Aircraft Electrical and Electronic Systems continues the series of textbooks written for aircraft engineering students. This book addresses the electrical contents. Aircraft Electrical and Electronic Systems: Principles, Maintenance and Operation Fundamental Electrical and Electronic Principles, Third Edition. Read more. Aircraft Electrical and Electronic Systems: Principles, Maintenance and Operation [Mike Tooley BA; Advanced Technological and Higher National Certificates.
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Answers to multiple choice questions Appendix 4: Electrical quantities, symbols and units Appendix 5: Electrical formulae Appendix 6: Decibels Appendix 7: Wire and cable sizes Appendix 8: Electrical and electronic symbols Appendix Preface Aircraft Electrical and Electronic Systems continues the series of textbooks written for aircraft engineering students.
This book is designed to cover the essential knowledge base required by certifying mechanics, technicians and engineers engaged in engineering maintenance activities on commercial aircraft and in general aviation.
In addition, this book should appeal to members of the armed forces and others attending training and educational establishments engaged in aircraft maintenance and related aeronautical engi- neering programmes.
This book will also appeal to others within the aircraft industry who need an insight into electrical and electronic systems, e. The book provides an introduction to the funda- mentals of electrical, electronic and digital theory that underpins the principles of systems covered in the remainder of the book. For the reader that already has background knowledge of the fundamentals, the sub- sequent chapters can be read as individual subjects.
For the reader that requires a deeper understanding of related fundamentals, additional material can be found in related books in the series: The books in this series have been designed for both independent and tutor-assisted studies.
The series also provides a useful source of reference for those taking ab initio training pro- grammes in EASA Part and FAR approved organizations as well as those following related pro- grammes in further and higher education institutions. During the s, integrated computer-based systems were being devel- oped, e. The continued development and integration of electrical and electronic systems, together with the widespread use of integrated circuits, microproces- sors, data communications and electronic displays, have given new meaning to the term avionics.
Aircraft engineers will be exposed to in-service aircraft using older technology, together with the new aircraft enter- ing service based on modern technology. Using trends from the last 40 years, there will be an ever-increasing dependence on avionic systems. The eventual out- come could be the all-electric aircraft, a concept where traditional mechanical linkages, hydraulics and pneumatics are totally replaced by electrical and elec- tronic systems. This book establishes a reference point for engi- neering students; it does not attempt to address all system types for all aircraft types.
It is also impor- tant to note that this book does not attempt to provide the level of detail found in the aircraft publications, including the maintenance and wiring diagram manu- als. Each A summary of the book is as follows.
Chapter 1 sets the scene by providing an expla- nation of electricity in terms of the motion of elec- tric charge and basic electrical quantities such as current, voltage, resistance and power. The chapter provides an introduction to electrostatics and capaci- tors and also to electromagnetism and inductors.
Here the emphasis is on the key concepts and fundamen- tal laws that underpin the operation of the electri- cal systems found in aircraft. The chapter provides a detailed introduction to alternating current and trans- former principles, and concludes with an essential section on safety. This chapter will be particularly useful if you have not previously studied electrical principles.
Electronic fundamentals are introduced in Chapter 2. This chapter explains the principles, construction and basic application of a variety of common semi- conductor devices including diodes, thyristors, tran- sistors and integrated circuits. The advent of digital techniques and integrated cir- cuits has revolutionized the scope and applications for avionic systems. Chapter 3 provides readers with an introduction to digital techniques. The function and operation of logic gates are established before moving on to explore the use of combinational and sequen- tial logic in several typical aircraft applications.
The chapter also provides an overview of coding sys- tems and the logic systems that are used to represent numerical data. An introduction to aircraft data bus systems is provided together with a brief overview of the architecture and principal constituents of simple computer systems. Generators and motors are widely used in modern aircraft. Chapter 4 explains the principles on which they operate as well as the theoretical and practical aspects of aircraft power generation and distribution.
Three-phase systems and methods of connection are described in some detail. If you are in any doubt as to whether or not you should work through Chapters 1 to 4, you can always turn to the multiple choice questions at the end of each chapter to assess your knowledge. All electrical and electronic systems require a power source. Batteries are primary sources of elec- trical power found on most aircraft delivering direct current DC. Chapter 5 reviews the battery types used on aircraft, typical applications and how they are installed and maintained.
Other types of battery are being considered for primary power on aircraft; these include lithium and nickel-metal hydride. In Chapter 6, we review the other sources of elec- trical power used on aircraft and their typical applica- tions. Electrical power can be derived from a variety of sources; these are categorized as either primary or secondary sources. This power is either in the form of direct or alternating current depending on system require- ments.
Generators can either supply direct or alternat- ing current AC ; the outputs of generators need to be regulated. Inverters are used to convert DC usually from the battery into alternating AC. In addition to onboard equipment, most aircraft have the facil- ity to be connected to an external power source dur- ing servicing or maintenance. While the aircraft is on the ground, the APU can also provide electrical power. In the event of generator failure s , continuous power can be provided by a ram air tur- bine RAT.
The safe and economic operation of an aircraft is becoming ever more dependent on electrical and electronic systems. These systems are all intercon- nected with wires and cables; these take many forms. Chapter 7 describes the physical construction of wires and cables together with how they are protected from overload conditions before power is distributed to the various loads on the aircraft.
Electrical wires and cables have to be treated as an integral part of the aircraft requiring careful installation; this is fol- lowed by direct ongoing inspection and maintenance requirements for continued airworthiness. Wire and System reliability will be seriously affected by wiring that has not been correctly installed or maintained. Legislation is being proposed to introduce a new term: EWIS relates to any wire, wiring device, or combination of these, including termination devices, installed in the air- craft for transmitting electrical energy between two or more termination points.
Electrical power is supplied to the various loads in the aircraft via common points called busbars. The electrical power distribu- tion system is based on one or more busbar s ; these provide pre-determined routes to circuits and com- ponents throughout the aircraft. The nature and com- plexity of the distribution system depend on the size and role of the aircraft, ranging from single-engine general aviation through to multi-engine passenger transport aircraft.
Aircraft Electrical Systems
There also needs to be a means of protecting the power source and feeder lines to the busbar, i. Chapter 9 describes generic controls and transducer devices used on aircraft.
A switch provides the simplest form of circuit control and monitoring. Switches can be operated manu- ally by a person, activated by sensing movement, or controlled remotely.
Many other aircraft parameters need to be measured; this is achieved by a variety of transducers; these are devices used to convert the desired parameter, e. The aircraft engine is installed with many sys- tems requiring electrical power. Chapter 10 describes engine starting, ignition and indicating system for both piston and gas turbine engines.
The predomi- nant electrical requirement in terms of current con- sumption is for the engine starting system. General aviation aircraft use electrical starter motors for both piston and gas turbine engines; larger transport air- craft use an air-start system controlled electrically derived from ground support equipment or by air cross-fed from another engine.
Electrical starting sys- tems on piston and gas turbine engines are very dif- ferent. The trend towards the all-electric aircraft will see more aircraft types using electrical starting meth- ods. The engine also requires electrical power for the ignition system; once again, the needs of piston and gas turbine engines are quite different.
Although start- ing and ignition systems are described in this chapter as separate systems, they are both required on a co- ordinated basis, i. Electrical and electronic requirements for engines also include the variety of indicating systems required to operate and manage the engine.
These indicating systems include but are not limited to the meas- urement and indication of: Indications can be provided by individual indicators or by electronic displays. The management of fuel is essential for the safe and economic operation of the aircraft. The scope of fuel management depends on the size and type of air- craft; fuel is delivered to the engines using a variety of methods.
Chapter 11 provides an overview of fuel management on a range of aircraft types. The system typically comprises fuel quantity indication, distribu- tion, refuelling, defuelling and fuel jettison. Various technologies and methods are used to measure fuel quantity: Technologies range from sight gauges through to electronic sensors.
On larger aircraft, fuel is fed to the engines by electrically driven pumps. On smaller aircraft, an engine-driven pump is used with electrical pumps used as back-up devices. Solenoid or motorized valves are used to iso- late the fuel supply to engines under abnormal condi- tions. On larger aircrafts, the fuel can be transferred Lighting is installed on aircraft for a number of reasons including: The applications of aircraft lights can be broadly grouped into four areas: Typical applications for this equipment includes lighting, audio and visual systems.
Chapter 13 describes the many types of systems and equipment used for passen- ger safety, convenience and entertainment. These announcements are made from hand-held microphones and are heard over loudspeakers in the cabin and passenger head- sets. The same system can be used to play automatic sound tracks; this is often used for announcements in foreign languages, or to play background music dur- ing boarding and disembarkation.
A range of galley equipment is installed on business and passenger aircraft. The nature of this equipment depends on the size and role of the aircraft. Chapter 14 reviews airframe systems such as landing gear control and indication, control surface position and indicating systems.
Various sensors are needed for the monitoring and control of airframe systems. Two-state conditions include: Variable positions include: Micro-switches or proximity sen- sors detect two-state positions; variable position devices are detected by a variety of devices including synchros and variable resistors. Chapter 15 describes a variety of systems installed on aircraft to protect them from a variety of hazards including: Stall protection systems provide the crew with a clear and distinctive warning before an unsafe condition is reached.
The anti-skid system also called an anti-lock braking system: ABS is designed to prevent the main landing gear wheels from locking up during landing, particu- larly on wet or icy runway surfaces.
Chapter 17 describes the generic name given to this type of protection: With CFIT, the pilots are generally unaware of this situation until it is too late. This system was further developed into the enhanced ground proximity warning system EGPWS by adding a forward-looking terrain avoid- ance FLTA feature, made possible via global posi- tioning system technology.
Flight data recorders used for accident investigation are man- datory items of equipment in commercial transport aircraft. Data recorders can also be used to indicate trends in aircraft and engine performance.
These algo- rithms include engine parameters such as engine exhaust temperature, oil pressure and shaft vibration for given speeds and altitudes. One of the consequences of operating electrical and electronic equipment is the possibility of disturb- ing, or interfering with, nearby items of electronic equipment.
The term given to this type of disturbance is electromagnetic interference EMI. Electrical or electronic products will both radiate and be suscep- tible to the effects of EMI. This is a paradox since many principles of electrical engineering are based on electromagnetic waves coupling with conductors to produce electrical energy and vice versa generators and motors.
The ability of an item of equipment to operate alongside other items of equip- ment without causing EMI is electromagnetic com- patibility EMC. Modern digital equipment operates at very high speed and relatively low power levels. These advances are primarily due to the reduction in the physical size of semiconductor junctions; this leads to higher-density components in given size of integrated circuit. Effects range from weakening of semiconduc- tor junctions through total failure of the equipment; both these effects can occur without any visible signs of damage to the naked eye!
Electrostatic sensitive devices ESSD are electronic components that are prone to damage from stray electrical charge pro- duced primarily from human operators. This problem is particularly prevalent with high-density memory devices and electronic displays.
Weakening and dam- age to static-sensitive devices can result from mis- handling and inappropriate methods of storage; the practical issues for handling ESSD are addressed in Chapter The generic term for this range of processes is continuing airworthiness. Chapter 20 reviews some practical installation requirements, documentation and test equipment required by the avionics engineer to ensure the continued airworthi- ness of aircraft electrical and electronic systems. Persons responsible for the release of an aircraft or a component after maintenance are the certifying staff.
Maintenance of an aircraft and its Acknowledgements The authors would like to express their thanks to the following persons for ideas, support and contribu- tions to the book.
We thank Lloyd Dingle, who had the original idea for the aircraft engineering series, and Alex Hollingsworth for commissioning this book. Thanks also to the following organizations for per- mission to reproduce their information: This chapter will provide you with an introduction to the essential electrical theory that underpins the rest of this book.
However, if you are in any doubt as to whether or not you should work through this chapter you can always turn to Section 1.
In order to understand something about the nature of electrical charge we need to consider a simple model of the atom. This model, known as the Bohr model see Fig. Within the nucleus there are protons which are positively charged and neutrons which, as their name implies, are electrical neutral and have no charge. Orbiting the nucleus are electrons that have a nega- tive charge, equal in magnitude size to the charge on the proton.
6 editions of this work
These electrons are approximately two thousand times lighter than the protons and neutrons in the nucleus. In a stable atom the number of protons and elec- trons are equal, so that overall, the atom is neutral and has no charge.
However, if we rub two particular materials together, electrons may be transferred from one to another. This alters the stability of the atom, leaving it with a net positive or negative charge.
When an atom within a material loses electrons it becomes positively charged and is known as a positive ion, when an atom gains an electron it has a surplus nega- tive charge and so is referred to as a negative ion. These differences in charge can cause electrostatic effects. For example, combing your hair with a nylon comb may result in a difference in charge between your hair and the rest of your body, resulting in your hair standing on end when your hand or some other differently charged body is brought close to it.
The number of electrons occupying a given orbit within an atom is predictable and is based on the position of the element within the periodic table. The electrons in all atoms sit in a particular orbit, or shell, dependent on their energy level. Electrical fundamentals 1 Chapter Figure 1. Aircraft electrical and electronic systems2 All electrons and protons carry an electrostatic charge but its value is so small that a more conven- ient unit of charge is needed for practical use which we call the coulomb.
One coulomb C is the total amount of the charge carried by 6. Thus a single electron has a charge of a mere 1. Examples of good conductors include aluminium, copper, gold and iron. Figure 1. A small amount of external energy is required to overcome the attraction of the nucleus. The atom once detached from the atom is able to move freely around the structure of the material and is called a free electron. It is these free electrons that become the charge carriers within a material.
Materials that have large numbers of free electrons make good conductors of electrical energy and heat. In a material containing free electrons their direc- tion of motion is random, as shown in Fig.
Metals are the best conductors, since they have a very large number of free electrons available to act as charge carriers. Materials that do not conduct charge are called insulators; their electrons are tightly bound to the nuclei of their atoms.
Examples of insulators include plastics, glass, rubber and ceramic materials. For example, heat is produced when an electric current is passed through a resistive heating element.
Key point Electrons each carry a tiny amount of negative electrical charge. Test your understanding 1. Explain the following terms: State, with reasons, whether an insulator or conductor is required in each of the following applications: Indeed, many of the everyday items that we use in the home and at work rely for their operation on the existence of electric charge and the ability to make that charge do some- thing useful.
Electric charge is also present in the natural world and anyone who has experienced an electrical storm cannot fail to have been awed by its effects. In this section we begin by explaining what electric charge is and how it can be used to produce conduction in solids, liquids and gases. If, on the other hand, it has a surplus of elec- trons, it will exhibit a net positive charge.
An imbal- ance in charge can be produced by friction removing or depositing electrons using materials such as silk and fur, respectively or induction by attracting or repelling electrons using a second body which is respectively positively or negatively charged. If two bodies have charges with the same polarity i. If, on the other hand, the charges on the two bodies are unlike i. From this we can con- clude that like charges repel and unlike charges attract.
Static charges can be produced by friction. In this case, electrons and protons in an insulator are separated from each other by rubbing two materials together in order to produce opposite charges. These charges will remain separated for some time until they eventually leak away due to losses in the insu- lating dielectric material or in the air surrounding the materials.
Note that more charge will be lost in a given time if the air is damp. These are known as static dischargers or static wicks — see Fig. Key point Charged bodies with the same polarity repel one another whilst charges with opposite polarity will attract one another. Where this might be a prob- lem steps are taken to dissipate the charge instead of allowing it to accumulate uncontrolled.
Key maintenance point Stray static charges can very easily damage static- sensitive devices such as semiconductors, mem- ory devices and other integrated circuits. Damage can be prevented by adopting the appropriate electrostatic sensitive device ESD precautions described in the aircraft maintenance manual when handling such devices.
Precautions usually involve using wrist straps and grounding leads as well as using static-dissipative packaging materials. The electric Figure 1. Figures 1. The amount of charge that can be stored by a capacitor is given by the relationship: This Figure 1. If the plates are sepa- rated by a distance of 21mm determine the potential difference that exists between the plates. V Example 1. What charge is present?
The charge can be calculated from: Example 1.
What voltage should be applied to the capacitor? The voltage can be calculated from: It is also essential to observe the correct polarity when replacing an electro- lytic polarized component.
This is usually clearly marked on the external casing.
Key maintenance point When working with high-voltage capacitors it is essential to ensure that the capacitor is fully dis- charged before attempting to replace the component.
In most cases, any accumulated charge will safely drain away within a few seconds after removal of power. Aircraft electrical and electronic systems6 Test your understanding 1. The two plates of a parallel plate capacitor are separated by a distance of 15mm. If the plates are separated by a distance of 2. DC circuits are found in every aircraft.
An understanding of how and why these circuits work is an essential prerequisite to understanding more com- plex circuits. However, when we indicate the direction of current in a circuit we show it as moving from a point that has the great- est positive potential to a point that has the most nega- tive potential.
The most commonly used method of generat- ing direct current is the electrochemical cell. A cell is a device that produces a charge when a chemical reaction takes place. When several cells are connected together they form a battery. There are two types of cell: Primary cells produce electrical energy at the expense of the chemicals from which they are made and once these chemicals are used up, no more elec- tricity can be obtained from the cell.
In secondary cells, the chemical action is reversible. This means that the chemical energy is converted into electrical energy when the cell is discharged whereas electrical energy is converted into chemical energy when the cell is being charged. Key point In a primary cell the conversion of chemical energy to electrical energy is irreversible and so these cells cannot be recharged.
In secondary cells, the con- version of chemical energy to electrical energy is reversible. Thus these cells can be recharged and reused many times. Explain the difference between a primary and a secondary cell. One ampere is equal to one coulomb C per second, or:What e.
However, if you are in any doubt as to whether or not you should work through this chapter you can always turn to Section 1. With the Onex panel being so small and not much room for a transponder I also like that my transponder is located behind my seat and I can operate it from my Skyview. Formato PDF. Mark Hammar October 18, Early on, when you are implementing a Quality Management System QMS using the requirements of ISO , you will need to talk to a certification body to find out what you need to do to certify your management system as compliant with the requirements.
Energy can be converted from one form to another. The loop is broken between the source V1 , the input to the loop and the capacitor tap, V1p, the output of the loop. Prerequisites: You are assumed to have completed ECE and theref ore to have a basic understanding of electromagnetic wave propagation and antenna radiation.