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Aviation History
1911
1911 - 0448.PDF
j/jJGHT) be its edgewise speed, v, the speed of fall, then its true speed, v, equals */ vi1 -f Vj*, and the angle, a, between v and the plane, is determined by the equation tan a = vy/v,. Substituting this value r / JI L vy IV il + sin "a) ,. . , ot a in equation (tf), we have — =—r—7-*-; . •• ..which, for fx 2 it Av-(i - sin-a) *,' Y. A 1 1 , T , ^ 0 + W'a«). high speeds and moderate loading, becomes vy - ^ ~ since a is small, and #„ is nearly equal to v. Under these conditions the speed of fall varies inversely as the speed of flight, which means that the rate of descent and the power expended may be made indefinitely small by sufficiently increasing the speed. Of course, if the air has an upward trend equal to or greater than vy the plane will soar continuously on a horizontal or ascending course. Suppose the gliding plane to dip o degrees below the horizon, and to have a forward resistance. The angle of impact of the air is 8-5 o, in which tan § = z\jvx, as before ; and, when steady motion is established, the horizontal component of air pressure, MAY 20, 1911 2 k% Ai? sin*sin*, . equalg the horizontai resistance. Accor- 1 -f- sin" S dingly the plane will glide continuously with the constant com ponent velocities, vx forward and v7 downward. If, however, the air has an upward trend equal to vy, or greater, the plane will glide continuously on a horizontal, or' ascending course. This is the principle of one kind of soaring practised by the birds.* It can be proved, by a slight extension of this argument, that soaring is possible even in a wind that alternately rises and falls. • The Wright Brothers report that they can glide continuously down a seven- degree slope at a speed of 18 miles an hour in still air. This means that if the air has an upward trend of 18 x sin f = zj miles an hour, they can glide on a horizontal course indefinitely at a speed of iZcosf= 17-06 miles an hour. Hence in a soaring pavilion having a forced upward draught of, say, 3 miles an hour, a group of machines could glide all day without motive power, rising and falling at pleasure. The power of such a draught is about j^th of a foot-lb. per second over each square foot of floor surface. Hence two horse-power can maintain such a draught continuously over 5,500 square feet of surface, working at an efficiency of 50 per cent. (To be concluded.) CORRESPONDENCE,. The name and address of the writer (not necessarily for publication) MUST in or containing queries. cases accompany letters intended foi insertion, Correspondents communicating' with regard to letters which they have read in FLIGHT, would much facilitate ready reference by quoting the number of each such letter. NOTE.—Owing to the %rcat mass of valuable and interesting corre spondence which we receive, immediate publication is impossible, but each letter will appear practically in sequence and at the earliest possible moment. The Sirie Monoplane. [1175] Aeroplanes are usually classed according to their distinctive features, as the Kleriot. Farnian and the Tellier, and the present one is no exception to the rule, except in this particular, that it takes its name not from its inventor but from the name of a tropical tree, which it resembles. The leaves of this tree are, in fact, miniature monoplanes, and soar through the air for long distances before they reach -the ground. The machine consists essentially of two large concave wings, somewhat similar in clinure to the wings of a crow when soaring. These wings are fixed to the main carriage, as indicated, and have a span of IS ft. from tip to tip. In Crossing one another they form a triangle, where the engine is fixed. The vertical plane between the wings is a control plane to prevent zig-zag Sight This takes the place of the •usual tail in other monoplanes. Two elevating planes are fixed at the front of the machine, and are operated from the carriage by means of rods. They can move in four different ways, so that by simply turning the right hand plane the machine swerves to the right. Planing up and down is accomplished in the same simple manner. The engine and petrol supply is conveniently placed to the operator. Numerous experiments have been carried out by the inventor on a model of this machine, and the results have been so highly satisfactory that he is led to believe that this type of monoplane will surpass in speed and stability many of the popular types of the present day* 2, Hamilton Terrace, East Partick. M. LESLIE-MILLER, Steering by Compass. [1176] May I be allowed to acknowledge the kindly references of C. O. and Mr. Graham Davies to my article on above subject. Both letters are interesting contributions to the discussion. I may point out that in'line 25 of the second column, " when " was omitted. It should read " so that when he gets an observa tion, &c. R.A. (retired). The Valkyrie Machines and the Hendon Demonstration. [1177] Having regard to various mis-statements which have appeared concerning the reasons for our Valkyrie military mono planes not taking part in the flying demonstration at Hendon last Friday, we shall be much obliged if you will publish this letter, in which we beg to give the facts of the case. Several days before the demonstration we were notified in writing that we must not fly on Friday except by invitation, and at the same time we were informed that it was not possible to extend any invita tion to us. No reason was forthcoming, although we protested most strongly. We may say that we were the first tenants of the Hendon Aerodrome. When Friday arrived we prepared to ascend at a time when no other machines were in the air, but were prevented from doing so, though our machine could easily have kept several thousand feet above the heights attained that day. We may add that our machines are all-British, and are able to execute certain evolutions important from a military point of view, and quite unattained by any other types of aeroplanes. On the days following the demonstrations they made numerous lengthy flights, attaining heights of over 2,000 feet, and showing their inherent stability by making complete circuits with both hands of the pilot off the controls and above his head, and this even rivals must admit marks a sensational advance in the factor of stability and safety. AH we ask is a fair field and no favour, and we think that surely even in England itself British enterprise should command that. T. W. MITCHELL, Manager, the Aeronautical Syndicate, Ltd. London Aerodrome, W. Hendon. Is the Helicopter Possible. [1178]. With reference to the above, and letter 1163 in your issue of May 6th, I do not wish to turn what has been, to me, an instructive correspondence into an argument, especially as I am able
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