MEASUREMENT SYSTEMS Our customary system of measurement (figure 1-23) is part of our cultural heritage from the days when the thirteen colonies were under British rule.
It started as a hodge-podge of Anglo-Saxon, Roman, and Norman-French weights and measures.
medieval times, commissions appointed by various English monarchs had reduced the chaos of measurement by setting specific standards for some of the most important units. Early records, for instance, indicate that an inch was defined as the length of "three barleycorns, round and dry" when laid together; a pennyweight, or one-twentieth of a Tower ounce, was equal to 32 wheatcorns from the "midst of the ear."
about 20 percent smaller than the Imperial gallon that the British adopted in 1824 and have since used to measure most liquids).
In short, as some of the founders of this country realized, the customary system was a makeshift based largely on folkways.
Metric System The metric system is the dominant language of measurement in use today. Most of the world countries used the metric system prior to World War II. Since the war, more countries have converted or are in the process of converting to the metric system. Only the United States and 13 smaller countries have not made the conversion.
Congress has the power to define the standard of weights and measures. Repeatedly the metric system has been proposed and each time the question has been voted down.
The metric system was developed by a French statesman, Talleyrand, Bishop of Autum, using a "meter" as a standard; the meter being a specific portion of the circumference of the earth at the From this base measurement the meter was developed and accepted as the standard. Divisions and multiples of the meter are based on the decimal system.
ELECTRIC
LENGTH MASS VOLUME TEMPERATURE CURRENT TIME METRIC Celsius Meter Kilogram Liter (Centigrade) Ampere Second
CUSTOMARY inch fluid ounce Fahrenheit ampere second foot teaspoon year tablespoon fathom cup rod pint mile quart gallon barrell peck bushel FIGURE 1-23. Some common units.
The Logic of Metric No other system of measurement that has been actually used can match the inherent simplicity of International Metric. It was designed deliberately to fill all the needs of scientists and engineers.
Laymen need only know and use a few simple parts of it. It is logically streamlined, whereas other systems developed more or less haphazardly.
At this time there are only six base units in the International Metric System. The unit of length is the meter. The unit of mass is the kilogram.
The unit of time is the second. The unit of electric the unit, whatever it may be. For example, kilo stands for 1,000: one kilometer equals 1,000 meters, and one kilogram equals 1,000 grams. Micro is the prefix for one millionth: one meter equals one million micrometers, and one gram equals one million micrograms (figure 1-24).
current is the ampere. The unit of temperature is the kelvin (which in common use is translated into giga (10°) One billion times the degree Celsius, formerly called degree centi- mega (10°) One million times grade). The unit of luminous intensity is the candela. kilo (103) One thousand times hecto (102) One hundred times All the other units of measurement in the Inter- deca (10) Ten times national Metric System are derived from these six base units. Area is measured in square meters; deci (10-') One tenth of speed in meters per second; density in kilograms per cubic meter. The newton, the unit of force, centi (10-3) One hundredth of is a simple relationship involving meters, kilograms, milli (10-3) One thousandth of and seconds; and the pascal, unit of pressure, is micro (10-*) One millionth of defined as one newton per square meter. In some other cases, the relationship between the derived nano (10-*) One billionth of and base units must be expressed by rather more pico (10- ) One trillionth of complicated formulas-which is inevitable in any measurement system, owing to the innate complexity of some of the things we measure. Similar relationships among mass, area, time and other quantities in the customary system usually require similar formulas, made all the more complicated because they can contain arbitrary constants. For example, one horsepower is defined as 550 footpounds per second.
The third intrinsic advantage is that metric is based on the decimal system. Multiples and subnultiples of any given unit are always related by powers of 10. For instance, there are 10 millimeters in one centimeter; 100 centimeters in one meter; and 1,000 meters in one kilometer. This greatly simplifies converting larger to smaller measurements. For example, in order to calculate the number of meters in 3.794 kilometers, multiply by 1,000 (move the decimal point three places to the right) and the answer is 3,794. For comparison, in order to find the number of inches in 3.794 FIGUrE 1-21. Names and symbols for metric prefixes.
Conversion: Metric To Conventional People tend to resist changes, usually because they do not understand cither the purpose of the change or the new order. Terminology for customary units and metric units have been discussed. A conversion table also has been included. Examples of its use follow:
To convert inches to millimeters, multiply the number of inches by 25. (Ex. 25 into mm =25 X25=625 mm) To convert millimeters to inches multiply millimeters by .01. (Ex. 625 mmX.04=25 inches.)
miles, it is necessary to multiply first by 5,280 and To convert square inches to square centimeters then by 12. multiply by 6.5. (Ex. 100 sq. in.X6.5=650 sq. cm.)
Moreover, multiples and submultiples of all the International Metric units follow a consistent nam- To convert square centimeters to square inches ing scheme, which consists of attaching a prefix to multiply by .16. (Ex. 100X.16=16 sq. in.)
IF YOU WHEN YOU KNOW: YOU CAN FIND: MULTIPLY BY:
LENGTH inches millimeters 25 feet centimeters 30 yards meters 0.9 miles kilometers 1.6 millimeters inches 0.04 centimeters inches 0.4 meters yards 1.1 kilometer miles 0.6 AREA square inches square centimeters 6.5 square feet square meters 0.09 square yards square meters 0.8 square miles square kilometers 2.6 acres square hectometers (hectares) 0.4 square centimeters square inches 0.16 square meters square yards 1.2 square kilometers square miles 0.4 square hectometers (hectares) acres 2.5 MASS ounces grams 28 pounds kilograms 0.45 short tons megagrams (metric tons) 0.9 grams ounces 0.035 kilograms pounds 2.2 megagrams (metric tons) short tons 1.1 LIQUID ounces milliliters 30 VOLUME pints liters 0.47 quarts liters 0.95 gallons liters 3.8 milliliters ounces 0.034 liters pints 2.1 liters quarts 1.06 liters gallons 0.26 TEMPER- degrees Fahrenheit degrees Celsius 5/9 ( after subtracting 32) ATURE degrees Celsius degrees Fahrenheit 9/5 (then add 32) FIGURE 1-25. Converting customary to metric.
Figure 1-26 is practically self explanatory. Meas- been converted to decimal divisions of inches and urements starting at 64 inch up to 20 inches have to millimeters.
Inches Inches Inches Inche Fractions Decimals MM Fractions Decimals MM Fractions Decimals M M F'ractions Decimals | M M 0004 .01 25/32 .781 19.844 2.165 55. 3-11/16 3.6875 93,663 004 7874 20. 2-3/16 2.1875 55.563 3.7008 54.
51/64 .797 20.241 2.2047 56. 3-23/32 3.719 94.456 1/64 0156 .397 3/16 8125 20.638 2-7/32 2:219 56.356 3.7401 95.
0197 .0295 -50 .75 53/64 .8268 828 21.034 21. 2-1/4 2.244 57. 57.150 3-3/4 3.750 3.7795 05.250 96.
1/32 03125 794 27/32 844 21.431 2-9/32 2.281 57.944 3-25/32 96.044 3/64 .0394 0469 55/64 859 8661 21.828 22. 2-5/16 2,2835 2012 58. 58.738 3-13/16 3.8125 3.8189 96.838 97.
.059 1.5 875 22,225 2.3228 59. 3-27/32 3.844 97,631 1/16 .062 1.588 8906 22.622 2-11/32 2.344 59.531 3.8583 5/64 .0781 .0787 1.981 2. 29/32 9055 9062 23. 23.019 2.3ł8 2.5622 60. 60.325 3-7/8 3.875 0.8976 08.425 3/32 094 2.381 59/64 .922 23.416 2.4016 61. 3-29/32 3.9062 99.219 7/64 .0984 2.778 15/16 .0449 9375 24. 23.813 2-13/32 2-7/16 2.406 2.438 61.119 61.913 3-15/16 5.9370 3.9375 100. 100.013
24.606 35005 24.209 2-15/165 2.4803 2.469 2,4409 53 5m 62. 1-1/16 3-31/32 4.000 3.969 3.9764 100.806 101. 101.600- 2-1/2 2.500 4.002 103.188
1.000 25.400 2.5197 64. 4-1/8 4.125 104.775
1.0236 -17 2.531 64.294 4.1338 105.
1.062 L.0312 26.988 194 2-9/16 2.559 2.562 65. 65.088 1-3/16 4-1/4 4.250 4.1875 106.363 107.950
27. 2-19/32 65,881 1-5/16 4.312 109.538
27.781 4.3507 110.
28. 2-5/8 66.675 1-3/8 4.375 111.125
28.575 1-7/16 4.438 112.713 2-21/32 655.450 1-1/2 4.500 114.300
1.156 29.369 1.5275 115.
2-11/16 4-9/16 1.562 115,888
1.1675 30.163 4-5/8 4.625 117.475 30,956 2-23/32 4-11/16 4.6875 119.063/
31. 2-3/4 1.7244 120.
31.750 70. 1-3/4 4.750 120.650
32. 2-25/32 70,6439 4-13/16 4.8125 122.238
32.544 71. 1-7/8 4.875 123.825
33. 33.338 2-13/16 71.4376 4-15/16 4.9212 125 125.413
34. 2-27/32 5.000 127.000 17326 2-7/8 5.1181 2-29/32 5.500
5.518 4173 2-15/16 2.0375 5.750 438 36.513 TS. 5.9055 2-31/32 2.969 6.000 469 37.306 2.9921 6.250 .4961 3.000 6.2092 S-1/32 2.0312 6.500
3.0315 77. 6.6929 I.5354 3-1/16 3.062 6.750
1.562 39.688 3.0709 78. 7.000
1.5748 3-5/32 3.094 7.0866
1.594 3.1102 79. 7.4803
1.6142 3.125 7.500
1.625 3.1496 80. T.8740
1.6535 3-5/32 3.156 8.000
1.6562 42.069 3-3/16 3.1875 8.2677
1.6875 42.863 3.1890 81. 8.500 5118 13. 1.6929 43. 3-7/32 3.219 8.6614 33/64 5156 13.097 1-23/32 1.719 43.656 3.2283 82. 9.000 35/64 17/35 531 .547 13.891 10.494 1-5/4 1.7323 1.750 44. 44.450 :3-1/4 3.2677 3.250 83. 0.0551 .5512 14. 1.25/32 1.7717 45. 3-9/32 3.281 9.500 9/16 14.288 1.781 45.244 3.3071 84. 9.8425
14.5 1.8110 3-5/16 3.312 10.000 37/64 .578 14.684 1-15/16 1.8125 46.038 3-11/32 3.344 10.2362 .5906 15. 1-27/32 1.844 46.831 3.3464 85.
19/32 15.081 1.8504 47. 3-3/8 3.375 85.725 11 11.000 39/64 10.910 1-7/8 1.875 47.625 3.3858 86. 11.0236 5/8 15,875 1.8898 48. 3-13/32 3.406 86.519 11.4173 41/64 16. 16.272 1-29/32 1.9062 1.929I 48.419 49. 3-7/16 3.4252 3.438 87. 87.313 † 12 12.000 21/32 .6496 .056 16.669 16.5 1-15/16 1.9685 1.9375 49.213 50. 3-13/32 3.469 3.4646 88. 85.106 1 1.3 13.000 13.7795 .6693 1-31/32 1.969 50.006 3-1/2 3.500 88.000 14 11.000 .672 17.066 2.000 50,800 3.5039 89.
11/16 .6875 17.463 2.0079 51. 3-17/32 3.531 89.694 15.7480 45/64 .703 17.859 2:1/32 2.03125 51.594 3.5433 90. 16 16.000 23/32 .7087 .719 18.256 2-1/16 2.0179 2.062 52. 52.388 3-9/16 3,562 3.5827 91. 90.4877 17 17.000 17.7165 .7283 18.5 2.0868 53. 3-19/32 3.594 91.281 18 18.000 47/64 .734 18.653 2-3/32 2.094 53.181 3.632 92. 19 .7480 19. 0-1/8 2.125 53.975 3-5/8 3.625 02.075 19.6350 49/64 3/4 .750 .7656 19.050 19.447 2-5/32 2.156 2.12€ 54. 51.769 3-21/32 3.656 5.6614 93. 92.869 20 20.000 FIcURE 1-26. Fractions, decimals, and millimeters.
...
FUNCTIONS OF NUMBERS The Functions of Numbers chart (figure 1-27) is included in this chapter for convenience in making computations. Familiarization with the various parts of this chart will illustrate the advantages of using "ready-made" computations.
Square Cube Circum- No. Square Cube Root Root ference Area 1 1.0000 1.0000 3.1416 0.7854 2 4 8 1.4142 1.2599 6.2832 3.1416 9 27 1.7321 1.4422 9.4248 7.0686 4 61 2.0000 1.5874 12.5664 12.5664 5 125 2.2361 1.7100 15.7080 19.635 216 2.4495 1.8171 18.850 28.274 7 49 343 2.6458 1.9129 21.991 38.485 64 512 2.8284 2.0000 25.133 50.266 9 81 729 00008 2.0801 28.274 63.617 10 100 1,000 3.1623 2.1544 31.416 78.540 11 121 1,331 2.2240 34.558 95.033 12 144 1,728 2.2894 37.699 113.10 13 169 2,197 3.6056 2.3513 40.841 132.73 14 196 2,744 3.7417 2.4101 43.982 153.94 15 225 3,375 3.8730 2.4662 47.124 176.71 16 256 4,096 4.0000 2.5198 50.265 201.06 17 289 4,913 4.1231 2.5713 53.407 226.98 18 324 5,832 4.2426 2.6207 56.549 254.47 19 361 6,859 4.3589 2.6684 59.690 283.53 20 400 8,000 4.4721 2.7144 62.832 314.16 21 441 9,261 97897 2.7589 65.973 346.36 22 484 10,648 4.6904 2.8020 69.115 380.13 23 529 12,167 1.7958 2.8439 72.257 415.48 24 576 13,824 4.8990 2.8845 75.398 452.39 25 625 15,625 5.0000 2.9240 78.540 490.87 26 676 17,576 5.0990 2.9625 81.681 530.93 27 729 19,683 5.1962 3.0000 84.823 572.56 28 784 21,952 5.2915 3.0366 87.965 615.75 29 841 24,389 5.3852 3.0723 91.106 660.52 30 900 27,000 5.4772 3.1072 94.248 706.86 31 1,961 29,791 5.5678 3.1414 97.389 754.77 32 1,024 32,768 6999 3.1748 100.53 804.25 33 1,089 35,937 5.7446 3.2075 103.67 855.30 31 1,156 39,304 3.2396 106.81 907.92 35 1,225 42,875 5.9161 3.2717 109.96 962.11 36 1,296 46,656 6.0000 3.3019 113.10 1,017.88 37 1,369 50,653 6.0828 3.3322 116.24 1,075.21 38 1,444 54,872 6.1644 3.3620 119.38 1,134.11 39 1,521 59,319 6.2450 3.3912 122.52 1,194.59 40 1,600 64,000 6.3246 3.4200 125.66 1,256.64 41 1,681 68,921 6.4031 3.4482 128.81 1,320.25 42 1,764 74,088 6.4807 3.4760 131.95 1,385.44 43 1,849 79,507 6.5574 3.5034 135.09 1,452.20 44 1,936 85,184 6.6332 3.5303 138.23 1,520.53 45 2,025 91,125 6.7082 3.5569 141.37 1,590.43 46 2,116 97,336 6.7823 3.5830 144.51 1,661.90 47 2,209 103,823 6.8557 3.6088 147.65 1,734.94 48 2,304 110,592 6.9282 3.6342 150.80 1,809.56 49 2,401 117,649 7.0000 3.6593 153.94 1,885.74 50 2,500 125,000 7.0711 3.6840 157.08 1,963.50 FIGURE 1-27. Functions of numbers.
Numbers through 100. The other columns contain compu- The number column contains the numbers 1 tations for each number.
Square Cube Circum- No. Square Cube Root Root ference Area 51 2,601 132,651 7.1414 3.7084 160.22 2,042.82 52 2,704 140,608 7.2111 3.7325 163.36 2,123.72 53 2,809 148,877 7.2801 3.7563 166.50 2,206.18 54 2,916 157,464 7.3485 3.7798 169.65 2,290.22 55 3,025 166,375 7.4162 3.8030 172.79 2,375.83 56 3,136 175,616 7.4833 3.8259 175.93 2,463.01 57 3,249 185,193 7.5498 3.8485 179.07 2,551.76 58 3,364 195,112 7.6158 3.8709 182.21 2,642.08 59 3,481 205,379 7.6811 3.8930 185.35 2,733.97 60 3,600 216,000 7.7460 3.9149 188.50 2,827.43 61 3,721 226,981 7018L 191.64 2,922,47 62 3,844 238,328 194.78 3,019.07 63 3,969 250,047 7.9373 3.9791 197.92 3,117.25 64 4,096 262,144 8.0000 4.0000 201.06 3,126.99 65 4,225 274,625 8.0623 4.0207 204.20 3,381.31 66 4,356 287,496 8.1240 4.0412 207.34 3,421.19 67 4,489 300,763 8.1854 210.49 68 4,624 314,432 8.2462 4.0817 213.63 3,631.68 69 4,761 328,509 8.3066 4.1016 216.77 3,739.28 70 4,900 343,000 8.3666 4.1213 219.91 3,848.45 71 5,041 357,911 8.4261 4.1408 233.05 3,959.19 72 5,184 373,248 8.4853 4.1602 226.19 4,071.50 73 5,329 389,017 8.5440 4.1793 229.34 4,185.39 74 5,476 405,224 8.6023 4.1983 232.48 4,300.84 75 5,625 421,875 8.6603 4.2172 235.62 4,417.86 76 5,776 438,976 8.7178 4.2358 238.76 4,536.46 77 5,929 456,533 8.7750 4.2543 241.90 4,656.63 78 6,084 474,552 8.8318 4.2727 245.05 4,778.36 79 6,214 493,039 8.8882 4.2908 248.19 4,901.67 80 6,400 512,000 8.9443 4.3089 251.33 5,026.55 81 6,561 531,441 9.0000 4.3267 254.47 5,153.00 82 6,724 551,368 9.0554 4.3445 257.61 5,281.02 83 6,889 571,787 9.1104 4.3621 260.75 5,410.61 84 7,056 592,704 9.1652 4.3795 263.89 5,541.77 85 7,225 614,125 9.2195 4.3968 267.04 5,674.50 86 7,396 636,056 9.2376 4.4140 270.18 5,808.80 7,569 638,503 9.3274 4.4310 273.32 5,941.68 88 7,741 681,472 9.3808 4.4480 276.46 6,082.12 89 7,921 704,969 9.4340 4.4647 279.60 6,221.14 90 8,100 729,000 9.4868 4.4814 282.74 6,361.73 91 8,281 753,571 9.5394 4.4979 285.88 6,503.88 92 8,461 778,688 9.5917 4.5144 289.03 6,647.61 93 8,649 804,357 9.6437 4.5307 292.17 6,792.91 94 8,836 830,584 9.6954 4.5468 295.31 6,939.78 95 9,025 857,375 9.7468 4.5629 298.45 7,088.22 96 9,216 884,736 9.7980 4.5789 301.59 7,283.23 97 9,409 912,673 9.8489 4.5947 304.73 7,389.81 98 9,604 941,192 9.8995 4.6104 307.88 7,542.96 99 9,801 970.299 9.9499 4.6261 311.02 7,697.69 100 10,000 1,000,000 10.0000 4.6416 314.16 7,853.98 FICURE 1-27. Functions of numbers (continued).
Square Square is the product obtained by multiplying a number by itself: 1X1=1, 2X2=4, 17X17=289.
Squaring may be considered a special form of area computation: Area=Length multiplied by Width, A-LXW.
Cube Cube is the product obtained by multiplying a number by itself, then multiplying that product by the number again: 1X1X1=1, 2X2X2=8, 13X13X13=2,197. Cubing may be considered specialized form of volumn computation:
Volume= Length multiplied by Width by Heighth, V=LXW×H.
Square Root Square root is the opposite of a "squared" number. The square root of a number is, that number which when multiplied by itself (squared) will produce the original or desired number: For example, the square root of 1 is 1, 1X1=1. The square root of 4 is 2. The square root of 24 is
4.8990. If an area of 24 square inches must be a perfect square, the length of each side would be
4.8990 inches.
Cube Root A cube root is the opposite of a "cubed" number.
The cube root of a number is that number which when multiplied by itself (cubed) will produce the original or desired number. The cube root of 1 is 1, 1X1X]=1. The cube root of 27 is 3, 3X3X3=27. If a container of 100 cubic inches and cubic in shape is desired, then the length of each side would be 4.6416.
Circumference of A Circle by their diameter.
circumference = 3.1416, Di- 12X3.1416=37.699.
Area of A Circle Area of a circle is the number of square units of measurement contained in the area circumscribed by a circle of the diameter of the listed number.
This is calculated by the formula (7) Xr'=a,
(7) multiplied by the radius squared equals area.
The radius is equal to one half the diameter. For example, diameter =2, radius =1. 3.1416X1=
3.1416 square units in a circle which has a diameter of 2. Another example, diameter =4, radius=
2. 3.1416X2°=3.1416X4=12.5664 square units.
lion micrograms.
33 ......
CHAPTER 2
AIRCRAFT DRAWINGS PRINTS The exchange of ideas is essential to everyone, regardless of his vocation or position. Usually, this exchange is carried on by the oral or written word; but under some conditions the use of these alone is impractical. Industry discovered that it could not depend entirely upon written or spoken words for the exchange of ideas because misunderstanding and misinterpretation arose frequently. A written description of an object can be changed in meaning just by misplacing a comma; the meaning of an oral description can be completely changed by the use of a wrong word. To avoid these possible errors, industry uses drawings to describe objects. For this reason, drawing is called the Draftsman's Lan- Drawing, as we use it, is a method of conveying ideas concerning the construction or assembly of objects. This is done with the help of lines, notes.
abbreviations, and symbols. It is very important that the aviation mechanic who is to make or assemble the object understand the meaning of the different lines, notes, abbreviations, and symbols that are used in a drawing. (See especially "The Meaning of Lines" section of this chapter.)
Prints are the link between the engineers who design an aircraft and the men who build, maintain, and repair it. A print may be a copy of a working drawing for an aircraft part or group of parts, or for a design of a system or group of systems. They are made by placing a tracing of the drawing over a sheet of chemically treated paper and exposing it to a strong light for a short period of time. When the exposed paper is developed, it turns blue where the light has penetrated the transparent tracing. The inked lines of the tracing, having blocked out the light, show as white lines on a blue background. Other types of sensitized paper have been developed;
prints may have a white background with colored lines or a colored background with white lines.
A print shows the various steps required in building anything from a simple component to a complete aircraft.
WORKING DRAWINGS Working drawings must give such information as size of the object and all of its parts, its shape and that of all of its parts, specifications as to the material to be used, how the material is to be finished, how the parts are to be assembled, and any other information essential to making and assembling the particular object.
Working drawings may be divided into three classes: (1) Detail drawings, (2) assembly drawings, and (3) installation drawings.
Detail Drawing A detail drawing is a description of a single part, given in such a manner as to describe by lines, notes, and symbols the specifications as to size, shape, material, and methods of manufacture that are to be used in making the part. Detail drawings are usually rather simple; and, when single parts are small, several detail drawings may be shown on the same sheet or print. (See detail drawing at the top of figure 2-1.)
Assembly Drawing An assembly drawing is a description of an object made up of two or more parts. Examine the assembly drawing in the center of figure 2-1.
It describes the object by giving, in a general way, the size and shape. Its primary purpose is to show the relationship of the various parts. An assembly drawing is usually more complex than a detail drawing, and is often accompanied by detail drawings of various parts.
Installation Drawing An installation drawing is one which includes 3/4~ NOTE: all necessary information for a part or an assembly
- ALL BEND RADII 3/16 of parts in the final position in the aircraft. It -RADIUS OF CUT OUT shows the dimensions necessary for the location
- IS 1/4 of specific parts with relation to the other parts
- L.H. IS SHOWN and reference dimensions that are helpful in later 4 3/8 -R.H. - / OPPOSITE work in the shop. (See installation drawing at the bottom of figure 2-1.)
DETAILS MATERIAL
- 024 24ST ALCLAD
CARE AND USE OF DRAWINGS Drawings are both expensive and valuable;
- 2-3/18 consequently, they should be handled carefully.
Open drawings slowly and carefully to prevent tearing the paper. When the drawing is open, smooth out the fold lines instead of bending them backward.
5/16 To protect drawings from damage, never spread them on the floor or lay them on a surface covered with tools or other objects that may make holes in the paper. Hands should be free of oil, grease, or other unclean matter than can soil or smudge 4 1/8 ASSEMBL 3 1/2 the print. Never make notes or marks on a print, as they may confuse other persons and lead to incorrect work. Only authorized persons are permitted to make notes or changes on prints, and they must 5/16 sign and date any changes they make.
SYM. When finished with a drawing, fold and return it to its proper place. Prints are folded originally B1219AD4 RIVETS I2 REQ in a proper size for filing, and care should be taken
- 2 PLATE .064 24ST ALCLAD | REQ. so that the original folds are always used.
36-31290 SIDE | REQ 36-31290 SIDE | REQ.
TITLE BLOCKS FORWARD Every print must have some means of identification. This is provided by a title block (see 9/16 figure 2-2). The title block consists of a drawing number and certain other data concerning the drawing and the object it represents. This infor- INSTALLATION mation is grouped in a prominent place on the print, usually in the lower right-hand corner.
Sometimes the title block is in the form of a strip extending almost the entire distance across the bottom of the sheet.
Although title blocks do not follow a standard form, insofar as layout is concerned, all of them = : will present essentially the following information:
28 TO FUS. RL. (REF)
1. A drawing number to identify the print for filing purposes and to prevent confusing it FIGURE 2-1. Working drawings. with any other print.
the title block. Above the title block will be found AERONAUTICAL CENTER FEDERAL AVIATION ADMIN. OKLAHOMA CITY, OKLA. a notation such as: 470204-1LH shown; 470204- 2RH opposite. Both parts carry the same number, N° 1ADF "T" ANTENNA but the part called for is distinguished by a dash LOCATION A DETAILS number. Some prints have odd numbers for left- SCALE: FULL SIZE hand parts and even numbers for right-hand parts.
APPROVED: SUBMITTED JOSEPH DOE B.B. BLACK DR.BY: HBF СК.BY: TDY DATE 4-8-68 DR. AC-A-735 FIGURE 2-2. Title block.
2. The name of the part or assembly.
3. The scale to which it is drawn.
4. The date.
5. The name of the firm.
6. The name of the draftsmen, the checker, and the person approving the drawing.
Drawing or Print Numbers All prints are identified by a number, which appears in a number block in the lower right-hand corner of the title block. It may also be shown in other places-such as near the top border line, in the upper right-hand corner, or on the reverse side of the print at both ends-so that the number will show when the print is folded or rolled. The purpose of the number is for quick identification of a print. If a print has more than one sheet and each sheet has the same number, this information is included in the number block, indicating the sheet number and the number of sheets in the series.
Universal Numbering System The universal numbering system provides a means of identifying standard drawing sizes. In the universal numbering system, each drawing number consists of six or seven digits. The first digit is always 1, 2, 4, or 5 (figure 2-3), and indicates the size of the drawing. The remaining digits identify the drawing. Many firms have modified this basic system to conform to their particular needs. Letters may be used instead of numbers. The letter or number depicting the standard drawing size may be prefixed to the number, separated from it by a dash. Other numbering systems provide a separate box preceding the drawing number for the drawing size identifier.
In other modification of this system the part number of the depicted assembly is assigned as the drawing number.
SIZE 2 4 5 LENGTH 17" 22" INDEFINITE (ROLL) WIDTH 8-1/2" 17" 17,22,25,50,34, and 36 inches FIGURE 2-3. Standard blueprint paper sizes.
Reference and Dash Numbers Reference numbers that appear in the title block refer a person to the numbers of other prints. When more than one detail is shown on a drawing, dash numbers are used. Both parts would have the same drawing number plus an individual number, such as 40267-1 and 40267-2.
In addition to appearing in the title block, dash numbers may appear on the face of the drawing near the parts they identify. Dash numbers are also used to identify right-hand and left-hand In aircraft, many parts on the left side are like the corresponding parts on the right side but in reverse. The left-hand part is always shown in the drawing. The right-hand part is called for in
BILL OF MATERIAL A list of the materials and parts necessary for the fabrication or assembly of a component or system is often included on the drawing. The list usually will be in ruled columns in which are listed the part number, name of the part, material from which the part is to be constructed, the quantity required, and the source of the part or material. A typical bill of material is shown in figure 2-4. On drawings that do not have a bill of material, the data may be indicated directly on the drawing.
On assembly drawings, each item is identified by a number in a circle or square. An arrow connecting the number with the item assists in locating it in the bill of material.
BILL OF MATERIAL ITEM PART NO. REQUIRED • SOURCE CONNECTOR UG-21D/U 2 STOCK FIGURE 2-4. A typical bill of material.
OTHER DATA Revision Block Revisions to a drawing are necessitated by changes in dimensions, design, or materials. The changes are usually listed in ruled columns either adjacent to the title block or at one corner of the All changes to approved drawings must be carefully noted on all existing prints of the When drawings contain such corrections, attention is directed to the changes by lettering or numbering them and listing those changes against the symbol in a revision block (figure 2-5). The revision block contains the identification symbol, the date, the nature of the revision. the authority for the change, and the name of the draftsman who made the change.
To distinguish the corrected drawing from its previous version, many firms are including, as part of the title block, a space for entering the appropriate symbol to designate that the drawing has been changed or revised.
2 CHANGED PART NO. 5 E.O. 1 2/3/70 B.K.
REVISED DIMENSIONS • J. L.M. 7/1/69 E.K.P.
NO. REVISION AUTH. DATE SIGN.
FIGURE 2-5. Revision block.
Notes Notes are added to drawings for various reasons. Some of these notes refer to methods of attachment or construction. Others give alternatives, so that the drawing can be used for different styles of the same object. Still others list modifications that are available.
Notes may be found alongside the item to which they refer. If the notes are lengthy, they may be placed elsewhere on the drawing and identified by letters or numbers. Notes are used only when the information cannot be conveyed in the conventional manner or when it is desirable to avoid crowding the drawing. Figure 2-1 illustrates one method of depicting notes.
When the note refers to a specific part, a light line with an arrowhead leads from the note to the part. If it applies to more than one part, the note is so worded that no mistake can be made as to the parts to which it pertains. When there are several notes, they are generally grouped together and numbered consecutively.
Zone Numbers Zone numbers on drawings are similar to the numbers and letters printed on the borders of a map. They are there to help locate a particular point. To find a point, mentally draw horizontal and vertical lines from the letters and numerals specified; the point where these lines would intersect is the area sought.
Use the same method to locate parts, sections, and views on large drawings, particularly assembly drawings. Parts numbered in the title block can be located on the drawing by finding the numbers in squares along the lower border.
Zone numbers read from right to left.
Station Numbers A numbering system is used on large assemblies for aircraft to locate stations such as fuselage frames. Fuselage Frame-Sta 185 indicates that the frame is 185 inches from the datum of the aircraft. The measurement is usually taken from the nose or zero station, but in some instances it may be taken from the fire wall or some other point chosen by the manufacturer.
The same station numbering system is used for wing and stabilizer frames. The measurement is taken from the center line or zero station of the aircraft.
Finish Marks Finish marks are used to indicate the surface that must be machine finished. Such finished surfaces have a better appearance and allow a closer fit with adjoining parts. During the finishing process the required limits and tolerances must be observed. Do not confuse machined finishes with those of paint, enamel, chromium plating, and similar coating.
0000 FIGURE 2-6. Pictorial drawing.
Tolerances When a given dimension on a print shows an allowable variation, the plus (+) figure indicates the maximum, and the minus (-) figure the minimum, allowable variation. The sum of the plus and minus allowance figures is called tolerance. For example, using .225 + .0025 - .0005, the plus and minus figures indicate the part will be acceptable if it is not more than .0025 larger than the .225 given dimension, or not more than .0005 smaller than the .225 dimension. Tolerance in this example is .0030 (.0025 max. plus. 005 min.).
If the plus and minus allowances are the same, you will find them presented as .224 + .0025. The tolerance would then be .0050. Allowance can be indicated in either fractional or decimal form.
When very accurate dimensions are necessary, decimal allowances are used. Fractional allowances are sufficient when close dimensions are not required. Standard tolerances of -.010 or -⅔2 may be given in the title block of many drawings.
to apply throughout the drawing.
METHODS OF ILLUSTRATING OBJECTS A number of methods are used to illustrate objects graphically. The most common are pictorial drawings, orthographic projections, and diagrams.
Pictorial Drawings A pictorial drawing, figure 2-6, is similar to a photograph. It shows an object as it appears to the eye, but it is not satisfactory for showing complex forms and shapes. Pictorial drawings are useful in showing the general appearance of an object and are used extensively with orthographic projection drawings. Pictorial drawings are used in maintenance, overhaul, and part numbers.
Orthographic Projection Drawings In order to show the exact size and shape of all the parts of complex objects, a number of views are necessary. This is the system used in orthographic projection.
In orthographic projection there are six possible views of an object, because all objects have six sides-front, top, bottom, rear, right side, and left side. Figure 2-7(a) shows an object placed in a transparent box, hinged at the edges. The projections on the sides of the box are the views as seen looking straight at the object through each side. If the outlines of the object are drawn on each surface and the box opened as shown in (b), then laid flat as shown in (c), the result is a sixview orthographic projection.
It is seldom necessary to show all six views to portray an object clearly; therefore, only those views necessary to illustrate the required characteristics of the object are drawn. One-view, twoview, and three-view drawings are the most common. Regardless of the number of views used, the arrangement is generally as shown in figure 2-7, with the front view being the principal one.
If the right-side view is shown, it will be to the right of the front view. If the left-side view is shown, it will be to the left of the front view.
The top and bottom views, if included, will be shown in their respective positions relative to the front view.
One-view drawings are commonly used for objects of uniform thickness, such as gaskets, shims, and plates. A dimensional note gives the thickness as shown in figure 2-8. One-view drawings are also commonly used for cylindrical, spherical, or square parts if all the necessary dimensions can be properly shown in one view.
When space is limited and two views must be shown, symmetrical objects are often represented by half views, as illustrated in figure 2-9.
Aircraft drawings seldom show more than two principal, or complete, views of an object. Instead, generally there will be one complete view and one or more detail views or sectional views.
Detail View A detail view shows only a part of the object but in greater detail and to a larger scale than the principal view. The part that is shown in detail elsewhere on the drawing is usually encircled by a heavy line on the principal view. Figure 2-10 is an example of the use of detail views. The 39