FADEC
Encyclopedia
Full Authority Digital Engine (or Electronics) Control (FADEC) is a system consisting of a digital
computer
, called an electronic engine controller (EEC) or engine control unit
(ECU), and its related accessories that control all aspects of aircraft
engine
performance. FADECs have been produced for both piston engines and jet engines.
. By moving throttle levers directly connected to the engine, the pilot
or the flight engineer could control fuel
flow, power output, and many other engine parameters.
Following mechanical
means of engine control came the introduction of analog electronic
engine control. Analog electronic control varies an electrical signal to communicate the desired engine settings. The system was an evident improvement over mechanical control but had its drawbacks, including common electronic noise interference and reliability issues. Full authority analogue control was used in the 1960s and introduced as a component of the Rolls Royce Olympus 593 engine of the supersonic transport aircraft Concorde
. However, the more critical inlet control was digital on the production aircraft.
Following analog electronic control, the logical progression was to digital electronic control systems. Later in the 1970s, NASA
and Pratt and Whitney experimented with the first experimental FADEC, first flown on an F-111
fitted with a highly modified Pratt & Whitney TF30 left engine. The experiments led to Pratt & Whitney F100
and Pratt & Whitney PW2000
being the first military and civil engines, respectively, fitted with FADEC, and later the Pratt & Whitney PW4000
as the first commercial "dual FADEC" engine. The first FADEC in service was developed for the Harrier
II Pegasus
engine by Dowty
& Smiths Industries Controls
.
. 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.
FADEC works by receiving multiple input variables of the current flight condition including air density, throttle lever position, engine temperatures, engine pressures, and many other parameters. The inputs are received by the EEC and analyzed up to 70 times per second. Engine operating parameters such as fuel flow, stator vane position, bleed valve position, and others are computed from this data and applied as appropriate. FADEC also controls engine starting and restarting. The FADEC's basic purpose is to provide optimum engine efficiency for a given flight condition.
FADEC not only provides for efficient engine operation, it also allows the manufacturer to program engine limitations and receive engine health and maintenance reports. For example, to avoid exceeding a certain engine temperature, the FADEC can be programmed to automatically take the necessary measures without pilot intervention.
is provided in the form of two or more, separate identical digital channels. Each channel may provide all engine functions without restriction. FADEC also monitors a variety of analog, digital and discrete data coming from the engine subsystems and related aircraft systems, providing for fault tolerant engine control.
length, or cruise altitude, into the flight management system
(FMS). The FMS uses this data to calculate power settings for different phases of the flight. At takeoff, the flight crew advances the throttle to a predetermined setting, or opts for an auto-throttle takeoff if available. The FADECs now apply the calculated takeoff thrust setting by sending an electronic signal to the engines; there is no direct linkage to open fuel flow. This procedure can be repeated for any other phase of flight.
In flight, small changes in operation are constantly made to maintain efficiency. Maximum thrust is available for emergency situations if the throttle is advanced to full, but limitations can’t be exceeded; the flight crew has no means of manually overriding the FADEC.
has analyzed a distributed FADEC architecture rather than the current centralized, specifically for helicopters. Greater flexibility and lower life cycle costs are likely advantages of distribution.
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
, called an electronic engine controller (EEC) or engine control unit
Engine control unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
(ECU), and its related accessories that control all aspects of aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
engine
Engine
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
performance. FADECs have been produced for both piston engines and jet engines.
History
The goal of any engine control system is to allow the engine to perform at maximum efficiency for a given condition. The complexity of this task is proportional to the complexity of the engine. Originally, engine control systems consisted of simple mechanical linkages controlled by the pilot, but then evolved and became the responsibility of the third pilot-certified crew member, the flight engineerFlight engineer
Flight engineers work in three types of aircraft: fixed-wing , rotary wing , and space flight .As airplanes became even larger requiring more engines and complex systems to operate, the workload on the two pilots became excessive during certain critical parts of the flight regime, notably takeoffs...
. By moving throttle levers directly connected to the engine, the pilot
Aviator
An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...
or the flight engineer could control fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
flow, power output, and many other engine parameters.
Following mechanical
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...
means of engine control came the introduction of analog electronic
Analog device
Analog device is an apparatus that measures continuous information. The measured analog signal has an infinite number of possible values. The only limitation on resolution is the accuracy of the measuring device. Such apparatus operates with variables which are constituted by continuously measured...
engine control. Analog electronic control varies an electrical signal to communicate the desired engine settings. The system was an evident improvement over mechanical control but had its drawbacks, including common electronic noise interference and reliability issues. Full authority analogue control was used in the 1960s and introduced as a component of the Rolls Royce Olympus 593 engine of the supersonic transport aircraft Concorde
Concorde
Aérospatiale-BAC Concorde was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...
. However, the more critical inlet control was digital on the production aircraft.
Following analog electronic control, the logical progression was to digital electronic control systems. Later in the 1970s, NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
and Pratt and Whitney experimented with the first experimental FADEC, first flown on an F-111
General Dynamics F-111
The General Dynamics F-111 "Aardvark" was a medium-range interdictor and tactical strike aircraft that also filled the roles of strategic bomber, reconnaissance, and electronic warfare in its various versions. Developed in the 1960s by General Dynamics, it first entered service in 1967 with the...
fitted with a highly modified Pratt & Whitney TF30 left engine. The experiments led to Pratt & Whitney F100
Pratt & Whitney F100
-External links:* * *...
and Pratt & Whitney PW2000
Pratt & Whitney PW2000
|-See also:-External links:...
being the first military and civil engines, respectively, fitted with FADEC, and later the Pratt & Whitney PW4000
Pratt & Whitney PW4000
|-See also:-External links:* * *...
as the first commercial "dual FADEC" engine. The first FADEC in service was developed for the Harrier
Harrier Jump Jet
The Harrier, informally referred to as the Jump Jet, is a family of British-designed military jet aircraft capable of vertical/short takeoff and landing operations...
II Pegasus
Rolls-Royce Pegasus
The Rolls-Royce Pegasus is a turbofan engine originally designed by Bristol Siddeley, and now manufactured by Rolls-Royce plc. This engine is able to direct thrust downwards which can then be swivelled to power a jet aircraft forward. Lightly loaded, it can also manoeuvre like a helicopter,...
engine by Dowty
Dowty Group
Dowty Group was a leading British manufacturer of aircraft equipment. It was listed on the London Stock Exchange and was once a constituent of the FTSE 100 Index but was acquired by TI Group in 1992.-History:...
& Smiths Industries Controls
Smiths Group
Smiths Group plc is a global engineering company headquartered in London, United Kingdom. It has operations in over 50 countries and employs around 23,550 staff....
.
Function
True full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. If the engine is controlled digitally and electronically but allows for manual override, it is considered solely an EEC or ECUEngine control unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
. 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.
FADEC works by receiving multiple input variables of the current flight condition including air density, throttle lever position, engine temperatures, engine pressures, and many other parameters. The inputs are received by the EEC and analyzed up to 70 times per second. Engine operating parameters such as fuel flow, stator vane position, bleed valve position, and others are computed from this data and applied as appropriate. FADEC also controls engine starting and restarting. The FADEC's basic purpose is to provide optimum engine efficiency for a given flight condition.
FADEC not only provides for efficient engine operation, it also allows the manufacturer to program engine limitations and receive engine health and maintenance reports. For example, to avoid exceeding a certain engine temperature, the FADEC can be programmed to automatically take the necessary measures without pilot intervention.
Safety
With the operation of the engines so heavily relying on automation, safety is a great concern. RedundancyRedundancy (engineering)
In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
is provided in the form of two or more, separate identical digital channels. Each channel may provide all engine functions without restriction. FADEC also monitors a variety of analog, digital and discrete data coming from the engine subsystems and related aircraft systems, providing for fault tolerant engine control.
Applications
A typical civilian transport aircraft flight may illustrate the function of a FADEC. The flight crew first enters flight data such as wind conditions, runwayRunway
According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...
length, or cruise altitude, into the flight management system
Flight management system
A flight management system is a fundamental part of a modern airliner's avionics. An FMS is a specialized computer system that automates a wide variety of in-flight tasks, reducing the workload on the flight crew to the point that modern aircraft no longer carry flight engineers or navigators. A...
(FMS). The FMS uses this data to calculate power settings for different phases of the flight. At takeoff, the flight crew advances the throttle to a predetermined setting, or opts for an auto-throttle takeoff if available. The FADECs now apply the calculated takeoff thrust setting by sending an electronic signal to the engines; there is no direct linkage to open fuel flow. This procedure can be repeated for any other phase of flight.
In flight, small changes in operation are constantly made to maintain efficiency. Maximum thrust is available for emergency situations if the throttle is advanced to full, but limitations can’t be exceeded; the flight crew has no means of manually overriding the FADEC.
Advantages
- Better fuel efficiencyFuel efficiencyFuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...
- Automatic engine protection against out-of-tolerance operations
- Safer as the multiple channel FADEC computer provides redundancyRedundancy (engineering)In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
in case of failure - Care-free engine handling, with guaranteed thrustThrustThrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
settings - Ability to use single engine type for wide thrust requirements by just reprogramming the FADECs
- Provides semi-automatic engine starting
- Better systems integration with engine and aircraft systems
- Can provide engine long-term health monitoring and diagnostics
- Number of external and internal parameters used in the control processes increases by one order of magnitude
- Reduces the number of parameters to be monitored by flight crews
- Due to the high number of parameters monitored, the FADEC makes possible "Fault Tolerant Systems" (where a system can operate within required reliability and safety limitation with certain fault configurations)
- Can support automatic aircraft and engine emergency responses (e.g. in case of aircraft stall, engines increase thrust automatically).
Disadvantages
- Full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. In the event of a total FADEC failure, pilots have no way of manually controlling the engines for a restart, or to otherwise control the engine. As with any single point of failure, the risk can be mitigated with redundant FADECs.
- High system complexity compared to hydromechanical, analogue or manual control systems
- High system development and validation effort due to the complexity
Requirements
- Engineering processes must be used to design, manufacture, install and maintain the sensors which measure and report flight and engine parameters to the control system itself.
- Software engineering processes must be used in the design, implementation and testing of the software used in these safety-critical control systems. This requirement led to the development and use of specialized software such as SCADASCADASCADA generally refers to industrial control systems : computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:...
.
Research
NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
has analyzed a distributed FADEC architecture rather than the current centralized, specifically for helicopters. Greater flexibility and lower life cycle costs are likely advantages of distribution.
External links
- Harrier flies with digitally controlled Pegasus - a 1982 article in Flight InternationalFlight InternationalFlight International is a global aerospace weekly publication produced in the UK. Founded in 1909, it is the world's oldest continuously published aviation news magazine...
magazine - Active-control engines a 1988 Flight International article on FADEC engines