GMR Aero School of Aviation Basic Aircraft Maintenance Training Manual PDF

GMR Air Cargo and Aerospace Engineering Limited, Hyderabad, Telangana, India. Website: www.gmrschoolofaviation.com Email: [email protected] BASIC AIRCRAFT MAINTENANCE...

GMR Air Cargo and Aerospace Engineering Limited, Hyderabad, Telangana, India. Website: www.gmrschoolofaviation.com Email: [email protected] BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL MODULE 3 - ELECTRICAL FUNDAMENTAL SUBMODULE 3.2 – STATIC ELECTRICITY AND CONDUCTION CATEGORY: B1.1/B2/B1.1+B2 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 1 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 1.2 ELECTROSTATIC BALLOON........................................................... 8 TABLE OF CONTENTS 1.3 EBONITE ROD.................................................................................. 8 FOREWORD.................................................................................................... 3 2. ELECTROSTATIC LAWS OF ATTRACTION AND REPULSION................. 9 COPYRIGHT NOTICE...................................................................................... 3 3. UNITS OF CHARGE................................................................................... 10 BASIC KNOWLEDGE REQUIREMENTS........................................................ 4 4. COULOMB’S LAW...................................................................................... 11 KNOWLEDGE LEVELS – CATEGORY A, B1, B2, B3 AND C AIRCRAFT MAINTENANCE LICENCE............................................................................... 5 5. ELECTROSTATIC FIELD........................................................................... 12 LEVEL 1........................................................................................................ 5 6. ESD CONSIDERATIONS........................................................................... 15 LEVEL 2........................................................................................................ 5 7. CONDUCTION OF ELECTRICITY............................................................. 16 LEVEL 3........................................................................................................ 5 7.1 CONDUCTION OF ELECTRICITY IN SOLIDS.................................... 16 ABBREVIATIONS............................................................................................. 6 7.2 CONDUCTION OF ELECTRICITY IN LIQUID...................................... 17 1. STATIC ELECTRICITY & DISTRIBUTION OF ELECTROSTATIC 7.3 CONDUCTION OF ELECTRICITY IN GASES..................................... 18 CHARGES........................................................................................................ 7 7.4 CONDUCTION OF ELECTRICITY IN VACUUM.................................. 19 1.1 STATIC ELECTRICITY EXPERIMENTS.......................................... 7 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 2 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION FOREWORD It is important to note that the information in this book is for study/ training purposes only and no revision service will be provided to the holder. When carrying out a procedure/ work on aircraft/ aircraft equipment you must always refer to the relevant aircraft maintenance manual or equipment manufacturer's handbook. For health and safety in the workplace you should follow the regulations/ guidelines as specified by the equipment manufacturer, your company, national safety authorities and national governments. COPYRIGHT NOTICE © Copyright. All worldwide rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form by any other means whatsoever: i.e., photocopy, electronic, mechanical recording or otherwise without the prior written permission of GMR School of Aviation. ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 3 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION BASIC KNOWLEDGE REQUIREMENTS These Study Notes comply with the syllabus of DGCA Regulation, CAR-66 (Appendix I) and the associated Knowledge Levels as specified. These Study Notes comply with the syllabus of EASA Regulation (EU) No. 1321/2014 Annex (Part-66) Appendix I and the associated Knowledge Levels as specified below: Level CAR 66/ Objective PART 66 Reference B1.1 B2 Static Electricity and Conduction Static electricity and distribution of electrostatic charges; Electrostatic laws of attraction and repulsion; 3.2 2 2 Units of charge, Coulomb's Law; Conduction of electricity in solids, liquids, gases and in vacuum. ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 4 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION KNOWLEDGE LEVELS – CATEGORY A, B1, B2, B3 AND C AIRCRAFT MAINTENANCE LICENCE Basic knowledge for categories A, B1, B2 and B3 are indicated by the allocation of knowledge levels indicators (1, 2 or 3) against each application subject. Category C applicants must meet either the category B1 or the category B2 basic knowledge levels. The knowledge level indicators are defined as follows: LEVEL 1 A familiarization with the principal elements of the subject. Objectives: The applicant should be familiar with the basic elements of the subject. The applicant should be able to give a simple description of the whole subject, using common words and examples. The applicant should be able to use typical terms. LEVEL 2 A general knowledge of the theoretical and practical aspects of the subject. An ability to apply that knowledge. Objectives: The applicant should be able to understand the theoretical fundamentals of the subject. The applicant should be able to give a general description of the subject using, as appropriate, typical examples. The applicant should be able to use mathematical formulae in conjunction with physical laws describing the subject. The applicant should be able to read and understand sketches, drawings and schematics describing the subject. The applicant should be able to apply his knowledge in a practical manner using detailed procedures. LEVEL 3 A detailed knowledge of the theoretical and practical aspects of the subject. A capacity to combine and apply the separate elements of knowledge in a logical and comprehensive manner. Objectives: The applicant should know the theory of the subject and interrelationships with other subjects. The applicant should be able to give a detailed description of the subject using theoretical fundamentals and specific examples. The applicant should understand and be able to use mathematical formulae related to the subject. The applicant should be able to read, understand and prepare sketches, simple drawings and schematics describing the subject. The applicant should be able to apply his knowledge in a practical manner using the manufacturer’s instructions. The applicant should be able to interpret results from various sources and measurements and apply corrective action where appropriate. ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 5 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION ABBREVIATIONS ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 6 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 1. STATIC ELECTRICITY & DISTRIBUTION OF ELECTROSTATIC 1.1 STATIC ELECTRICITY EXPERIMENTS CHARGES To perceive the existence of static electricity, simply rub a plastic ruler Electricity is often described as being either static or dynamic. The with a dry cloth and then bring it close to small pieces of paper (Like difference between the two is based simply on whether the electrons are confetti). at rest (static) or in motion (dynamic). Static electricity is a build-up of an The pieces of paper will stick to the ruler. electrical charge on the surface of an object. It is considered "static" due to the fact that there is no current flowing as in AC or DC electricity. Rubbing has charged the ruler with electricity (this is called Static electricity is usually caused when non-conductive materials such electrification). as rubber, plastic or glass are rubbed together, causing a transfer of This charge creates an attraction when we bring an electrified object electrons, which then results in an imbalance of charges between the near to another object that is not charged. two materials. The fact that there is an imbalance of charges between the two materials means that the objects will exhibit an attractive or The attraction lasts only for a short period of time, as the object (the repulsive force. ruler) dischargers its electricity. When we rub certain materials together, the surface electrons can The same phenomenon can be observed when we rub a glass rod with separate from the atoms of one material and attach to the atoms of the a silk cloth. The rod becomes positively charged because its atoms lose other. electrons to the silk. The second material will then have a surplus of electrons and be A high static charge can generate a mirror image of the charge with negatively charged, while the first material will have a shortage of reverse polarity on a surrounding element. electrons and be charged with static electricity. This transfer of charges between two materials can take place in different ways. This electrostatic phenomenon is called triboelectricity (from the Greek word tribe in, (“to rub”) ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 7 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 1.2 ELECTROSTATIC BALLOON 1.3 EBONITE ROD To illustrate this, think of a balloon that a child has rubbed (and therefore Rub an ebonite (or resin) rod with a silk cloth. We observe that the charged) before allowing it to fly away full this balloon will stick to a wall. rubbed part attracts light bodies such as small pieces of paper, pith balls, The negative charge in the balloon creates a positive image on the wall etc. and the force of attraction due to polarity differences causes the 2 The body is said to have been electrified by rubbing. objects to be attracted to each other, and the balloon sticks to the wall. Any experiment fails if we rub a hand-held metal rod, such as a copper rod, under similar conditions. It is successful if we hold the rod using an ebonite handle: in this case, we observe that this metal body attracts lightweight bodies not only with the part of its surface that was ribbed but with its entire surface. To interpret these facts, we observe that rubbing has developed something on the surface of the rubbed bodies that the ancient Greeks called “electron”. Every electrified body therefore carries a certain amount of electricity or, a certain electric charge. Figure 1 Figure 2 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 8 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 2. ELECTROSTATIC LAWS OF ATTRACTION AND REPULSION One of the most fundamental laws of static electricity, as well as magnetics, deals with attraction and repulsion. Like charges repel each other and unlike charges attract each other. All electrons possess a negative charge and as such will repel each other. Similarly, all protons possess a positive charge and as such will repel each other. Electrons (negative) and protons (positive) are opposite in their charge and will attract each other. For example, if two pith balls are suspended, as shown in Figure 3, and each ball is touched with the charged glass rod, some of the charge from the rod is transferred to the balls. The balls now have similar charges and, consequently, repel each other as shown in part B of Figure 3. If a plastic rod is rubbed with fur, it becomes negatively charged and the fur is positively charged. By touching each ball with these differently charged sources, the balls obtain opposite charges and attract each other as shown in part C of Figure 3. Coulomb's law further defines the relationship between charges. It states that like charges repel and opposite charges attract with a force proportional to the product of the charges and inversely proportional to the square of the distance between them. This means that objects with greater charge repel similar charges and attract opposite charges with greater force. Also, as the distance between charges becomes greater, the repulsion or attraction between the charges decreases. Figure 3 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 9 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 3. UNITS OF CHARGE A method of charging a metal bar by induction is demonstrated in Figure 5. A positively charged rod is brought near, but does not touch, an A single elementary charge (e) is the charge that a single proton (or uncharged metal bar. Electrons in the metal bar are attracted to the end electron) possesses. The coulomb (C) is an SI derived unit of electrical of the bar nearest the positively charged rod, leaving a deficiency of charge. One coulomb is equal to the charge carried by one ampere in electrons at the opposite end of the bar. If this positively charged end is one second. An ampere represents the flow of 6.241 × 1018 electrons. touched by a neutral object, electrons will flow into the metal bar and Although most objects become charged with static electricity by means neutralize the charge. The metal bar is left with an overall excess of of friction, a charged substance can also influence objects near it by electrons. contact. This is illustrated in Figure 4. If a positively charged rod touches an uncharged metal bar, it will draw electrons from the uncharged bar to the point of contact. Some electrons will enter the rod, leaving the metal bar with a deficiency of electrons (positively charged) and making the rod less positive than it was or, perhaps, even neutralizing its charge completely. Figure 4 Figure 5 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 10 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 4. COULOMB’S LAW Between two-point charges q and q’, separated in vacuum by a distance d, opposite forces F1 and F2 are exerted, and their intensity is given by the relationship: ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 11 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 5. ELECTROSTATIC FIELD Figure 7 illustrates the field around bodies having like charges. Positive charges are shown, but regardless of the type of charge, the lines of A field of force exists around a charged body. This field is an electrostatic force would repel each other if the charges were alike. The lines field (sometimes called a dielectric field) and is represented by lines terminate on material objects and always extend from a positive charge extending in all directions from the charged body and terminating where to a negative charge. These lines are imaginary lines used to show the there is an equal and opposite charge. direction a real force takes. To explain the action of an electrostatic field, lines are used to represent the direction and intensity of the electric field of force. As illustrated in Figure 6, the intensity of the field is indicated by the number of lines per unit area, and the direction is shown by arrowheads on the lines pointing in the direction in which a small test charge would move or tend to move if acted upon by the field of force. Either a positive or negative test charge can be used, but it has been arbitrarily agreed that a small positive charge will always be used in determining the direction of the field. Thus, the direction of the field around a positive charge is always away from the charge, as shown in Figure 6, because a positive test charge would be repelled. On the other hand, the direction of the lines about a negative charge is toward the Figure 7 (Field around two positively charged bodies) charge since a positive test charge is attracted toward it. Figure 6 (Direction of electric field around positive and negative charges) ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 12 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION It is important to know how a charge is distributed on an object. Figure Another example, shown in Figure 9, is the charge on a hollow sphere. 8 shows a small metal disk on which a concentrated negative charge Although the sphere is made of conducting material, the charge is evenly has been placed. By using an electrostatic detector, it can be shown that distributed over the outside surface. The inner surface is completely the charge is spread evenly over the entire surface of the disk. Since the neutral. This phenomenon is used to safeguard operating personnel of metal disk provides uniform resistance everywhere on its surface, the the large Van de Graaff static generators used for atom smashing. The mutual repulsion of electrons will result in an even distribution over the safest area for the operators is inside the large sphere, where millions entire surface. of volts are being generated. Figure 8 (Even Distribution of charge on metal disk) Figure 9 (Charge on a hollow sphere) ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 13 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION The distribution of the charge on an irregularly shaped object differs from that on a regularly shaped object. Figure 10 shows that the charge on such objects is not evenly distributed. The greatest charge is at the points, or areas of sharpest curvature, of the objects Figure 10 (Charge on irregularly shaped objects) ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 14 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 6. ESD CONSIDERATIONS 5. Do not try components to be off a circuit board. 6. Power must be removed from a circuit before replacing a component. One of the most frequent causes of damage to a solid-state component or integrated circuits is the electrostatic discharge (ESD) from the human 7. When using test probes on equipment and the space between the test body when one of these devices is handled. Careless handling of line points is very close, keep the exposed portion of the leads as short as replaceable units (LRUs), circuit cards, and discrete components can possible to prevent shorting. cause unnecessarily time consuming and expensive repairs. This damage can occur if a technician touches the mating pins for a card or box. Other sources for ESD can be the top of a toolbox that is covered with a carpet. Damage can be avoided by discharging the static electricity from your body by touching the chassis of the removed box, by wearing a grounding wrist strap, and exercising good professional handling of the components in the aircraft. (shown in Figure 11) This can include placing protective caps over open connectors and not placing an ESD sensitive component in an environment that will cause damage. Parts that are ESD sensitive are typically shipped in bags specially designed to protect components from electrostatic damage. Other precautions that should be taken with working with electronic components are: 1. Always connect a ground between test equipment and circuit before attempting to inject or monitor a signal. Figure 11 2. Ensure test voltages do not exceed maximum allowable voltage for the circuit components and transistors. 3. Ohmmeter ranges that require a current of more than one milliampere in the test circuit should not be used for testing transistors. 4. The heat applied to a diode or transistor, when soldering is required, should be kept to a minimum by using low-wattage soldering irons and heat-sinks. ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 15 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 7. CONDUCTION OF ELECTRICITY however, lose all their resistance at temperatures near absolute zero, i.e. 0°K; this phenomenon is called Superconductivity. As we discussed earlier, protons lie in the atom's nucleus and are affectively fixed in position in solid material so that when charge moves 7.1 CONDUCTION OF ELECTRICITY IN SOLIDS in a solid, it is carried by its negatively charged electrons. Electrons are The only solids that conduct electricity freely at room temperature are easily liberated in some materials, metals, found on the left side of the periodic table, and graphite, which i.e. conductors, and all metals, particularly copper, gold and silver, are is one form of the carbon element. Nearly all of the other solids in the good examples of these. world, i.e., non-metal elements, solid ionic and covalent compounds, are non-conductors of electricity, i.e. are insulators. Materials in which the electrons are tightly bound to the atoms are called insulators, non-conductors, or dielectrics and good examples of these As metal atoms have few electrons in their outer shell, e.g. copper has include glass, rubber, and dry wood. only one (1), and these are not securely tied in orbit around its nucleus. This outer shell is the highest energy band of any atom occupied by However, there is a third kind of material where a solid has a relatively electrons and is called the Valence band. As the valence band is only small number of electrons that can be freed from their atoms in such a partially filled with electrons in a metal, there are numerous empty levels way as to leave a 'hole’ where each electron had been. The hole, and electrons move freely between atoms within the structure of the representing the absence of a negative electron, behaves as though it metal, though in a random way. However, under the influence of an were positively charged. An electric field cause the negative electrons electric field, usually created by a Potential Difference (PD) across it due to flow one way through the material and positive holes to move the to a battery or other power source, the flow is in one direction only as other way, so producing a current of electricity. Such a solid, called a the negative electrons are attracted to the positive side of the PD Semiconductor, generally has a higher resistance to the flow of current creating a current carried entirely by electron motion, in Figure 12 than a conductor such as copper, but a lower resistance than an insulator such as glass. If the negative electrons carry most of the current, the semiconductor is called N-type and if most of the current is carried by the positive holes, the semiconductor is said to be P-type. If a material were a perfect conductor, a charge would pass through it without resistance, while a perfect insulator would allow no charge to be forced through it. No substance of either type is known to exist at room temperature. The best conductors at room temperature offer a low, but not zero, resistance to the flow of current. The best insulators offer a high, but not infinite, resistance at room temperature. Most metals, Figure 12 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 16 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 7.2 CONDUCTION OF ELECTRICITY IN LIQUID Water Solutions that Conduct Electricity Conduction of Electricity in a Liquid The only liquid elements that As you know, water is an insulator so how do we explain the danger of conduct electricity are the liquid metals, e.g. at room temperature liquid bringing water and electricity into proximity with each other Pure or mercury is a conductor, and other metals will also continue to conduct distilled water will not conduct electricity, but everyday water we come electricity when melted. Pure covalent liquids, e.g. water, alcohol, across, e.g., from a tap, is not pure but contains contaminants, minerals, propane, hexane etc, are all non-conductors of electricity and even solid salts etc, and it is these substances that create ions that allow electricity covalent substances remain non-conductors when melted. to flow. Covalent bonding is the sharing of electrons between atoms. This type Any ionic solid dissolved in water will allow electricity to flow as the ionic of bonding occurs between two of the same element or elements close lattice breaks up and the ions become free to move around in solution. to each other in the periodic table. When molecules have the same A liquid that allows current flow is called an Electrolyte and all ionic affinity for electrons, covalent bonds are most likely to occur. Since both solutions and ionic melts are electrolytes. atoms have the same affinity for electrons and neither is willing to donate them, they share electrons in order to become more stable. Figure 13 Figure 13 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 17 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 7.3 CONDUCTION OF ELECTRICITY IN GASES In gases, electrical conductivity is very low and they act as an insulator or dielectric in their neutral state. However, if an electric field is applied to the gas in a confined environment, e.g. a tube, once it reaches a breakdown value, which will be different for each gas, it frees the valence electrons from the atoms in an avalanche process and forms a plasma. A plasma is an ionised gas and in chemical terms is considered to be a distinct phase of matter like solid, liquids and gases. Although gases in a plasma state do contain ions as the atoms lose electrons, due to their much lower mass, the electrons accelerate quicker than the heavier positive ions in response to an electric field and so carry the bulk of the current. Bring two conductors from a variable high-voltage source close to each other in air. When the potential difference reaches a certain value, we first perceive Figure 14 sputtering, then arcs occur between the two closest parts of the conductors. Due to an intense electric field some air molecules are ionised i.e. they have lost an electron and erects like a conductor with electrons and positive ions moving through molecules that have remained intact. If the field is sufficient there is a significant release of energy and generation of light. ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 18 of 19  3. ELECTRICAL FUNDAMENTAL BASIC AIRCRAFT MAINTENANCE TRAINING MANUAL 3.2. STATIC ELECTRICITY AND CONDUCTION 7.4 CONDUCTION OF ELECTRICITY IN VACUUM Vacuums under normal conditions are perfect insulators as they usually do not contain any charged particles. However, if a metal electrode is placed in a vacuum and is then heated, electrons are released through a process called Thermionic Emission. Thermionic emission is defined as the flow of electrons due to thermal vibration energy overcoming the electrostatic forces holding the electrons in place on the metal's surface. If a potential difference is then placed across the vacuum, current will flow as the electrons are attracted towards the positive potential. Figure 15 With this arrangement, the metal electrode creating the free electrons is called the Cathode, while the positive terminal is called the Anode. Figure 16 Figure 15 ISSUE 03, DATED 01 JUL 2024 FOR TRAINING PURPOSES ONLY Page 19 of 19