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Aviation History
1932
1932 - 0513.PDF
FLIGHT, MAY 27, 1932 permits of arranging the internal drag bracing in the orthodox manner, which would not have been possible had all ribs been of the operated type. To avoid complication with ailerons forming the trailing edge of the variable-camber wing, it is not intended to carry the variable camber right out to the wing tips, but to leave the outer few feet of wing of normal fixed con struction, so that ailerons of normal type, although of short span, can be fitted here. It would have been pos sible so to design the camber-operating mechanism that lateral control was achieved by the variation of camber, but it was thought that for a first wing this complication might better be avoided. Near the root of the wing will be seen, in the photo graph of the model of a " Breda " monoplane, a peculiar of the wing into a high-lift one, because of its poor lift/ drag ratio, will alter the gliding angle into a steeper one, and so give a certain degree of control over the gliding angle. In other words, the deep camber will at the same time act as an air brake and allow the machine to descend always with its fuselage approximately horizontal, unless, of course, the pilot uses his controls to make it do otherwise. Owing to the fact that the angle of incidence as well as the camber is increased, it may be expected that the land ing run following a steep glide will be short, not only because the flight path in a glide is steep, but also because with the wing at a large angle to the fuselage, as soon as the wheels have touched and the tail drops, the wing will be at a very large ground angle, will have passed its MODEL OF UGO ANTONI WING : A variable camber wing has been mounted on one side of a model of a Breda monoplane, leaving the standard wing on the other side for comparison. The extended trailing edge near the fuselage is a flexible stabiliser. (FLIGHT Photo.) up-curved extension of the trailing edge. This is another Antoni patent, and is intended to give fore and aft stability to the wing. Signor Antoni has made many models of gliders, and the degree of stability he has obtained in model wings devoid of tails other than these flexible stabi lisers is astounding. What one particularly notices is the total absence of phugoid oscillations when the model glider is first launched. The glider picks up its proper attitude instantaneously without that hunting up and down which is apt to characterise any small model when it is first launched by hand, and before it has steadied down to its glide. It is the flexibility of the stabiliser which is responsible for this. Of the sort of increase in speed range which the Antoni variable-camber wing will give, it is difficult to judge. Looking at the demonstration rib, one imagines that in its flat form it may have a maximum lift coefficient of approximately 0.5 in British " absolute " units. It also seems likely that with the wing curved to its maximum camber, the maximum lift coefficient may be increased to something like 0.8, or possibly even a little more. Wind- tunnel tests on wings of deeply cambered section have rarely been persuaded to give a greater maximum lift coefficient than that. If we assume that this is the maximum of the Antoni wing, and that the wing loading is 8 lb./sq. ft., the mini mum speed with the wing " flat " would be about 56 m.p.h. If the maximum lift coefficient can be increased to 0.8, the minimum speed at that wing loading would be reduced to something like 44 m.p.h., a reduction for this wing loading of 12 m.p.h. Reduction in landing speed, or in other words increase in speed range, is not, however, the only advantage to be expected from a variable-lift wing. The tendency in modern aircraft is towards greater aerodynamic refinement, and the high-efficiency aeroplane has a habit of " floating " when being brought down for a landing, and the change angle of maximum lift, and will not, therefore, cause the machine to rise again, but will help materially in bringing the machine to a standstill. So far we have considered the variable-camber wing mainly as a means of increasing the speed range (Signor Antoni estimates that a speed range of something of the order of 4:1 should be attainable) and its use for causing a steep glide, with corresponding short run after landing. There is, however, another direction in which this type of wing may be expected to be beneficial. As an aircraft reaches a greater and greater height, it should, theoretic ally, alter its lift coefficient to suit the new conditions. This the Ugo Antoni wing will readily do by changing its camber, and it may thus be expected that for machines designed to operate at considerable altitudes a percep tible improvement in the rate of climb can be achieved by suitable use of the camber gear. Similarly, it may be ex pected that the ceiling will be improved. In the case of multiengined aircraft, it is conceivable that the variable-lift wing will also have certain advan tages. If one of the engines stops, the aircraft will have to fly at a somewhat reduced speed, unless the remaining* engines are to be run at much increased power. The re- d'uced speed may not correspond to the best efficiency of the machine unless the wing camber, or in other words the lift coefficient, can be made to suit the lower speed. Thus the Ugo Antoni wing may be found to improve the cruising efficiency and thereby save fuel. The Antoni-Gloster experiment is designed to discover, full scale, how much there is in the variable-lift wing in which the variation in lift is obtained by varying the camber. It is impossible to forecast what the results will be. Wind-tunnel tests would be of little value in a case like this, where so many other features play a part, and full-scale trials seem to be the only satisfactory way of solving the problem. The tests will be watched with the greatest interest. 473
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