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Aviation History
1916
1916 - 0865.PDF
We have therefore: (%£»)'--•* At the same time the variation of the angle of attack 5a, through which the machine has passed ai the end of the time 8,' hsu diminished. It has become at the end of this time : dO] — So. - 8/, for the inclination of the machine to the horizontal has remained the same. For this variation of the angle of attack the value ot the central couple has become g r/'V„,4.s«,\'-' rfa, dv ,, V„,-n„,\a n A V.. '-5a, Si = 8 f cn> 8/ 8; This surface I* titled m such a way thtt during the longitudinal oscillation* of the machine it always retains an tavariaWe incidence wi h regard to tbe relative wind. It i» for thi* purpose fumuhed with a little tail 9 9, which with St constitutes a rigid simcturc. The displacement* of this tail arc magnified, and transmitted to the rear surface by a suitable mechanism In this manner the machine travels in calm air with reduced surface at the angle of normal flight. It resists duturUances by automatically increasing its rear surface. formula (8) shows that an aeroplane of which the incidence of the forward plane to the relative wind lema'ns invariable possesses by virtue of this fact a central couple that it generally large. (A simple calculation would prove that it is practically a mattmum for S, S.. when the tail is liitii. We sec, further, that if the rear surface can also be doubled for a So that the variation of the speed acquired under the influence ot the disturbance might be neglected it was necessary for 8> to be practically nil; it was consequently necessary to increase the angle «i to the minimum of the curve C| or to decrease m «, that it to say, H/W, W being the weight of the machine, and II the pull of the propeller. We would thus come to the question of means, whether an automatic regulation of toe conditions of carburation of the engine or an automatic adjustment of the weights J which does not at all amount to saying, in spite of the erroneous theories of some writers, that to decrease m ft it suffices once and for all to increase W. The aeroplane cannot be rendered stable by its design alone. It can only become so by an automatic alteration ot this design during a disturbance. However that may be, it can lie seen that the variation of the speed, Vlau during the infinitely small interval of time 8/, will lie in practice, having regard to the inertia of the majses, so slight beside the speed Voj, as to be negligible in a first approximation ; and we may regard the speed V as remaining sensibly constant during the whole of the disturbance. Under these conditions, if we return to expression (7) for the variation of the central couple, we see that ttie variation of this couple enhances the stability during the disturbance, whether with a non-lifting tail we increase S, or decrease S5, or whether with a lifting tail we increase S» or decrease S,, or if we increase S.; with (o, 4- * varying alone and at remaining constant. In this last case the central couple ol the machine reduces to the single couple of the surface Sj, and we have : 8 r = L- Ks S, V- 8 (o, + t) = L= Ri 8 («, -i 0 (8) (o, -t *) In order to render the angle of attack a, constant, we can imagine a forward surface Si freely movabl? about an axis C normal to tbe plane of symmetry of the machine (Fig. 3), given value of 8 («, I •) the value of the central couple m increased in about the same proportion. Wc thus pass automatically from a couple that is already great with an invariable surface to a couple of double the »i»e when the surface is enlarged. A couple of too kilog-metres thus becom's 200 kilog-metres. The movable arrangement proposed for this cnlaigemcnt can, moreover, lie employed in the case of a mm lifting tail as a forward surface for diminishing the rear surface. The gain that it is possible to obtain in the value of the central couple by variation of surface is indeed remarkable. Ii constitute* for the machine a very powerful reserve of automatic longitudinal stability and for the necessities of practice one of the molt convenieut and perhaps the roost efficacious of the methods of stabilisation advocated up till now. Everything seem;, to show that a machine of which the design could be automatically modilicd during a dis turbance would gain greatly from the point of view of safety in flight, and that it would actually lie rendered almost completely stable. ; / 0 I" 1 ••il' •'"•< ALLIED AIRCRAFT CAPTURED BY THE GERMANS. FROM time to time official commumquls are published in the German Press giving particulars of British and other Allied aircraft which thev claim to have captured on the Western Front. The following is the list for the month of ] uly :— BterrisH AIRCRAFT. I, Caudron biplane. No. 223;, Sergt. Lesire, Mechanic Coal / B.E. biplane, No. 4106, Lieut. Wingfield, 12th Wing. 3. B.E. biplane, No. 2763, Capt. Chaloner, 12th Wing. 4. B.E. biplane. No. 2648, Lieut. Monckton. 5. F.E. biplane, No. 6365, Lieut. John Hackett Firstbroock, Lieut. Burgess. C. B.E. biplane. No. 7338, Second Lieut. C. H. A. Coxe, 2nd Wing. 7. Vickers biplane. No. ?, motor WD. 13150, Lieut. Owen Tudor Hart, Capt. G. Webbs. 8. Avro biplane, No. 2640, Cornelius van Hostcrland, 12th Wing. 9. Vickers biplane, No. 6357, Lieut, Toone, Lieut. Harvey. 10. B.E. plane. No. 949, Lieut. W. Baxter Ellis, 2nd Wing. 11. Bristol biplane, No. 5746. Second Lieut. Ha ward. 12. Morarn- monoplane, 833 A. 175, Major J. J. Waldron, 60th Squadron. 13. B.E. biplane, No. 4073, Lieut. W. J. Castle, 13th Squadron. 14. Bristol biplane. No. ?, Lieut. J. L. Whitty, Capt. VS. Veitch, 70th Squadron. 86 1. B.E biplane, No. 5765, Lieut Erit [ovett, Carpi, Johnston, ,ith Squadron to. B.E biplane, No. 2192, Lieut Hewaon 17. Macfarlandc, No.7.101. Lieut H W Nkhol 18. FL. biplane. No 6953, Second Lieul D II Mai intyre, Second Lieut. 11. Floyd. 10. Vickers biplane. No. 6949, motol A 1 D.W, 42 occupants burnt. 20. Vickers biplane. No. 6oit, Lieut. I. 21. F.E. biplane. No. 5233, Lieut. Butterworth, Lieut. MacEwen, 18th Squadron 22. Sopwith biplane, NO..OAJ3, Lieut. rletc Shaw, 23. Bristol biplane, No. 733 , birst Lieut H. Clements Finnerty, 12th Wing 24. Morane Saulniei biplane, No. ?, ('apt II '• Evans, First Lieut. H 0. Long. 25. Morane monoplane. No. ?, motor burnt, Ln-ut. Peterson !American, killed). 26. Bristol biplane, No. 2ioo, Lieut K. M. Wilson (? Wilson Brower). 70th Squadron 27. Martinsyde biplane, No. 7471, Lieut. Graham, 27th Squadron 28. Martirwyde biplane, No. 4704, Lieut I !< Farmer, 27th Squadron. A similar detailed list is also published of 20 French biplanes, making altogether, says the Berlin eommum^ui, 48 aircraft, as opposed to six German aircraft left in the enemy's hands. I
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