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Aviation History
1916
1916 - 0909.PDF
OCTOBER 19, 1916. i/QGHTj A1 SSCDfefcS // in doubt about anything aviatic, write to " FLIGHT " about it. J. B. W. (Monkseatonl. You are quit*- right in flaunting that a rotary engine has a gyroscopic effect on an aeroplane when turning Not only has the engine, hut also the peropeQw, -> gyroscopic effect, and it will even frequently be found that the effect o! the propeller is greater than that of the engine. A numerical example will help to illustrate the magnitude ol this gyro scopic couple. Let us take a rotary engine of 100 h.p., and assume that it is installed in an aeroplane riving at 100 m p.h., and further, that the machine makes a turn in a complete circle of 41x1 ft. diameter. The gyroscopic couple is then expressed by the equation M «. mA*wA. where m •» mass weight ot engine-r-gravitv. Taking the weight of u too h.p. \V 280 rotary engine as 280 lbs., we have m — — — —— — 8-; 5. A— radius of gyration of engine, which we shall take as 1 ft. » m angular velocity of rotation, in radians per sec., and fl •• angular velocity Of displaced axis, in this case the aero plane's rate of turning. If we take the number Of revolutions , .. • 1,200 of the engine as 1,200 per nun., we have «/ - x 2» — 125. As the machine flies at 140 ft/sec and describes a circle of 200 ft. radius, it completes one circle in 2x3-1416 X 200 „ . 2* 146 Substituting- in the i« Si, sec. a formula we have gyroeeopU couple - M — 8-75 x t* x 125 x 0-73 <- 798-4. The gyroscopic couple is therefore 798-4 lbs. ft. If the area of the elevator is i 3 sq. ft. and acts at a distance of 20 ft., the turn in question imposes a load of about 40 lbs. on the elevator, or Mart) 3 Ibs./sq. ft. It should be pointed out, however, that the fixed tail plane carries its share of this load. If the engine revolves clockwise fas seen from the pilot's seat), the effect of the gyroscopic couple in a left-hand turn will be a tendsni j for the tail to drop, a right-hand turn having, of course, tin- reverse effect. There are various advantages in multi-planes over biplanes, for the same reason that when a certain limit is reached the biplane construction is preferable, from the point of view of strength to weight ratio, to the monoplane. Thus, for very large machines, where it is desired to keep the span within reasonable limits lor purposes of housing and other considerations, it may become common practice to resort to the multi-plane formation. Even for small machines there would appear to be certain advantages in employing three or four planes instead of the now usual two. lot instance, although there is a certain amount of interference taking place with superimposed planes, this is partly countei - acted by the fact that if each plane of a biplane is divided into two of the same overall span, the chord of each is halved and therefore the aspect ratio doubled. Also, in a narrow chord the travel of the centre of pressure is shorter, and it may become possible to use one strut only where a pair was formerly employed, thus saving resistance. We cannot say for certain what is the maximum attainable height for a modern Zeppelin with full load: probably some 15,000 ft. H. B. (Fareham). The disposition of the engine gondolas on the latest Zeppelins is not quite clear, but it appears that there is one in front, rather elaborately constructed with covered-in sides and top, and providing accommodation for the com mander and helmsman. The engine of this front gondola, as far as we can make out, drives «. single screw placed behind the gondola. The rear gondola appears to have contained three engines, two of which drive the side propellers, while the third drives a stern propeller. The observation car, when not in use, is probably placed in a recess in the keel of the main hull, so that the observer can enter it through a trap door in the communication passage running from the front to the re.u madolt ' »me niMile th. observation car, he, would close the little trapdoor m the rOof through which he red and gi\. the signal to 1* let down. With regard to the swinging ol th • ,,n the -.lability >4 the airship, the car is fitted with tin* *o .. bead to the wind, HO that probably there 1* verj liith ^winging The numlwr of baUoanets that would have to I- before the airship descended would depend on wh. th. I was loaded 01 not at the time it light, one at two ot the balloniuts ( uuld ^lrobablv be ni-ath emptied with. sarily forcing tin airship down, as hci engine* would hi rapport hei nia the side propaltern, h. B. (Horsham). A brief consideration will show wh\ .1 \ei\ efficient in may Ite more dMgefOOl than a less eltn 1. tit .suddenly flattening out all. 1 I ••• Sttppow- ihal MM RUM lime Hies at a speed ot V m p i> , and bai at thai | 1 a gliding angle ol 1 m S, If 1 hint is dived win the earth's attraction is equal to the weight of the machine (W) The speed of th* machine oathi vertical dive (with tht engine switched off; will ionium- !.. in.i..w until the rrsist- ance 1 o\V is increased to w . II the tettstana increase as V*. the velocity U which tbj rotlttanot >• 1 to W is v/oV n 2 45V In other word*, the maximum speed OS I dive, with the engine switched off, ts 2 • 4c; titan the normal (lying speed Now, suppose that it is liuetfbh to cut down ir.m.imc without alt-'img auv Othtt ,,| il><- aero plane's characteristics until the gliding angle becomes I in u. By the same reasoning as in the hisi oaat. the velocity at which resistance becomes equal to W is s/"iS% t-t'-i^ It will N- easily appreciated that a sudden flatti ninn out will impose far greater stresses on the lattat mat bine than on the formal We have even known designers who kept up body resjstancr for this reason, although in modern timet and with careful piloting there is no neceasity, nor apparently any in y, to do so. Airman (Portsmouth), The pay ol a hiving ( lilner is 1 II plus I living pay ; WBM training 7s. f>rf a day The kit allow tm an officer appointed to tin Special Keserve. G.W.F. iKedia.i See reply to " AIHMAN " above. Apply to the 1 General of Military A. loiiautn -,. Adastr.d Houte, London. I 1 , lor the necessary tonus A. B.C. (Cheltenham). We understand that up to the present there has been no need so provide Cm ih. contingency you suggest li officer's services 000W BOf 1« utilised 10 any way. no doubt would !*• invalided out of (he Service. JMew Reader (Dublin), A copy ol 1 in.in for December 10th, 1915, with seals drawings and description of the Fokfcer moiioplanc, can still be obtained, price 3^. pt»t free. F. B. (Curragh). There are no special qualifications, and you should apply in the usual way for a transfer to the It, IT n an Ob • rvw If your application is granted you will be teat to B school lor t course of training Vour experience should certainly assist you in your application. M. (Norfolk). The badge signifies that the officer is a qualified Observer attached to the I; I ( I he grounds you mention are Government training centres, and that explains why no refer ence can be made to the flying there. 8. G. T. (B.E.F.). Apparently, a* the injury was caused by an accident, you would not be entitled to wear the gold stripe. 90S
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