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Aviation History
1911
1911 - 0358.PDF
(A IGHT A'pRIL 22, igil. STEERING BY COMPASS. By R.A. IN his article, " Steering by Compass," some time ago, Mr. Graham Davies opens a most important subject, and I propose, in pursuing jit, to make a few remarks on his most interesting contribution. In contrasting the leeway of dirigibles and aeroplanes, he introduce? the question of resistance, by which I imagine he means side resistance to a wind tending to set a machine to leeward of the course steered. Is this correct ? I understand that as the whole body of air is moving, the body resistance of a flyer of any size or shape is immaterial, except in its effect on speed. To take an analogy, an ocean current of 20 knots a day would set a 20 knot liner, a 9 knot tramp, or a glass bottle, equally 20 miles in a certain direction in the 24 hours. However, this is not a great matter, but is interesting as a matter of principle. Of course, one realises that the shorter time the air vessel remains in a particular current, i.e., the greater speed it possesses, the less is it forced out of its course as referred to the earth. His suggested arrangement for measuring leeway is simple and excellent if his card compass can be relied on to work with the vibration inseparable from an aeroplane. In any case, a glass plate as described, with a "lubber line" across it, would enable a fairly good estimate of the leeway to be made if it were placed close to the spirit compass used for steering. I would suggest as an addition to the steering compass an adjustable arm such as those in use in night marching compasses. The aeronaut could then, after measuring his leeway as suggested, set this arm to the required position, and would only have to keep the compass needle under the arm to be on his course. If arm and compass needle were marked with luminous paint, this arrangement would be as efficient by night as by day. The arm could easily be set by a pedal. Now I venture to think that the difficulties of aerial navigation have been exaggerated, probably because comparatively very few men have yet taken the same machine across country often enough to get accustomed to its peculiarities and behaviour in different winds. I do not think that a man who is accustomed to make passages in yachts or small sailing vessels by " dead reckoning," would take very long to find his way in the air after a short training. It is a delicate matter for one who has never made an ascent to expatiate on, but I will take the plunge, and set out my ideas for criticism. What an aviator wants to know in order to go from one place to another in a given time, is the course and the pace he must make through the air in order to make a different course and a different pace (i.e., that required to reach his destination up to time) over the earth. As Mr. Graham Davies shows, he can now, without any great difficulty, get his course and pace over the ground, lie can then take a "departure," as they say at sea, with the certainty that, unless the wind changes, he will reach his point at a certain time without taking any more observations at all. He knows his speed through the air by his whistle indicator, or other simple means, he has measured his speed over the ground by the Joanneton speed recorder, or the more (Retired), simple method of timing himself between two conspicuous points on the earth, and he knows that the difference of the two is the effect of the wind on his machine when kept on that particular compass bearing. The wind, of course, will soon change both in force and direction, and he will find it necessary to alter his course through the air in order to preserve the same course over the ground. His speed through the air remains constant, so he realises that any difference noticed in speed over the ground is due to this altered movement of the medium through which he is moving. With map and compass in front of him, he will soon get into the habit of noticing every change in the wind, and applying the necessary correction to his course, even though he is so high that he can only recognise towns by their relative size. As his education goes on he will observe that different changes of wind are accom panied by their special phenomena, dampness, squalls, and the like, and he will get more and more independent of his observations of earth. Moreover, I presume that a change of wind of any sudden ness would be recognised by a necessary re-adjustment of his balancing planes. This would give a clue to its direction and force. There is still a very big step forward to be taken before our pilot can conduct his vessel to a distant destination when he cannot see the earth at all, but it must be remembered that this would be equivalent to crossing the Atlantic entirely by " dead reckoning," a thing that could never be done with exactitude. If he can navigate a cloudy or misty sky with approximate accuracy so that he gets an observation of the earth, the course correction is comparatively a small one, it is surely all that can be expected. It is suggested that a lead plummet on a length of piano wire might be tried to get an idea of the vessel's leeway in a case like this. It would, of course, hang slightly to windward of the fore and aft line of the air vessel from which it was hung, and by its degree of divergence from that line would give an indication of the force and direction of the wind. One need hardly say it would have to be kept clear of the propeller. Besides this possibility, and the recognition of gusts from a certain direction by the necessary re-adjustment of balance, there is work already begun in the big field of meteorological research which will help the aerial navigator. When the prevailing currents at the different heights are mapped out, and a system of reports of con ditions existing from time to time sent by wireless telegraphy from balloons, captive or dirigible, is established, aerial navigation will have few uncertainties to contend with in the opinion of the writer. He ventures to forecast that in a very few years these considerations which we discuss with so much gravity to-day will be considered mere child's play. [It will be noticed that the expression "leeway "has been used to describe what "drift " would describe more exactly. The reason is that " drift," in its special artillery sense, is used to describe the deviation of a projectile from the plane of departure due to the spin given it by the rifling, and it struck the writer as just possible that the motion of an aeroplane's propeller, whether "clockwise" or counter " clockwise," might have a similar effect which might be very properly described as " drift."] THE EUROPEAN CIRCUIT. THE full rules for the European Aviation Circuit which is being organised by the Standard of London and Le Journal of Paris have now been issued. Up to the present over ^17,000 has been offered in prizes, as per the following list:— The Standard ... ^2,500 Le fournal ... ... ... ... ... 200,000 frs. The Town of Vincennes ... ... ... 25,000 ,, Le Petit Bleu 25,000, The Municipality of Liege 40,000 ,, The Town of Calais ... ... i5>ooo „ The Municipality of Brussels ... ... 10,000 ,, The Town of Spa ... ... ... ... 10,000 ,, The Netherlands Aviation Committee ... 40,000 ,, The competition will start from Paris on June 18th and traverse France, Belgium, Holland and England via Brussels, Utrecht, London and back to Paris. Between each of these four points there will be various landing places where the aviators will be obliged to come down in order to be checked, &c. Prizes will be offered for each section of the course as well as for the complete course. The prize money offered for the various sections will be divided among the first twelve aviators, the one securing first place taking 40 per A Four-seated Deperdussin. ONE of the latest monoplanes turned out at the Deperdussin Works has been designed to carry four passengers. It is fitted cent, and the others in certain other proportions down to the eleventh and twelfth who will receive 2 per cent. each. The competition is open to all aviators qualified at the date of the contest by the F.A.I, and using motor driven heavier-than- air machines. Aviators can only compete on a type of machine on which by June 15th next they shall have passed the necessary test to obtain an aviator's certificate. The same pilot must pilot the machine throughout the whole of the course but the machine may be changed, although any substituted machine must be of the same type as that which it replaces. Passengers may be carried, but they may not be changed during the day, and they must not be certificated aviators. Entries, accompanied by a fee of 100 francs, will be received up to May 30th, and double fees up to June 8th. All entrants have the right to withdraw up to June 8th, and if they do so half the entry fee will be returned, the same applying also to all those who actually start. Time alone will be the basis of the classification, the prizes for the different sections being awarded according to the time the machines have taken to cover that section, while the classification will be for the full course, according to the total times added together for the various sections. Copies of complete rules can be obtained from the Royal Aero Club. ®. ® with a 70-h.p. Gnome engine, and at Rheims on the 14th inst. Aubrun was flying on it with a single passenger for 45 mins., while in the evening he flew over to Mourmelon and back. 360
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