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Aviation History
1922
1922 - 0070.PDF
/JL|CHT -FEBRUARY 2, 1922 AERODYNAMICAL REPORT AND TESTS ON THE EGGLESTON AIR-CELL GIANT BIPLANE* THIS test was carried out on.October 12 and 13, 1921, in the Curtiss 7-ft. wind tunnel, and was conducted by the Cox- Klemin Aircraft Corp., College Point, Long Island, N.Y., Consulting and Designing Engineers. The test followed standard methods, and was carried out on a model of scale 1 to 72 (1 in. = 6 ft.) at a wind speed of 30 m.p.h. The stabiliser was set at 30 to the wing chord. The tests included : (1) Lift, drift and pitching moment, with the Eggleston Air Cells in position ; (2) Lift and drift, with the Eggleston Air Cells replaced by standard type streamline struts. Stability.—In the vector diagram (Fig. 1) the results of the pitching moment tests are shown. This vector diagram indicates that, with the stabiliser at 30 to the wing chord, a very large degree of stability is secured. The vectors are well separated. Balance at cruising speed is secured if the load is arranged to bring the centre of gravity three-tenths of the chord length aft of the leading edge. The position of the vectors is such that, if the aeroplane tends to dive down, the aerodynamical forces will return it to its normal flight attitude. If the aeroplane tends to stall or go up by VECTOR DIAGRAM SCALE I IN-6 FT Fig. 1. Vector diagram for the Eggleston Air-Cell biplane test. the nose, the aerodynamical forces will return it to its normal flight attitude. The longitudinal stability of the plane may be, therefore, regarded as perfectly satisfactory. Results of Test for Lift and Drag.—The results of the test for lift and drag, with and without the Air Cells, are plotted in Fig. 2. These indicate that by replacing struts of standard form disposed in the manner of a Warren truss by the Eggles ton Air Cell : 1. The maximum lift is increased from 6-25 to 7*07 lbs. on the model, or approximately 13 per cent. * Aerial Age, U.S.A. 2. The maximum Lift/Drag ratio of the plane, which is a very fair measure of efficiency, is increased from 6-66 to 6-86, and the Lift/Drag at almost all angles is increased. 3. The general efficiency of the plane is high, particularly for a plane having two engine nacelles on either side, and short spans, with a larger number of interplane supports. Landing Speed.—(a) With Eggleston Air CelLs (eight in number), lhe maximum lift force on the model with the UFT *MO LI"/OHA& RATIO MODtL SCALE toi=(jfr WTTIICCLLJ LBS ON WNb SPEED 30K.PH VffTNOirruiiS-* K. * LlFT/DWa -*• fr 5 * F*» Lfi, 2. 1 1 V / ¥ r -A L.fT/, II It II 1 /' // // v ft II 1 r rf 0 KAO // II It ft / 1 1 ' I 1 ' 1 1 // // // // // / ^ / s / / / f // // t t A\ 8 "^v^ Y / / /r UFT ia ** , fry Z. ANGLE OF INCIDENCE -DEGREES • lb M ^ 0^" l , ~ ! Fig. 2. Lift and Lift/Drag curves for the Eggleston Air-Cell Biplane. Eggleston Air Cells in position is 7-07 lbs. speed is, therefore, given by the formula :— V2 The landing m 7.07 = 113,000 This is not 30 / allowing 113,000 52-7 m.p.h. 7.07 for scale effect. With scale effect and skilful piloting, it may be expected that the ship should land not much over 45 m.p.h. (6) Without Eggleston Air Cells.—The maximum Uft on ^_. ^—^ <^^ n^* mp m? wtf wf w W^ * ™ * •• AAA THE EGGLESTON AIR-CELL BIPLANE Three-quarter rear and front views of the scale model. 70
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