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Aviation History
1917
1917 - 1342.PDF
D3CEMEER 2O, time'it from the moment when sighted to the moment when vertically underneath, measuring the angle turned through by the tube. In Fig. 2, let b = height of machine in feet. s =horizontal distance between machine and object in feet. 4> = angle in degrees which tube turns through. v =• velocity of machine relative to earth in m.p.h. /=time taken in seconds. • , - . 60 - : '. t 88 *<:.-'_Then «r- But s = h tan <t>. 60 ft tan» 88 X t~~,, _ 0.68a. *-* If a standard angle of 360 10' were always taken for <f>, we have :— v = 0.682 x 2/ h x 0.734 t (b) The difficulty of filling in and working out the values of equations (a) and (b) with different sets of values, can be got rid of either by using a graph, a table, or a slide rule. It is not difficult to arrange a slide rule on which the unknowns can be read instantly with one setting. The latter method has the advantage—if its use is practicable when flying—that any combination of the unknowns can be solved instantly ! The principle of a suitable ruler is the same as that of the standard Mannheim type. The scales are arranged as in Figs. 3 and 4 on the front and back face respectively. / vFront face for solving 8 = tan -»( 0.366—j~ \ v» Scale A on bottom edge of top strip of ruler is a scale of degrees. Scale B on bottom edge of middle strip of ruler—the slide— is a scale of heights in feet. Scale C on top edge of bottom strip of ruler is a scale of velocities in m.p.h. To work ruler, suppose for example :— v—go m.p.h. and h = 2,000 feet. / v \ , / „ 90 \Then 8 = tan"' .366—™ - tan ~ ' .366 — 1. V Jh J V v/2ooo / To v, i.e. 90 on scale C, set h, i.e. 2,000 on scale B, and read 6" over index on scale A. 8 — 36^° approx. The method of calibrating the rule is as follows. Scale B is half the length of C, and therefore the heights, although marked as h feet, represent actually Jh feet. The first operation therefore divides v by Jh. The multiplication of this fraction by factor .366 is done by placing scale A— before being marked into degrees—.366 units to the left. Back face, for solving <f> = —. zt Scale A on bottom edge of top strip of ruler is a scale of velocities in m.p.h. Scale B on bottom edge of middle strip of ruler—slide—is a scale of seconds. Scale C on top edge of bottom strip of ruler is a scale of height h in feet. To work ruler, suppose for example :— h = 5,100 feet and t= 30 sees. Set 30 on B to 5,100 on C and over index on A read 85 m.p.h. <$> <$> German Bomb Factory Destroyed. ACCORDING to the Svenska Dagbladet, a -big ammunition factory, which mainly manufactured b' mbs for the use of Zeppdins and aeroplanes, has betn bkwn up near Kiel. All the factory buildings, as w( 11 as 1h< railway station, close to which th<y stood, are 5aidtohav< been burnt to the ground and the railway line destroyed to a length of several hundred yards. A number of people w< re killed. An Explosion at Friedrichshafen. A MESSAGE from Zurich states 1hat an explosion occurred on December 14th at the Zeppelin works at Friedrichshafen, as the result of an accumulation of gas becoming ignited. A number of persons were injured. Poisonous Soup from Raiders. A MESSAGE from the Daily Mail correspondent in Paris states that during the last air raid on Calais the Germans The calibrating is executed by making all scales the length, thus the value of in the equation v = - - - is given t it under 10 on scale B and also scale A. Division by 2 is made by placing indices .3010 units (of the slide) to left before being marked with numerals. A very suitable unit for the scales is 2 cms.; this brings the total length to about 8 inches, a very convenient size. Description of the actual sighting and dropping apparatus has been so far purposely avoided, as it is hoped that the reader has for himself, by this time, got a fair idea of their nature and functions. No special dropping mechanism is required, but it is essential that the axes of the bombs are perpendicular to the normal flying axis of the aircraft, and immediately under the pivot of the sighting tube. To ensure that the machine is flying in the plane of its normal flying axis, the pilot must be provided with a service- able spirit level, placed horizontally with this plane. The sighting apparatus must be in the nature of a telescope, capable of being rotated clockwise through 900, i.e., from horizontal to vertical position. The angle of the line of sight to the vertical—angles 8 and <f>—must be indicated on a dial or graduated ring. An alternative arrangement is the rotating prism and universally jointed sighting tube, of the " Goerz Range Finder." For calculating the value of v it is obvious that a stop watch synchronised with the turning motion of the standard angle—suggested 360 10'—would be an advantage; otherwise it would be necessary to time the angular rotation by hand. In any case, timing mechanism must be included to complete the whole apparatus. Here is another opportune moment,to point out the field for an ingenious instrument maker. If, for instance, it were possible to read the angles 8 and 0 and the time t sees, with- out removing the eye from the eyepiece, it would save time and increase the accuracy of the results. Application,—Having described generally the main details, it will be as well to follow through with the exact procedure on a deliberately planned raid. As a precaution beforehand, the state of the atmosphere is taken and approximate height of flight decided upon. From a contour map the height above sea level of objective is taken, which will be deducted from height read on aneroid some time before reaching target, thus giving value of h. The next thing to do is to calculate the value of v, to do which the pilot will first steady the machine as much as possible, keeping it flying straight ahead and in its natural flying plane. The observer will next sight a distant object in front, and keep it in view until perpendicularly under machine, recording time in seconds taken, and angle sight tube has turned through ; from these values v is cal- culated by equation b. With this value of v angle of release 0° is calculated by equation a, and sighting tube adjusted to it and locked. The machine will now be approaching target, which will— providing that a straight course has been kept—app ar in sighting tube. This is the moment for releasing the bomb. In the " Goerz Sighter " this right and left or third motion of direction, is corrected by universally jointing the range finder, and making the rotation caused by machine turning to right or left be indicated to the pilot by a sensitive electro- galvanometer. It is very obvious that, before it can bs said how useful these apparatus will be to aviation as a science, many practical experiments must ba carried out, and this together with the perfecting of the instruments and the finding out of the necessary corrections for wind and drift, are problems left to the practical aaaa. dropped not only 100 b">mbs but also a number of small packets b aring an inscription in English to the tffict that thi y con- tained soup powder. Directions wire given to dissolve the powder in cold water and then to add a pint of bailing liquid. Analysis has shown that the pack ts contain an extremely violent poison, and the Temps states that all the families who took the soup have died. In Eastern France a numb r of children have b en killed by poisoned sweets and explosive pencil-cases dropped from aeroplanes. . . . -...: Demand for Aeroplane Workers. * DURING th hi aring of a cast before the Russian Tribunal, at Caxton Hall, on December nth. Sir Edward Smith, who presided, referred to the big d< mand for skilled work< rs in aircraft factories. He knew that in one factory, which now employed 2,000 men, it was proposed to increase the numbsr to 5,000 in the next six months. 1343
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