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Aviation History
1917
1917 - 0861.PDF
AUGUST 23, .1917. -.-... -- ••-.--- .-•->;";• -.. , f^>»*"*" | SIX UNITED STATES ARMY WING SECTIONS. By Captains EDGAR S. GORRELL and H. S. MARTIN, U.S.A.* IN these days it is a matter of some difficulty to obtain data relating to modern wing sections, as tests made by M. Eiffel and the N.P.L. are not to be made public until after the war. The following particulars of six new sections evolved in America should therefore be of considerable interest inasmuch as some of them appear to be a considerable improvement on sections of which particulars were published before the outbreak of war. That sections as good as or better than these have been produced in Europe during the last year or so may be taken for granted, but details of such sections are not, as has already been pointed out, available for publication. Owing to the uncertainties arising out of the U-boat campaign, the copy of our American contemporary Aviation, to whom we are indebted for this interesting contribution, did not reach us, and we have therefore had to wait until we were able to procure another copy, hence the delay in giving our readers the benefit of the information in this report.-—ED. THESE wing sections, developed by the Aviation Section ofthe Signal Corps, offer considerable interest both from an aerodynamical and a structural point of view. Developedpartly from the latter point, they have proved to* be efficient and show very satisfactory lift coefficients. Structural Development of the Sections. In Fig. 1 are shown the dimensioned outlines of the sixsections tested. Some of the considerations involved in developing the sections are interesting.The U.S.A. i is a modification of the Clark aerofoil (char- acteristics and dimensions of which are described in Hun-saker's " Dynamical Stability of Aeroplanes "). This was an excellent high speed wing with a maximum lift-drift of 18.By increasing the depth at the position of rear spar, it was made structurally much more practical, the maximum liftwas increased and the maximum lift-drift ratio only reduced very slightly.The U.S.A. 2 has the same upper surface as the R.A. F. 3, but the lower/surface has been modified and deepened froma structural point of view, without any loss from the aero- dynamical point of view. * By permission of Professor C. H. Peabody, Professor of Naval Architecture,in charge of Department of Aeronautical Engineering, Massachusetts Institute of Technology. Abstract by Alexander Klemin and T. H. Huff. The U.S.A. 3 and U.S.A. 4 are both modifications of theU.S.A. 2. In the first 9«Sfton, the nose of a 36-in. chord has been moved forward f-in., and the ordinates of the first fifthof the 30-in. chord spread out accordingly. In the U.S.A. 4, the nose of a 30-in. chord has been moved back f-in. and theordinates of the first fifth of the 30-in. chord crowded out accordingly.The U.S.A. 5 was skilfully developed from both structural and aerodynamic considerations with very satisfactory results. Results of Tests.The tests were conducted under the standard conditions. Results for K.y, ¥Lx, L/D and centre of pressure motion aregiven in Table I, and in the curves of Figs. 2, 3 and 4. The wind tunnel speed was 30 m.p.h. in every case, and the models18-in. span by 3-in. chord—the dimensions generally employed and useful on that score for purposes of comparison.The National Physical Laboratory results, as published in the British Reports, are based on LV (chord of wing infeet x velocity of relative wind in feet /second) values of 6.3. In Eiffel's large laboratory with greater wind speeds the valuesof LV range from 16 to 40. The Institute tests are conducted with an intermediate value of 11 for LV. It is, therefore, notpossible to make strictly accurate comparisons without further tests which are now in progress at the Institute. It is, however, Lof i-4° — 2° — T° 0° i° ' 2° 3° j: 6° 8° io° 12° 5 16° 18° 2O° . 000399 .000156 .000432 .000721 . 000936 .001146 U.S.A. 1. .0001515 .0000905 .0000700 .0000653 .0000670 .0000688 L/D C.P. —2 1 64 72 6.15 11.00 14.00 16.60 .001510 .0000860 17.50 .340 .001878 .002230 .002580 .002910 .0001158 .0001558 .0002055 .0002595 16.20 14.30 12.60 11.20 AERODYNAMIC LABORATORY TESTS. ...... TABLE i. U.S.A. 2. - Kj, K* L/D C.P. —.000228 .000147 —i-55 .000363 .000108 3.37 .733 .000625 .0000943 6.64 .522 .000862 .0000872 9.88 .445 .001075 .0000816 13.26 .388% • .001292 .0000848 15.22 .352 .001678 .0001027 I§-34 •3I7 .002090 .0001320 15.80 .292 .002432 .000175 13-88 .276 .003179 .000270 n-75 .255 .003165 . 003080 .002882 L of i Ky —4° —.0001231 — 2° -.OOO52OO — 1° .0007650 0° .0009750 1° .0011840 2° .OOI382O 5° 8° 10° 12° 15° 16° 18° 30° .OOI77OO .OOI980O .OO256OO .00299O0 .OO33IOO .0003710 .0005520 . 00138500 U.S.A. 4. Kx .0001640 .0001150 .0001078 .0001032 .0001002 .0000995 ,0001115 .0001340 .0001900 .0002555 .0003100 L/D -0.75 4-52 7.11 9-44 11.80 13.90 15.88 14.80 I3-5O II .70 10.67 .0036150 .0034700 .0031000 .0004430 .0005580 .0007640 8.15 6.22 4.06 .620 •53o •463 •415 .316 •303 .290 .283 .003165 .0003040 10.40 .274 8.50 .276 5.60 .310 3.40 .360 C.P. .670 •525 .461 .416 .388 •347 •33O .298 •273 .276 .0036000 .0003545 10.15 -276 .276 •303 •335 .003362 .000410 .003100 .000701 .002770 .000871 U.S^A. 5. Kv Kx .0001500 .0000948 .0000830 .0000741 .0000803 .0000863 .0000966 .0001092 .0001290 .0001830 .0002380 .0002890 .0003290 .0003545 .0003910 .0004210 .0006900 .0008200 8.20 .247 4.41 .228 3.18 .230 L of i " Angle of wing chord to wind,lbs./sq. it./m.p.h. L/D = Ratio of lift to chord. Model: Size, 18 ins. x 3 ins. (54of standard air : . 07608 lbs./cub. ft. y —.000326 .000346 .000636 .000910 .001145 .001355 .001565 .001740 .001950 ^002470 .002870 .003130 .003240 .003285 .003235 .003205 .003150 ,002790 Ky = Lift coefficient in lbs./sq. ft./m.p.drift. C.P. = Distance of C.P. from sq. ins.). Material, brass. Velocity 861 L/D —1.58 3-64 7-67 12.28 14.28 15-72 16.21 15.98 15.35 13.52 12.08 10.84 9.84 9.25 8.28 7.63 4-57 3.41 C.P. •753 .566 .498 •444 •415 •377 •348 •337 •315 .303 .300 .298 .288 .292 .298 •33o .368 K, .000506 .000420 .000692 .000928 .001123 .001310 .001508 .001704 .001919 .002520 .002905 .003160 •003235 .003240 .003215 •003155 .003125 .002889 K,, U.S.A. 3. K, .0001589 .0001052 .0000845 .0000835 .0000856 .0000889 .0000893 .0001073 .0001180 .0001823 .0002290 .0002830 .0003142 .0003410 .0003780 .0004460 .0006620 .0008570 U.S,A. 6. L/D -3-19 3-99 8.20 11.10 13.10M-75 16.16 15.88 16.18 13.82 12.70 11.15 10.30 9-5O 8.50 7.02 4-73 3-37 C.P. .676 .482 •403 •353 • 323 .295 .280 .260 .230 .220 .208 .204 .197 .197 .197 .236 .266 C.P.L/D .000276 .0001395 —1.98 .000272 .0000793 3.43 .910 .000567 .0000671 8.46 .600 .000845 .0000650 13.00 .498 .001057 .0000668 15.88 .458 .001255 .0000733 17.15 .439 .001455 .0000858 16.98 .402 .001662 .0000976 17.05 .388 .001846 .0001121 16.48 .365 .002415 .0001665 I4-5° -322 .002650 .0002160 12.-27* -3°6 .002861 .0002820 10.15 -3io .002910 .0003260 8.94 .310 .002980- .0004050 7-37 .002960 .0005300 5.58 .002900 .0006380 4.55 .002790 .0007900 3-53 .365 .002585 .0009000 2.88 .388 h. Kx = Drift coefficient inleading edge, in fractional part of of wind: 30 m.p.h. Density %328
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