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Aviation History
1920
1920 - 1177.PDF
NOVEMBER II, 1920 A STUDY OF AEROPLANE RANGES AND USEFUL LOADS BY J. G. COFFIN Numerical Analysis THB essential data for the specific machine used in the calcula- tions are given in Table 1. The total wing and parasite resistances were computed for assumed total weights of 15,000, 13,000, 11,000, 9,000 and 7,000 lbs., respectively. Conditions for Maximum Range It is evident that the work required to fly a given distance, being the product of the total resistance, or required propeller thrust, by the distance, is least when the thrust is kept at its minimum values. The points of minimum drag were. TABLE I.—Summary Weight and wing loading 15,000 lbs. or 8 lbs. per square foot 13,000 lbs. or 6-92 lbs. per < square foot 11,000 lbs. or 5 • 86 lbs. per < square foot 9,000 lbs. or 4-80 lbs. ptr < square foot I 7 000 lbs orJ ^ ^* x^ v^ X &_JTU ft VJ* A 3 • 74 lbs. per •= square foot 1 Speed in m.p.h. 70-0 8o-o 90-0 IOO-O IIO-O oo-o 70-0 oo-o 90-0 IOO-O IIO-O 60-o 70-0 80-o 90-0 IOO-O IIO-O 50-0 60-o 70-0 8o-o 90-0 IOO-O IIO-O 42-7 500 60-o 70-0 8o-o 90-0 IOO-O IIO-O of total resistances for a machine with Monoplane K, x io4 19-2 149 II-6 9-40 7-88 22-6 16-6 I2-7 IO-O Q815 6-72I9-2 I4-I 10-75 8-48 6-90 5-70 22-6 15-7 "•5 8-82 6-97 5-66 4-68 24-0 17-6 12-3 9-02 6-85 5-44441 3-64 Biplane Ky= •85 mono. Ky X 10* 16-3 I2-5 9-9 8-o 6-6 19-2 14-1 io-8 8-55 6-91 5-71 16-3 120 9-15 7-23 5-86 484 192 *33 9'79 • 7 50 5-92 4-80 3-97 20-4 14-9 10-4 7-655-84 4-62 3-74 3 09 Monoplane Ky/K* 16-2 21 -2 21-7 196 168 93 198 21-8 20-5 17-3 15-0 16-2 21-5 21-3 18-2 15-2 13-0 9-2 2O-6 2 1-6 18-6 15-4 13-0 II-2 6-6 18-8 21-8 19-2 i5-i12-5 io-6 8-4 a variable load. Area of wing = 1,8 Biplane K,/K* = • 85 mono. K^/K, 138 18-0 18-4 16-7 H-3 7-9 16-8 i8-5 J7-4 14.7 12-7 13-8 18-3 18-1 15-512-9 II- 1 7-8 17-5 18-4 15-8 131 II- 1 9-5 5-6 16-0 i8-5 163 12-8 io-6 9-0 7-i Wing resistance = W/Bip. . (L D) lbs. 1,090 834 814 899 1,050 1.643 773 702 748 884 1,022 801 602 608 712 854996 1,152 515 491 570 686 815 946 1,250 439 -378 429 547660 111981 Parasite resistance X 1 10 lbs. 609 735 937 1,151 1,400 475 609 735 937 1,151 1,400 475 609 735 937 1,151 1,400 365 475 609 735 937 1,151 1,400 270 365 475 609 735 9371,151 1,400 75 squire feet. Total resistance wing + parasite lbs. 1,699 1,569 T,75i 2,050 2,450 2,118 1,382 J,437 1,686 2,035 2,422 1,276 1,211 1.343 1,649 2,006 2,396 1,517 990 I ICO 1,3051,623 1,966 2,346 1,520 804 853 1,038 1,082 1,597 1,928 2,381 Required horse- power 318 334 421 547719 339 258 306 404 543 710 204 226 286 39& 535 702 202 158 206 278 39O 524 689 173 107 136 194 274 383514 698 Z600 errrcr ori/AmAr/ON or WE/GHT offh« TotoJRes/sconce & Required Horsepoffhe 15000 L6. Bomber SeeTab/e /. therefore, located on the resistance curves. These points determined the most economical speeds and the corresponding required powers. The powers thus determined are seen not to be minimum powers. The minimum powers are but slightly less than those corresponding to minimum resistance, and occur at speeds slightly less than minimum resistance speeds. The minimum power is that for which the fuel consumption is least for a given time, andv as it turns out, is not the most economical power for flying the greatest distance. MX* 16000 ^ mo toco 1 MINIMUM' ftCSISTAMCC-TOTAL WEIGHTCUH\/C for 15000 Lb Bomber intobleZ / / / / ice as m mm IM *oo IUO ni» gm TotalAes/& n ~~ 00 Ve/ocr/y-, >-.•.."; •>;••-;-.», •...-..., Fig. 1 , . . The total resistance and required horse-power curves were then plotted against speed in the usual manner. See Table 1 and Fig. 1. * Part I of U.S. Advisory Committee for Aet >nautict Report No. 69. Fig- 2 "..._. The speed corresponding to minimum power is the speed at which a machine should fly in order to remain aloft the greatest possible time. In Fig. 2 the weight of the machine is plotted against minimum resistance. The curves in Figs. 1 and 2 show that— 1. The maximum range speeds decrease as the load 1179
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