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Aviation History
1915
1915 - 0114.PDF
THE ZEPPEL COMING from the pen ofso well-knowna French writer on aeronautical matters as Mons. Georges Prade, the following article on the above subject, which appeared in J.e journal of the 2nd inst., has much of inteiest for our readers, and all those who are at all perturbed at the thought of the " frightfulness" which the Germans promise to perform by means of their airship fleet. M. Trade's views are as follows :— " The Zeppelin question has become to a certain extent—and, psrhaps, entirely so—the question of the day. After not having believed sufficiently in the Zeppelin, there are now people who believe too much in it. Permit one, who has followed the matter from the first, and who has appreciated the splendid efforts of Count Zeppelin, to examine, figures in hand, and in the light of cold reality, the probable actual state of the German aerial fleet, the nature, value, and number of iis units, ihe possibilities and the exact conditions of a raid on London or Pari-. Our readers will pardon us for being exclusively technical, and for quoting figures. But there is no serious study without precision—without figures. " The real offensive value of the German aerial fleet is the sum of the efficiency and number of the units that compose it. Let us, therefore, establish these two points, and commence by defining what a modern Zeppelin is. The imagination has been given free play on this subject, and, as if the Zeppelins were not already monstrous enough, rumour has made them even larger. Some writers have gone >o far as to talk of 'super-Zeppelins' of 400 yards in length, which presumes a trifle of 300,000 cubic metres. It can be stated without hesitation that the modern German dirigibles are of the same tonnage as before the war, which is, of ourse, necessary for their rapid manufacture. Material proofs of this statement, of which the first, sufficient in itself, is the actual dimensions of the German sheds, are obtainable. The longest shed in Germany, that at Leipzig, is 193 metres, and those at the works of Friedrichshafen, which have not yet been enlarged, are 178 metres long. The rotatable shed at Cuxhaven, which cannot be enlarged, is 180 metres. Those at Cologne, Metz, and Baden are only 158 and 160 metres. The French hangar at Maubeuge has lately been enlarged to 160 metres by the Germans. The two 1914 types of Zeppelins measure:—The 22,000 cubic m. army airship, length, 156 m. ; diameter, 14*8 m. ; width over the propellers, 22-5 m. ; and height, i8'8 m. The 27,000 cm. naval airship, length, 158 m. ; diameter, 16-58 m. ; width over propellers, 22'8 m. ; and height, 19 m. These figures represent, therefore, the maximum size airship which will enter the actual German hangars. It has been possible to improve their economy, but their tonnage, and consequently their radius of action, useful load, maximum attainable height, and speed are the same to-day as they were in July last. This radius of action is sufficient not only in times of peace, but also in war time, as evidenced by the Cuxhaven-Yarmouth-Cuxhaven raid. The length of this was 730 kiloms., or equal to a cruise from Frankfort to Paris and back, or Cologne to London and back. Airships of the same type and carrying the same load can, therefore —theoretically, and speaking from the aeronautical point of view— repeat the performance, Starting out from a sufficient number of sheds. " What are these airships ? What weight of bombs do they carry ? We know that the Germans have naval airships of a known type, and of 27,000 cm. capacity. Let us first attempt to calculate their load of explosives, as this will serve as a basis for the estimates of modern ones. " Let us state, first of all, that the lessons of experience (the bom bardment of Antwerp, Ostend, Ghent, of the Belgian campaign, of Warsaw, Plosk, Nancy, the English coast, and Libau) have up to now been very reassuring. In each case there was no real bombardment, and the cruisers of the air, which were the same in numbers as at Yarmouth (two or three) have dropped few bombs, bombs, moreover, which were of light weight and small effect. There were twelve deaths at Antwerp, not a single one at Ostend or at Ghent; 40 deaths from five bombardments in Poland, 2 at Nancy, 4 in England. This gives a total of about 60 victims, that is to say the crews ot two large Zeppelins, all in six months of campaign ing, and after fourteen attacks, during which period the flotilla lost at least five units. Nowhere have bombs been found weighing more than 49 kilogs. (this was the weight of the bomb found intact at Yarmouth). " The estimate of the useful load which a Zeppelin will carry will explain this mystery, which cannot be ascribed to Teutonic modesty. " The Germans have carefully withheld these figures from us. In the German Taschenbuch of the aerial fleets, the useful load of Zeppelins does not appear. We have, however, fairly exact data to go on. The first were furnished at the time of the landing of Z-4 at Luneville in April, 1913. This airship was of the 19.500cu.rn. type (141 m, by I4"8 rn.). The total lift was therefore about 20,500 FEBRUARY 12, 1915. N QUESTION. kilogs., but the ship's books showed that the dirigible itself, frame work, fabric, motors (three Maybach of 180 h.p. each, and each weighing 448 kilogs.), only left available a lift of 4,800 kilogs., which works out at 23-9 per cent, of the total load. " From these 4,800 kilogs. must be subtracted 950 kilogs. for the crew (twelve men), and 135 kilogs. of petrol and oil per hour, which make--, for a six hours' cruise (360 kilometres), 810 kilogs. Finally, in order to reach a height of 1,900 m., hardly a sufficient altitude, Z-4 had to jettison 3,000 kilogs. of ballast. The Z-4, therefore, had exhausted its whole useful lift in a six hour:,' cruise and covering a distance shorter than that from the nearest German shed to Paris or London and back, without counting projectiles, ammunition, armament, and personnel. It can therefore be stated that, except by flying very low, and thus running the risk of being brought down, the Zeppelins of the 19,500 cu.m. capacity or less, are unable by far to solve the problem. " It is for this reason that Germany in 1913 constructed types oi 22,000 cubic metres capacity, 156 metres long by i4"8 metres diameter, that is to say, of the same diameter as the older ones, but with two more ballonets(l8 ballonets instead of 16). The power and weight of the motors is the same, as is also, for all practical purposes, the speed. Nevertheless, the weight of the gas chamber has been increased by two ballonets, and the following estimate can be made : The weight of the gas-chamber and of the keel has been increased by about an eighth, a weight which has to be subtracted from the extra lift of 2,600 kilogs. furnished by the increase in cubic capacity. Further the extra weight of fuel for four hours which is required in order to give the dirigible the necessary range of action for the raid in question (ten hours' cruise of 600 kilometres) has to be subtracted. This is an addition of 540 kilograms which brings the total weight of fuel up to 1,350 kilos. A crew of twelve men is insufficient, especially in view of the fact that the dirigible is to be fitted with machine guns and gunners. The 27,000 cubic metre type had 28 men on board (the number of victims in the catastrophes that overtook L-i and L-2). If, in this case, we only take 18 men, that would be an extra load for the crew of 500 kilogs. Then we must subtract the weight of the machine guns, of their ammunition, of two searchlights, and of the sheet steel armouring for the motors, which is 2 millemetres thick and weighs 14 kilogs. per square metre. " We therefore see that the 22,000 cubic metre type with full war equipment and bound for Paris or London cannot carry anything like a ton of explosives. " There now remains the 27,000 cubic metre type, which has theoretically 6,000 kilogs. more lifting capacity. But it has a diameter of 16-58 metres instead of I4'i8 metres, and is 158 metres long instead of 156 metres. It has four motors of 180 h.p. each instead of three, and a crew of 28 to 30. The first Zeppelin captured at Warsaw had 30 men on board. The expenditure in fuel increases by a tenth. The figures given by the Maybach Works, which are, however, a minimum, give 229 grammes of petrol par horse-power hour and2'5 kilogs. of oil per hour for each motor. " Tfle raid on the English coast represented, out and back, a distance of 732 kilometres and a cruise of more than twelve hours' duration, since the L-3, the record breaker, with a maximum speed of 70 kilometres per hour, has never been able to do more than an average speed of 60 kilometres per hour, which will give, including the reserve of fuel necessary in case of wind, 14 hours' fuel, or 2,268 kilos, of petrol and 140 kilos, of oil—a minimum of 2,308 kilogs. " Let us now work out these supplementary loads ; 500 kilogs. for the fourth motor. In the L-2 there was one more boat. In the L-3 the second rear nacelle has been enlarged and the central cabin and the keel retained ; say another 500 kilogs. Increase in gas chamber Ands, meaning at least 3,000 kilogs. ; increase in ballast take 500 kilogs. (The L-3 had to leave eleven men of the ordinary crew on the ground in order to be able to increase the attainable height from 420 metres to 3,125 metres, the Zeppelin record, established on May 16th, 1914. This gives an extra height of 2,700 m. climbed in 3 hours 30 mins. at the expenditure of a special discharge of 1,000 kilogs., including the weight of the eleven men of the crew.) " Weight of supplementary crew, 600 to 800 kilogs. TotJ, 6,100 kilogs., which, even by reducing the ballast and crew, gives us the same weight of explosives, 1,000 kilogs. at the most, transported it is true, a longer distance, 730 kiloms. instead of 540 kiloms. " The large naval dirigibles which appeared over the English coast certainly had not 1,000 kilogs. of explosives on board, which is proved by the fact that they did not throw that weight. I do not suppose that they would have carried their bombs back to Cuxhaven. These weighed at the most 50 kilogs., and each carried at the outside 20 bombs. Other figures confirm this estimate. Six bombs were II4
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