Recapitulation.
Theory. The above is the general theory every where accepted, and it has been very clearly stated by Mr. Ellis. A more extended statement with some interesting detail was given recently by that enthusiastic gad c&pable student of aeronautics, Major Baden Powell, of the English service, in the course of a lecture delivered before the Society of Fine Arts. From the lecture we take the following extracts. Ten or fifteen years ago authorities writing on the subject stated that if it were only possible to make engines so light as to weigh bu+ 10 lbs. per horse-power, there would be no difficulty in constructing a flying machine. A few years later, petrol engines were made of such a weight. To-day they are made, and on the rnarktt, weighing no more than 2J lbs. per horse-power Sceptics used to say that it would be impossible to raise a large apparatus off the ground by engines £nd propellers. To-day this has been accomplished, not once, but on many different occasions. They rlso urged that, once in the air, it would be impossible to balance the machine in steady flight. Now although this has proved somewhat of a stumbling block, we hear of men maintaining themselves for half an hour at a time in midair, while being propelled along at a great speed. Many have declared the landing would be a difficulty, but, without even considering these recent flights, we know that thousands of glides have been made with mancarrying gliding machines that have almost always ended satisfactorily. Chanute, summarizing the conclusions of many experimenters, has shown that the formula of Duchemin, P = 2P 1 sin a -r (1 -j3sin 2 a), is probably about correct, as the proportion between P, the pressure on an inclined surface, and P x that on the sui±ace, if placed perpendicular, a being the angle of inclination on the surface. Practice. The aeronouts who claim to have got the most out of the aeroplane e,s above referred to are the Brothers Wright, of Dayton, Ohio, U.S.A. Their claim is on record as follows. The aeroplane was motor-driven and weighed 925 lbs. :—
The Wrights have not appeared since, and Santos Dumont hf.s come to grief with an aeroplane designed to eclipse the feats of the famous " No. 14 bis." Here is the Times account :—: — " M. Santos Dumont on Nov. 15 made an attempt to win the Deutsch-Archdeacon Aerial Navigation Prize on the manoeuvring grounds at Issy-les-Moulineaux. There was not a breath of air to hinder the trial, when M. Santos Dumont had his apparatus taken to the starting point, and took a run of about 50 metres for the flight. The motor was started, but the aeroplane passed the two ftegs which marked the spot at which the flight wes to begin without rising from the ground. M. Santos Dumont stopped his engine and returned to the starting point. The second attempt was slightly more successful, for at the precise moment of passing between the flags the aeronaut brought the front plane into use and the machine at once rose easily to a height of nearly five metres. A false step on the part of the aeronaut, how-
ever, brought it back to earth, after covering about 50 metres. The airship fell to the ground somewhat heavily, but suffered no damage. M. Santos Dumont continued his attempts, but could not travel more than short distances." Question. Tbis failure, together with the reticence of the Brothers Wright and of their successors or representatives, made one doubt whether the aeroplane after all is the right kind of flier. These doubts were voiced as far back as August last by two officers in the Greek service, who strongly condemned the aeroplane as a proved failure, by reason of the unsolved difficulty of rising, and advocated the horizontal screw as the only effective power for lifting purposes. They thus represented the school — a rather numerous one — which has pinned its faith on the horizontal screw propeller as a means of overcoming the force of gravity. This was the principle advocated by Jules Verne in bis celebrated story of the '• Clipper of the Clouds." The objection by the opponents of this theory is that the lifting power of the sciews must be more or less destroyed when the propelling screws are brought into action : and there are besides doubts as to the efficiency of screw propellers for lifting purposes. With regard to the latter point M. Dufaux, of Paris, demonstrated in 1905 in one expeiiment on a small scale that the lifting power of a horizontal screw was about 17 lbs. per unit h.p* It is upon this question that light is thrown by the paper of the two Greek officers above alluded to — lieutenant Tsoucalas of the navy, and I^ieutenan Vlahavas of the artillery. The paper was read by the former at the meeting; iv July of the French Academic dcs Sciences, and published in the Comptes Rendus. In this paper, which supplies a comparative study of aeroplanes and blade d air propellers (hel ; copteres) the authors made a comparison between the two modes of attacking the problem relating to the movement of bodies heavier than air. The investigation is based absolutely upon mathematical analysis of the fact. After having calculated the most favourable inclination for the surfaces of the aeroplanes, they condemned the aeroplane since it presents no advantage in any way as compared with the screw. Indeed, in the most favourable position for the aeroplane, but one not practically possible, the screw will give with one third of the work needed for the aeroplane the same amount of sustentation. Finr.lly, the authors, makinguse in all cases of analysis, con lend that the theory relied upon hitherto by experimenters with aeroplanes must be rejected, since in effect it conducts to perpetual motion. They thus claim to demolish a theory which until now has been accepted e,s axiomatic, and having shown this to be so, there remains no advantago whatever in the use of the aeroplane. \ll future attempts should henceforth, therefore, they urge, be made with the screw or with other systems, based on direct action. The authors say the introduction of aeroplanes with their imagined advantages, has given a wrong direction to the efforts of experimenters who desired to attack the problem of the movements of bodies heavier than air, and these have been encouraged by the apparent success of certain recent but fallacious tests. In fact, they add, a careful analysis of these experiments leads to the conclusion that these results have not been in the nature of flight, but were due to a leap in the air. It remains to be seen whether M Farman's machine is to be included in the above general condemnation, but for all that, it has flown.
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Bibliographic details
Progress, Volume III, Issue 4, 1 February 1908, Page 129
Word Count
1,135Recapitulation. Progress, Volume III, Issue 4, 1 February 1908, Page 129
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