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Aviation History
1928
1928 - 0847.PDF
SEPTEMBER 13, 1928 TOTAL PHES -10- T- l_ . . ._, COHPBESSIOM WITH | .; RIDtR AT-P° WIOTH OF GAP f-i">\ % Fig. 5. all birds having highly developed flying powers are provided with bastard wings, it would appear that the bastard wing and the remicle are not relics of obsolete members, but are performing some important function. The photographs of birds in flight, see Figs. 2, 3 and 4, show that the bastard wing is generally extended and separated from the main wing when a bird is starting, alighting or soaring. Fig. 2 shows a pigeon starting to fly. Fig. 3 a pigeon landing, and Fig. 4 the commencement of the down stroke. Figs. 6, 7 and 8. If the wings of a dead bird are stretched to the fullest extent by pulling the muscles, it will be found that the bastard wing is also projected beyond the front edge of the main wing, and also that its front edge is rotated downwards so that the bastard wing is at a negative angle to the main wing. The alula or the tip of the alula appears to be flexible in comparison with the adjacent portion of the main wing, and to be capable of being flexed upwards by the suction of the air over the leading edge of the wing. A number of experiments were made before the war with aeroplanes having small planes, or aviettes of various chords placed in front of, above, or under the leading edge of the main plane. See FLIGHT, November 20, 1914, pp. 1134 to 1136. The supplementary or rider planes were capable of being turned to any angle relative to the main plane, see Fig. 5, which also shows the variation of the lift on the main plane, set at an angle of 7°, caused by altering the inclination of the rider plane when in front of the leading edge of the main plane. The experiments proved :— (1) That small rider planes or alulas could be used for controlling aircraft. (2) That the maximum interference occurs with the rider plane near the front edge of the main plane and turned down at a negative angle to the main plane. (3) That the " burble " point of a main wing could be delayed and the lift increased by placing the rider plane in front of the leading edge of the main plane. Figs. 9 and 10. 783
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