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Ailerons and Wing Warping

Fig. 17 shows the control surfaces or "Ailerons" (A-A’), mounted near the tips, and at the rear edge of the wing W. As shown, they are cut into and hinged to the main wings so that they are free to move up and down through a total angle of about 60 degrees. In a biplane they may be fitted to the upper wing alone or to both top and bottom wings, according to conditions. For simplicity we will consider only the monoplane in the present instance.

In Fig. 18, a front view of the monoplane, the machine is shown "heeled over" so that the wing tip (w) is low. To correct this displacement, the aileron (A) on the low side, is pulled down and the aileron (A') on the opposite end is pulled up. This, of course, increases the lift on the low end (w) and decreases the lift on the high side (w'). The righting forces exerted are shown by L-L’. The increased angles made by A-A’ with the wind stream affects the forces acting on the wings, although in opposite directions, causing a left hand rotation of the whole machine. In Fig. 19, conditions are normal with the machine on an even keel and with both ailerons brought back to a point where they are level with the surface of the wing, or in "neutral." Fig. 20 shows the machine canted in the opposite direction with (w') low and (w) high. This is corrected by bringing down aileron (A') and raising (A), the forces L-L' showing the rotation direction. By alternately raising and lowering the ailerons we can correspondingly raise or lower the wing tips. It should be noted here that in some machines the ailerons are only single acting, that is, the aileron on the low side can be pulled down to increase the lift, but the opposite aileron remains in the plane of the wings, and does not tend to "push down" the high side. Since all of the aileron resistance in a horizontal direction is now confined to the low side, it turns the machine from its path, the high wing swinging about the lower tip with the latter as a pivot. In the double acting control as shown in Figs. 17 to 23, the resistance is nearly equal at both tips and hence there is no tendency to disturb the flight direction. With single acting ailerons, the directional disturbance is corrected with the rudder so that when the aileron is pulled down it is necessary to set the rudder to oppose the turn. On early Wright machines the rudder and lateral controls were interconnected so that the rudder automatically responded to the action of the ailerons.