FADEC-Full Authority Digital Engine Control

FADEC is a system comprising of a digital computer (Electronic Engine Control EEC) and the other accessories that control all the aspects of aircraft engine performance. FADEC is made for piston engine and jet engines both but they differ in the way of controlling the engine. A primary reason for the rapid technological progress of the U. S. LCA industry has been its ability to draw on and benefit from innovations in other high-technology industries. For example, high speed supercomputers accurately model aircraft airflows without the aid of wind tunnels.

Computers also have been incorporated significantly in LCA cockpits as integrators of information. With the increased usage of flat-panel displays that project the image of an electromechanical gauge, several displays either can be transferred individually to various panels or superimposed on one panel at the pilot's discretion. In addition, computers have aided in the development of Full-Authority Digital Engine Control (FADEC) systems. FADEC allows for improved monitoring and adjusting of engine operating parameters, such as fuel flow and speed.

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This enhanced control of aircraft engines has led to a decrease in both fuel consumption and maintenance demands. History of FADEC A FADEC (Full Authority Engine Control) is an electronic system that controls all the crucial parameters of aircraft power plants. One of the system roles is to lower the cognitive load of pilots while they operate turbojet engines, and to reduce the occurrence of pilot errors. The aim of any control system is to allow the engine to perform at the maximum capacity for a condition.

The original engine control system is mechanical linkages and controlled by the pilot.

By using throttle levers which are connected to the engine, the pilot could simply control power output, fuel flow, and the other parameters of engine. These mechanical means of engine control was an introduction of analog electronic engine control. Analog electronic control varies an electronic signal to communicate the desired engine settings. This system was first introduced as an essential part of the Rolls Royce Olympus 593 engine. The 593 engine was regarded best for the famous supersonic transport aircraft, Concord.

In the 1970's NASA and Pratt and Whitney first experimented on FADEC, it was first flown on F-111 fitted with highly modified Pratt and Whitney TF30 left engine. The experiments led to Pratt & Whitney F100 and Pratt & Whitney PW2000 being the first civil and military engines respectively fitted with FADEC and later the Pratt & Whitney PW4000 as the commercial "Duel FADEC" engine. Rolls- Royce funds almost 20 UTCs working on key areas of engine technology. Most of the UTCs focus on aspects of production technology, e. g. high temperature materials and combustion.

The York UTC is relatively unusual in that if focuses on process issues. In particular the York UTC investigates systems and software engineering processes for the development of full Authority Digital Engine Controllers (FADECs). A FADEC is a complex hydro-mechanical system which carries out all key engine control functions, typically: Thrust provision- altering fuel and air flows through the engine to provide managed thrust. Thrust control- in particular provision of reverse thrust from the engine for braking on landing.

Heat management- ensures that parts of the engine are cooled appropriately. Airframe communication- receiving control commands from the airframe (e. g. from the pilot) and returning engine status indications. Fault management- detecting faults in the engine status indications. (Henderson, pg. 38) Maintenance- recording faults data for on ground engine maintenance. At the heart of the FADEC is a computer system known as an Electronic Engine Controller (EEC). The EEC and its software form a hard real-time system and, typically, the system is safety critical, i.

e. failures could potentially lead to a loss of thrust and perhaps of the aircraft. Functions of FADEC-Full-Authority Digital Engine Control There must not be any form of manual override available for Full Authority Digital Engine Control. This fully places full authority upon the operating parameters of the engine to computer. If FADEC would fail the engine would also fail. If the engine would be controlled digitally and electronically, it would be considered as Electronic Control Unit (ECU) or Electrical Engine control (EEC).

FADEC works by the given input variables of the current flight position like engine temperatures, air density, engine pressures, throttle lever position and others. The EEC receives inputs and analyzes them up to 70 times per second. Engine operates many parameters like bleed valve position, stator vane position, and fuel flow and others are computed from this data and applied as appropriate. FADEC controls most of the functions like restarting and starting. The basic purpose of FADEC is to give optimum engine efficiency for a given flight condition.

FADEC allows receiving engine maintenance reports and program engine limitations. For instance, FADEC can be programmed to take the necessary measures without pilot intervention to avoid exceeding an engine temperature. Turbine engines The fuel control system on the turbine engine is fairly complex, as it monitors and adjusts many different parameters on the engine. These adjustments are done automatically and no action is required of the pilot other than starting and shutting down.

No mixture adjustment is necessary, and operation is fairly simple as far as the pilot is concerned. New generation fuel controls incorporate the use of a full authority digital engine control (FADEC) computer to control the engine's fuel requirements. The FADEC systems increase efficiency, reduce engine wear, and also reduce pilot workload. The FADEC usually incorporates back-up systems in the events computer failure. Jet engines Modern jet engine is very considerable: it forms an integral part of the engine and is essential for its operation.

In many cases some of the engine control electronics is physically mounted on the engine. Many modern jet engines have a full authority digital engine control system (FADEC). This automatically controls the flow of fuel to the engine combustion chambers by the fuel control unit so as to provide a closed loop control of engine thrust in response to the throttle command. The control system ensures the engine limits in terms of temperatures, engine speeds and that the accelerations are not exceeded and the engine responds in an optimum manner to the throttle command.

The system has what is known as full authority in terms of the control it can exercise on the engine and the high integrity failure survival control system is essential. Otherwise a failure in the system could seriously damage the engine and hazard the safety of the aircraft. A FADEC engine control system is thus similar in many ways to a FBW flight control system. (Collinson, pg. 9) FADEC is used in almost all jet engines and new piston engines on helicopter and fixed winged aircraft. With the operation of the engines so heavily relying on automation, the most important concern is its safety.

Redundancy is provided in the separate identical digital channels. FADEC monitors a discrete and digital data coming from the engine subsystems and variety of analog, and providing for fault tolerant engine control. In the civilian transport aircraft flight, the flight crew enters the appropriate data to the day's flight in the (FMS) flight management system. The FMS reads the data like wind, runway length, cruise altitude etc. and then calculates the settings for the different phases of flight. The flight crew advances the throttle to take off which contains no mechanical linkage to the engine.

The flight crew checks that they have merely sent an electronic signal to the engines as no direct linkage has been moved to open fuel flow. This is the same phase for all type of flights like cruise, climb etc. The FADECs compute and apply the appropriate trust setting. During the flight small changes in operation are being made to maintain efficiency. Full Authority Digital Control (FADEC) system is configured to ensure safe, stable and reliable engine operation at all the points in the flight envelope. Control laws are essential for providing the desired engine operations safely.

The control laws must be verified and validated before the engine starts for a flight. Reference Collinson, G, P, R. (2003) Introduction to Avionics Systems. Springer, pg. 9 Global Competitiveness of U. S. Advances-Technology Manufacturing Industries, DIANE Publishing Company, Darby. Henderson, Peter. System Engineering for Business Process Change: New Directions: Collected…pg. 38 Sullerey, K, R. Oommen, Charlie. Raghunandan, N,B. (2004 ). Air Breathing Engines and Aerospace Propulsion Proceedings of NCABE 2004.