuel will be adapted. 2. Single lever control FADEC reduces a pilot’s engine management tasks to simply selecting the desired power setting through a single control. Pilots can now forget about managing the engine and focus on flying. The recreational pilot doesn’t really want all the hassle, but just wants to enjoy flying. With just the throttle to adjust, there is certainly less risk for the pilot (and certainly less experienced ones) to forget something (for example applying carburetor heat) or do something wrong such as flooding the carburetor on start-up or leaning it too much and possibly damaging the engine. With single lever control and FADEC taking care of all of the engine management tasks, the risk of pilot error is much reduced. As human error is still large factor in many accidents we believe the FADEC controlled engine will increase safety in general in any powered aircraft. 3. Extra features Another safety feature is that it controls the electric fuel pump. If the engine stops, it will shut-off the fuel pump automatically. If the fuel would not be shut-off immediately, fuel leaks and continuing fuel circulation under pressure could cause fire and the hazard of explosion.

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Chapter 2

COMPONENTS AND OPERATION 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 important task of receiving the output from sensors, analyzing it and taking the immediate required action. ECU is divided into an upper and lower portion. Lower portion contains the Electronic Circuit Board that processes all data whereas; upper portion contains the ignition coils for the spark plugs. Lower portion of each ECU contains two 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 by ECU no.2. If any problem is encountered with ECU no.1, cylinder no. 1 and 2 will be operated by ECU no. 2. This is the backup plan which has been mentioned earlier. The CADC (Central Air Digital Computer) consists of a analogue to digital converter, several quartz pressure sensors, and the microprocessor. Inputs to the system includes the primary flight controls, a number of switches, static and dynamic air pressure (for calculating stall points and aircraft speed) and a temperature gauge. 5

The output controls the primary flight controls, wing sweep and the flaps. FADEC sensor set are used to detect speed, cylinder head temperature, exhaust gas temperature, manifold air pressure, manifold air temperature, fuel pressure and throttle position. Health Status Annunciator(HSA) consists of five lights on panel and WOT .HSA provides information regarding the status of the FADEC system. Whenever, any problem is encountered, following warnings might pop up in FADEC windows: • FADEC WARN: Engine Failure may be imminent, more than one cylinder is affected, land ASAP • FADEC CAUTION: 99.9% of installed components are working. No prompt action is required. • PPWR FAIL: Primary Battery is not being charged, will be accompanied by EBAT FAIL, you will start draining both batteries and have at least 60 minutes to land. Your secondary battery will only power FADEC, AI, and Turn Coordinator • EBAT FAIL: Backup Battery not being charged, everything can run from Primary Power Source/Battery. • FUEL PUMP: illuminates when Fuel Boost Pump Mode Switch is in ON or OFF. If this light is illuminated it means that you are manually controlling the fuel pump or that the fuel pressure is out of the 20-40 psi range. Illuminates for electric driven fuel pump as well as engine driven pump. • WOT: It is situated below HSA panel. Illuminates when Throttle Position Switch (TPS) is contacted (full throttle), signal sent to ECU that max power is 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) and then to Electronic Control Units (ECUs) for data processing and analysis. Each ECUs has two Central Air Data computer (CADC) inputs. All the sensors mentioned above flow their outputs to CADC before they are sent to ECUs. There is 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 five sources: 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 inputs fail to operate, FADEC operates in alternative way. That is, FADEC takes the latest 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 thrust to decrease. After the detection of information, ECUs direct actuator to perform accordingly. The FADEC system continuously monitors fuel and ignition conditions. The ECU units receive information from sensors via the Low Voltage Harness which interfaces with the MPC units via 50-pin connectors. The status of the FADEC system is conveyed to the pilot by the HSA. Discrete lamps in the HSA will illuminate upon detection of system faults and during some normal control actions. Sensor input to each control channel includes engine speed, crank position, fuel pressure, intake manifold air pressure, intake manifold air temperature and Wide Open Throttle (WOT) position. In addition, each control channel also receives 7

exclusive signals for measuring its cylinder’s head temperature and exhaust gas temperature. The ECU units use the signals from sensors to determine the required fuel mixture and ignition timing for its cylinder’s next combustion event. The required fuel quantity is injected into each cylinder intake port at the appropriate time, with respect to crank position, by a solenoid style fuel injector. The injector’s control coil is driven directly by the associated control channel. FADEC systems are either powered by the aircrafts main electrical engine or from a separate generator connected to the engine. However, a backup source of 12 or 24 voltages is available for both the cases because failure of FADEC system could result in complete loss of engine thrust. To eliminate the loss of thrust, two separate and identical digital channels are installed which are capable of providing thrust to all engines. Two channels are housed in one assemble but are physically separated. FADEC comes with an impressive improvement to the electrical system. In the event 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 remains online supporting night time operations.

2.3

USE OF SENSOR IN FADEC

Sensor is a device that is designed to transform acoustic, biological, chemical, electrical, magnetic, mechanical, optical, radiation or thermal stimuli into an electrical signal for the purpose of transmitting information. Sensors and sensing techniques are needed to be integrated into the FADEC. This requires the addition of signal conditioners and software addition to the control algorithms. Signal conditioning of the signal may involve amplification, filtering, and may contain some. All the sensors need to be interfaced with the hardware through analog signal multiplexer and 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 sensors Control sensors are critical to maintaining stable engine operation including temperatures, pressures, and speed measurement. Feedback sensors are primarily position sensors for measurement and control of actuator position. Diagnostic sensors may include all control sensor types and additionally, vibration, strain, Infrared, and gas measurement. Control loops are required to maintain safe and stable engine operation. Each sensor is routed to a central Controller (FADEC). Todays manufacturer employs dedicated wiring for each measurement and actuation location. Figure 2.3 shows typical 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 information 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 MODERN AIRCRAFT 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 developed one after another.

Table 3: Use of FADEC in different Aircrafts Capable of controlling single or dual channel turboprops, turbo shafts, turbojets and turbofans, FADECs control the various actuators in real time by continuously processing and analyzing data collected by multiple sensors (oil, kerosene, engine, ignition, alternator, etc.). Equipped with a comprehensive set of built-in tests, FADECs are designed to resist severe environments (electromagnetic interferences, lightning, contaminations, vibrations, high temperatures, etc.) and offer lower costs of ownership. Featured in several programs such as CFM56, CF6, GE90, GEnx, TP400, GP7200 and SaM146 engines, Developed and built alongside 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 12

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

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Chapter 4

FUTURE ADVANCEMENT FADEC has been a boon to Aircraft. It has reduced concentration of pilots and increased efficiency by 15%. However, we can expect further advancement form the device in the future. FADEC are programmed by the manufacturer and the installed program varies for different engines. As it operates within the given code, pilot cannot override its decision, despite coming up with better solutions at times. Most importantly, the current centralized FADEC system must be replaced with distributed FADEC system. Distributed system will increase the life cycles of FADEC and would provide greater flexibility. NASA has been carrying out this research. 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 far better. They have been able to eliminate the need for magnetos, carburetor heat, mixture controls and engine priming as well. Due to presence of automatic sensing and optimum fuel supply, the system also proves to be advantageous in increasing fuel efficiency and overall performance of the engine. Moreover the best part of using FADEC is that the engine starts with a push of a button. The pilot gains more time and concentration since he is relieved from several responsibilities like leaning 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 system does not provide with manual override. Therefore the pilot has nothing to do than pray that the system performs reliably and according to he wishes. Although, research is being carried out, no solution has been obtained for centralized system. Despite these limitations, FADEC has been proved as a boon for Aircraft industries.

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Bibliography [1] Khan A. MD. (et al.) 2013. Experimental study of FADEC system on Lycoming engine. International Journal of Modern engineering Research [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 fail safe gas turbine engine controls, monitors and prognostics. Air force research laboratory.

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