3/3:1/99 AC 65-9A CHG 1 Sealing Compounds 169 Corrosion Control 171 Forms of Corrosion. 172 Factors Affecting Corrosion Preventive Maintenance Inspection 174 Corrosion-Prone Areas. 174 Corrosion Removal Corrosion of Ferrous Metals.
Corrosion of Aluminum and Aluminum Alloys.
Corrosion of Magnesium Alloys 179 Treatment of Titanium and Titanium Alloys.. 180 Protection of Dissimilar Metal Contacts 180 Corrosion Limits.. 180 Processes and Materials Used in Corrosion Control.
Chemical Treatments Protective Paint Finishes.
Aircraft Cleaning Interior Cleaning Powerplant Cleaning..
Solvent Cleaners.
Emulsion Cleaners Soaps and Detergent Cleaners.
Mechanical Cleaning Materials..
Chemical Cleaners Structural Metals.
Metalworking Processes. 193 Ferrous Aircraft Metals.. 194 Nonferrous Aircraft Metals. 198 Substitution of Aircraft Metals.
Principles of Heat Treatment.
Heat-Treating Equipment. 205 Heat Treatment of Ferrous Metals. 208 Casehardening.
Heat Treatment of Nonferrous Metals.
Solution Heat Treatment 213 Precipitation Heat Treating.. 214 Annealing of Aluminum Alloys.. 216 Heat Treatment of Aluminum Alloy Rivets.. 216 Heat Treatment of Magnesium Alloys.. 216 Heat Treatment of Titanium. 217 Hardness Testing ... 218 CHAPTER 7. PHYSICS General. 221 Matter. 221 Fluids 222 Temperature 225 Pressure.. 226 Kinetic Theory of Gases.. 227 Atmosphere 236 Bernoulli's Principle.. 242 Machines. 243 vii
Work, Power, and Energy. 249 Motion of Bodies 253 Heat.. 256 Sound 261 CHAPTER 8. BASIC ELECTRICITY General.. 267 Matter. 267 Static Electricity .. . 268 Electromotive Force . 271 Current Flow . 272 Resistance . 272 Basic Circuit Components and Symbols.. 274 Ohm's Law. 282 Series D.C. Circuits 286 Parallel D.C. Circuits. 290 Series-Parallel D.C. Circuits. 292 Voltage Dividers 294 Rheostats and Potentiometers 296 Magnetism. 298 Storage Batteries 306 Lead-Acid Batteries. 307 Nickel-Cadmium Batteries 313 Circuit Protective and Control Devices. 315 Switches 317 D.C. Measuring Instruments.. 320 Multimeters 325 Voltmeters 327 Ohmmeters. 329 Basic Circuit Analysis and Troubleshooting . 332 Alternating Current and Voltage. . 338 Inductance 344 Capacitance 346 Ohm's Law for A.C. Circuits 352 Transformers 358 Magnetic Amplifiers. 364 Vacuum Tubes 366 Transistors 369 Rectifiers 373 Filtering. 378 A.C. Measuring Instruments.. 380 Frequency Meters. 385 CHAPTER 9. AIRCRAFT GENERATORS AND MOTORS D.C. Generators . 387 Types of D.C. Generators . 394 Regulation of Generator Voltage.. 398 Differential Relay Switch . 402 Parallelling Generators _ 40 )З D.C. Generator Maintenance , 404 Voltage Regulator Operation . 407 Alternators .411 Brushless Alternator 414 Combined A.C. and D.C. Electrical Systems. 415 viii
Voltage Regulation of Alternators. 417 Alternator Constant-Speed Drive 423 Synchronizing Alternators. 430 Alternator Maintenance. 433 Inverters. 435 D.C. Motors. 438 Types of D.C. Motors 445 A.C. Motors. 451 Types of A.C. Motors. 452 459 ILS 461 461 461 462 463 463 464 469 474 477 477 479 481 485 486
LING, AN 489 General_ 489 489 491 492 495 495 Units _ 496 nits 496 497 497 Fire 500 dicate Extinguisher Suitab ility 503 503 505 507 stems 508 508 511 512 Con ditions. 512 Movement of Aircraft- 517 ix
Jacking Aircraft. 523 Cold Weather Suggestions- 525 CHAPTER 12. HANDTOOLS AND MEASURING DEVICES Introduction. 529 General-Purpose Tools_ 529 Metal Cutting Tools. 534 Layout and Measuring Tools. 542 Taps and Dies - 547
INTRODUCTION The use of mathematics is so woven into every area of everyday life that seldom if ever does one fully realize how very helpless we would be in the performance of most of our daily work without the knowledge of even the simplest form of mathematics. Many persons have difficulty with relatively simple computations involving only elementary mathematics. Performing mathematical computations with success requires an understanding of the correct procedures and continued practice in the use of mathematical manipulations.
A person entering the aviation field will be required to perform with accuracy. The aviation mechanic is often involved in tasks that require mathematical computations of some sort. Tolerances in aircraft and engine components are often critical, making it necessary to measure within a thousandth or ten-thousandth of an inch. Because of the close tolerances to which he must adhere, it is important that the aviation mechanic be able to make accurate measurements and mathematical calculations.
Mathematics may be thought of as a kit of tools, each mathematical operation being compared to the use of one of the tools in the solving of a problem. The basic operations of addition, subtraction, multiplication, and division are the tools available to aid us in solving a particular problem.
WHOLE NUMBERS Addition of Whole Numbers The process of finding the combined amount of two or more numbers is called addition. The answer is called the sum.
When adding several whole numbers, such as 4567, 832, 93122, and 65, place them under each other with their digits in columns so that the last, or right hand, digits are in the same column.
CHAPTER 1
MATHEMATICS When adding decimals such as 45.67, 8.32,
9.8122, and .65, place them under each other so that the decimal points are in a straight "up-anddown" line.
To check addition, either add the figures again in the same order, or add them in reverse order.
Subtraction of Whole Numbers Subtraction is the process of finding the difference between two numbers by taking the smaller from the larger of the two numbers. The number which is subtracted is called the subtrahend, the other number the minuend, and their difference is called the remainder. To find the remainder, write the subtrahend under the minuend, as in addition.
Beginning at the right, subtract each figure in the subtrahend from the figure above it and write the individual remainder below in the same column.
When the process is completed, the number below the subtrahend is the remainder.
To check subtraction, add the remainder and the subtrahend together. The sum of the two should equal the minuend.
Multiplication of Whole Numbers The process of finding the quantity obtained by repeating a given number a specified number of times is called multiplication. More simply stated, the process of multiplication is, in effect, a case of repeated addition in which all the numbers being added are identical. Thus, the sum of 6 + 6 + 6 + 6 = 24 can be expressed by multiplication as 6 X 4 = 24. The numbers 6 and 4 are known as the factors of the multiplication, and 24 as the product.
In multiplication, the product is formed by multiplying the factors. When one of the tactors single-digit integer (whole number), the product is formed by multiplying the single-digit integer with each digit of the other factor from right to left, carrying when necessary.
When both factors are multiple-digit integers, the product is formed by multiplying each digit in the multiplying factor with the other factor.
Exercise. care, when writing down the partial products formed, to make certain that the extreme right digit lines up under the multiplying digit.
It is then a matter of simple addition to find the finai product.
EXAMPLE Determine the cost of 18 spark plugs that cost $3.25 each.
3.25 X18 2600 325
58.50 When multiplying a series of numbers together, the final product will be the same regardless of the order in which the numbers are arranged.
EXAMPLE MULTIPLY: (7) (3) (5) (2) = 210 7 21 105 35 X3 X5 X2 or X5 X2 X6 21 105 210 35 6 210 Division of Whole Numbers The process of finding how many times one number is contained in a second number is called division. The first number is called the divisor, the second the dividend, and the result is the quotient.
Of the four basic operations with integers, division is the only one that involves trial and error in its solution. It is necessary to guess at the proper quotient digits, and though experience will tend to lessen the number of trials, everyone will guess incorrectly at some time or another.
Placing the decimal point correctly in the quotient quite often presents a problem. When dividing a decimal by a decimal, an important step is to first remove the decimal from the divisor.
This is accomplished by shifting the decimal point to the right the number of places needed to eliminate it. Next, move the decimal point to the right as many places in the dividend as was necessary to move it in the divisor, and then proceed as in ordinary division.
FRACTIONS A fraction is an indicated division that expresses one or more of the equal parts into which a unit is divided. For example, the fraction § indicates that the whole has been divided into 3 equal parts and that 2 of these parts are being used or considered. The number above the line is the numerator; and the number below the line is the denominator.
If the numerator of a fraction is equal to or larger than the denominator, the fraction is known as an improper fraction. In the fraction 4, if the indicated division is performed, the improper fraction is changed to a mixed number, which is a whole number and a fraction:
15 A complex fraction is one that contains one or more fractions or mixed numbers in either the numerator or denominator. The following fractions are examples:
A decimal fraction is obtained by dividing the numerator of a fraction by the denominator and showing the quotient as a decimal. The fraction 8 equals 5 ÷ 8 = .625.
A fraction does not change its value if both numerator and denominator are multiplied or divided by the same number.
·×3-12-1 The same fundamental operations performed with whole numbers can also be performed with fractions. These are addition, subtraction, multiplication, and division.
Addition and Subtraction of Common Fractions In order to add or subtract fractions, all the denominators must be alike. In working with fractions, as in whole numbers, the rule of likeness applies. That is, only like fractions may be added or subtracted.
When adding or subtracting fractions that have like denominators, it is only necessary to add or N
subtract the numerators and express the result What is the minimum droop to which the aileron as the numerator of a fraction whose denominator can be rigged?
is the common denominator. When the denomi- FIRST: Reduce the fractions to a common fractions to a common denominator before pro- nators are unlike, it is necessary to first reduce the denominator.
ceeding with the addition or subtraction process. ] = 4Ở 35 5 - ≤ 10 8
EXAMPLES NEXT: Subtract the numerators, and express
1. A certain switch installation requires g-inch the result as in the above examples.
plunger travel before switch actuation occurs. If š-inch travel is required after actuation, what will be the total plunger travel? 35 10 - 40 - 40 8 27 FIRST: Add the numerators.
5+1=6 NEXT: Express the result as the numerator of a fraction whose denominator is the common denominator.
8† 8
2. The total travel of a jackscrew is 18 of an inch. If the travel in one direction from the neutral position is 76 of an inch, what is the travel in the opposite direction?
FIRST: Subtract the numerators.
13 - 7 = 6 NEXT: Express the result as the numerator of a fraction whose denominator is the common denominator.
1б-}-
3. Find the outside diameter of a section of tubing that has a l-inch inside diameter and a combined wall thickness of & inch.
FIRST: Reduce the fractions to a common denominator.
2 5 5 8 8 NEXT: Add the numerators, and express the result as the numerator of a fraction whose denominator is the common denominator.
2 5
4. The tolerance for rigging the aileron droop of an airplane is ⅜ inch plus or minus ⅖ inch.
Finding the Least Common Denominator When the denominators of fractions to be added or subtracted are such that a common denominator cannot be determined readily, the LCD (least common denominator) can be found by the continued division method.
To find the LCD of a group of fractions, write the denominators in a horizontal row. Next, divide the denominators in this row by the smallest integer that will exactly divide two or more of the denominators. Bring down to a new row all the quotients and numbers that were not divisible.
Continue this process until there are no two numbers in the resulting row that are divisible by any integer other than one. Multiply together all the divisors and the remaining terms in the last row to obtain the least common denominator.
EXAMPLE What is the LCD for 3, 18, 36, 13?
FIRST: Write the denominators in a horizontal row and divide this row by the smallest integer that will exactly divide two or more of the numbers.
2 8 20 36 45 4 10 18 45 NEXT: Continue this process until there are no two numbers in the resulting row that are divisible by any integer other 2 8 20 36 45 2 10 18 45 2 9 45 3 2 5 15 5 5 1 3
THEN: Multiply together all the divisors and Also, the 18 and 3 are both exaetly divisible remaining terms in the last row to by 3.
obtain the LCD. 6 LCD = 2X2 X 3X3 X 5X2 = 360 18 Multiplication of Fractions 2 1 The product of two or more fractions is obtained The resulting 6 in the numerator and the 2 in ator of the product and by multiplying the denomi- by multiplying the numerators to form the numer- the denominator are both divisible by 2.
nators to form the denominator of the product.
The resulting fraction is then reduced to its lowest 1 terms. A common denominator need not be found 3×1 3 for this operation, as the new denominator in most 1×1 = 3 cases will be different from that of all the original 2 1
EXAMPLE What is the product of 3 X 22 X ½?
FIRST: Multiply the numerators together.
3 × 12 × 1 = 36 NEXT: Multiply the denominators together.
5 × 22 × 2 = 220 THEN: Reduce the resulting fraction to its lowest terms.
36 9 220 = 55 Cancellation Cancellation is a technique of dividing out or cancelling all common factors that exist between numerators and denominators. 'This aids in locating the ultimate product by eliminating much of the burdensome multiplication.
EXAMPLE What is the product of To X 3?
The product could be found by multiplying 18 X 5 and 10 × 3, then dividing the product of the numerators by the product of the denominators. However, a much easier method of solution is by cancellation. It is apparent that the 10 in the denominator and the 5 in the numerator can both be divided an exact number of times by 5.
18 Iø X = 2 The fraction is thus reduced to its lowest terms, and the final multiplication and division steps are performed with ease when compared with the task of multiplying and dividing the larger fractions.
Division of Common Fractions The division of common fractions is accomplished most conveniently by converting the problem into a multiplication of two common fractions.
To divide one fraction by another fraction, invert the divisor fraction and multiply the numerators together and the denominators together. This is known as the inverted divisor method.
Always keep in mind the order in which the fractions are written. It is important in division that the operations be performed in the order indicated. Also, remember that it is always the divisor that is inverted, never the dividend.
MIXED NUMBERS Mixed numbers can be added, subtracted, multiplied, or divided by changing them to improper fractions and proceeding as when performing the operations with other fractions.
EXAMPLE A piece of tubing 616 inches long is cut from a piece 24½ inches long. Allowing is inch for the cut, what is the length of the remaining piece?
FIRST: Reduce the fractional parts to like fractions and complete the subtraction process.
1 - 16 3 8 16-16-16 16 - I6 = 4
NEXT: Subtract the integer parts.
24 - 6 = 18 THEN: Combine the results obtained in each step.
18 + = 18- inches.
4 4
DECIMALS Decimals are fractions whose denominators are 10 or some multiple of 10, such as 100, 1,000, 10,000, etc. They are indicated by writing one or more digits to the right of a reference mark called a decimal point. Thus:
10 = 6, both read six tenths.
6 = .06, both read six hundredths.
100 1,000 = .006, both read six thousandths.
When writing a decimal, any number of zeros may be written at the right end without changing the value of the decimal. This may be illustrated in the following manner:
5 = 10 5 =≥50 = 100 = 500 = 1,000 = 2 A decimal fraction that is written where there is no whole number as .6, .06, etc., is called a pure decimal. When a whole number and a decimal fraction are written together as 3.6, 12.2, 131.12, etc., the number is known as a mixed decimal.
2.34 Ohms
37.5 Ohms .09 Ohms FIGURE 1-1. A series circuit.
Addition of Decimals When computing decimals, the rule of likeness requires that we add or subtract only like denominations. This rule was discussed previously under addition and subtraction of whole numbers.
To add or subtract decimal expressions, arrange the decimals so that the decimal points align vertically, and add or subtract as with integers.
Place the decimal point in the result directly below the decimal points in the addends or minuend and subtrahend.
EXAMPLES The total resistance of series circuit (figure 1-1) is equal to the sum of the individual resistances. What is the total resistance for the diagram shown in this example?
FIRST: Arrange the decimals in a vertical column so that the decimal points are in alinement.
2.34
37.5
- 115 NEXT: Complete the addition following the technique used in adding whole numbers. Place the decimal point in the result directly below the other decimal points.
2.31
37.5
- 09
39.93 ohms Subtraction of Decimals A series circuit containing two resistors has a total resistance of 37.27 ohms. One of the resistors has a value of 14.88 ohms. What is the value of the remaining resistor?
FIRST: Arrange the decimals in a vertical column so that the decimal points are in alinement.
37.27
- 14.88 NEXT: Perform the subtraction process using the procedure for subtracting whole numbers. Place the decimal point in the result directly below the other decimal points.
37.27 -14.88
22.39 ohms 5
Multiplication of Decimals The multiplication of a decimal by another decimal will always produce an answer smaller than either of the two numbers. When a decimal is multiplied by a whole number or by a mixed decimal, the answer will lie between the two When multiplying a decimal fraction by an integer or another decimal, establishing the position of the decimal point in the product causes the greatest amount of difficulty.
To multiply decimals, ignore the decimal points and multiply the terms as though they were whole numbers. To locate the decimal point in the product, begin at the right of the product and point off toward the left the number of decimal places that will equal the sum of the decimal places in the quantities multiplied.
EXAMPLE Using the formula, Watts = Amperes X Voltage, what is the wattage of an electric heater that uses 9.45 amperes from a 120-volt source?
FIRST: Arrange the terms and multiply. Ignore the decimal point.
9.45 ×120 000 1890 945 113400 NEXT: Locate the decimal point. Begin at the right of the product and point off toward the left the number of places that will equal the sum of the decimal places in the quantities multiplied.
In some problems the number of digits in the product will be less than the sum of the decimal places in the quantities multiplied. Where this occurs, merely add zeros to the left of the product until the number of digits equals the sum of the decimal places in the quantities multiplied.
EXAMPLE Multiply 218 by 203.
FIRST: Arrange the terms and multiply, ignoring the decimal point.
.218 .203 654 4360 44254 NEXT: Locate the decimal point. Add a zero to the left of the product so that the number of places will equal the sum of the decimal places in the quantities mult plied.
.218 X .203 654 4360 . 044254 Division of Decimals When one or both of the terms of a division problem involve decimal expressions, the quotient is found by converting the problem to one involving a whole number.
Two facts relating to division of decimals that must be borne in mind are: (1) When the dividend and divisor are multiplied by the same number, the quotient remains unchanged; and (2) if the divisor is a whole number, the decimal place in the quotient will align vertically with the decimal in the dividend when the problem is expressed in long division form.
To divide decimal expressions, count off to the right of the decimal point in the dividend the same number of places that are located to the right of the decimal point in the divisor. Insert a caret (A) to the right of the last digit counted.
If the number of decimal places in the dividend is less than the number of decimal places in the divisor, add zeros to the dividend, remembering that there must be at least as many decimal places in the dividend as in the divisor. Divide the terms, disregarding the decimal points entirely. Place the decimal point in the quotient so that it alines vertically with the caret mark in the dividend.
EXAMPLE The wing area of a certain airplane is 245 square feet; its span is 40.33 feet. What is the mean chord of its wings?
FIRST: Arrange the terms as in long division and move the decimal point to the right, adding zeros as necessary, and insert a caret.
10.33,/245.00.
NEXT: Divide the terms, disregarding the decimal points entirely. Add adaccuracy.
6 07
40.3311245.00.00 241 98 3 020 0 000 3 0200 2 8221 1979 THEN: Place the decimal point in the quotient so that it alines vertically with the caret mark in the dividend.
6.07 feet
40.33,21500,00 24198 3020 0000 30200 28221 1979 Rounding Off Decimals There is a general tendency to think of all numbers as being precise. Actually the whole realm of measurement involves numbers that are only approximations of precise numbers. For example, measurements of length, area, and volume are at best approximations. The degree of accuracy of these measurements depends on the refinement of the measuring instruments.
Occasionally it is necessary to round a number to some value that is practical to use. For example, a measurement is computed to be 29.4948 inches.
It is impractical, if not impossible, to measure this accurately with a steel rule which is accurate only to s1 of an inch.
To use this measurement, we can use the process of "rounding." A decimal expression is "rounded offi by retaining the digits for a certain number of places and discarding the rest. The retained number is an approximation of the computed or exact number. The degree of accuracy desired determines the number of digits to be retained.
When the digit immediately to the right of the last retained digit is a 5, or greater than 5, increase the last retained digit by 1. When the digit immediately to the right of the last retained digit is less than 5, leave the last retained digit unchanged.
EXAMPLE Round 29.4948 to the nearest tenth.
FIRST: Determine the number of digits to retain. In this case one-tenths being the first place to the right of the decimal point.
29.4948 NEXT: Change the value of the last retained digit, if required. In this case, since 9 is greater than 5, the final decimal is expressed thus:
29.4948 becomes 29.5 inches.
Converting Decimals to Common Fractions To change a decimal fraction to a common fraction, count the number of digits to the right of the decimal point. Express the number as the numerator of a fraction whose denominator is l followed by the number of zeros that will equal the number of digits to the right of the decimal
EXAMPLE Express .375 as a common fraction.
FIRST: Count the number of digits to the right of the decimal point.
375 NEXT: Express the number as the numerator of a fraction whose denominator is 1 followed by the number of zeros that will equal the number of digits to the right of the decimal point.
375 375 = 1000 7
Converting Common Fractions to Decimals To convert a common fraction, whether proper or improper, to a decimal, divide the numerator by the denominator. Add zeros to the right to permit carrying the quotient to the desired accu- 5 16 FIGURE 1-2. Locating the hole center.
Many times a dimension appearing in a maintenance manual or on a blueprint is expressed in decimal fractions. In order to use the dimension, it must be converted to some equivalent approximation applicable to the available measuring device. From the mechanic's standpoint, the steel rule will be the device most frequently used.
To change a decimal to the nearest equivalent fraction having a desired denominator, multiply the decimal by the desired denominator. The result will be the numerator of the desired fraction.
EXAMPLE When accurate holes of uniform diameter are required, they are first drilled an inch undersize and reamed to the desired diameter. What size drill would be used before reaming a hole to .763?
FIRST: Multiply the decimal by the desired denominator of 61.
3052 1578 48832 NEXT: Round the product to a whole number and express it as the numerator of the desired denominator.
18.332 - 19 THEN: To determine the drill size, subtract ay inch from the finished hole size.
19 48 61-71-61 = pinch dru.
EXAMPLE Find the distance the center of the hole (figure I-2) is from the plate edges when the center of the hole is in the center of the plate. Express the length and width of the plate in decimal forms, and then divide each by 2. Express the final result to the nearest 32nd.
FIRST: Change the mixed numbers to improper fractions.
16 - 16° 5 = 29 NEXT: Convert the improper fractions to decimal expressions.
87 29
- = 5.4375; = 3.625 16 8 THEN: Divide the decimal expressions by 2 to find the center of the plate.
5.4375 = 2.7188; 3.625
- = 1.813 2 2 FINALLY: Express the final results to the nearest 32nd.
32' 1.813 = 126 23
2.7188 = 2 32
PERCENTAGE There are many problems that arise every day involving the percent expression. The greatest number of percentage problems involve some kind of comparison of a part to the whole. Such comparisons become percentage problems when the ratio fraction is expressed as a percent.
A fraction having the specific power of 100 for the denominator is given the name percent. When writing these fractions, the percent symbol (%) is substituted for the denominator. Any common fraction or decimal can be expressed as a percent.
The fraction 4 can thus be expressed as .20 or as 20 percent or simply as 20%. Note that the percent is the same as the decimal fraction except that the decimal point has been moved two places to the right and deleted after "percent" or the symbol "%" has been added.