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Aviation History
1944
1944 - 1188.PDF
620 FLIGHT JUNE 8TH, 1944 CORRESPONDENCE The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. THE "MAIL" PLANE Preventing Unhealthy Reaction ALTHOUGH I am only a medical student I can foresee several difficulties in the operation of yfeur new '' Corre spondence " Mail Plane (May 18th). « Chief amongst these is the lubrication of the main rotor axle. It seems to me that if the rotor gets at all stiff the reaction will cause the plane itself to revolve in the opposite direction. May I suggest an inverted bottle of castor oil—that should make it move. , " Z. Q." GUNPOWDER v. PETROL Laws of Thermo-Dynamics " "P\RJVER" has evidently been blinded by the smoke-laden •*-' flash of his own gunpowder, which may perhaps explain why he conveniently ignores the laws of thermo-dynamics as propounded by Joule and others which established that energy, or work done, is directly related to the amount of heat generated, i.e., calorific value; thus, one British Thermal Unit is equivalent to 778 ft./lb. of woik, while the production of l horse-power requires a heat expenditure of 42.44 B.T.U. per minute (assuming 100 per cent, thermal efficiency which, of course, is not achieved in practice). Now the combustion of gunpowder may be represented by the following chemical equation: — 2 K NOa-T-S-^ 3C = K3S-=-N,-f-3 CO, Using the above as. a ba^ta, it can be calculated that 1 lb. of gun powder produces 5.3 cu. ft. of gas at normal temperature and pressure. Howevei, if we assume a theoretical combustion temperature of 3.400 degrees C.—although in practice this would probably Only be about 2,000 degrees C.—this volume becomes 66 cu. ft. (vide Charles' law). The combustion oi petrol may be repiesented as follows: — 2 CaH„ + 25 C2 -i- 94 N2 = 16 C02 -j-18 H20 + 94 N2 The gases produced by the combustion of 1 lb. of petrol and the theoretical amount of air have a volume of 200 cu. ft. at normal temperature and pressure and at the theoretical com bustion temperature of 2,350 degrees C. this becomes 1,720 cu it. If "Driver" follows the foregoing he will gather that at the theoretical combustion temperatures, a given weight of petrol has twenty-six times his "piston-pushing value" of an equal weight oi gunpowder. Thus a heavy bomber which at present may take off with, say, 14,000 lb. of petrol to carry a sizeable load of bombs to a distant target would, if using gunpowder, have to carry a fuel load of 364,000 lb,!. I will leave "Driver" to estimate whether even a Lancaster could cope with this and a bomb load. As to the question of relative cost, since kerosene would be suitable for the type of power plant suggested by "Driver," this could be reckoned at about id. per lb., which I am sure must be only a very small fraction of the cost of gunpowder even when mass-produced on a large scale. A. R. OGSTON. "Horace " Has His Say DRIVER" has suggested that gunpowder is superior to petrol as a fuel (Flight. March t6th). In a criticism of Mr. A. R. Ogston's letter he asks for the relative costs per lb There is some reason for hoping that too octane petrol will be sold to commercial users for 2jd. per lb. after the war. However, let us take 3|d. as the present cost of Pool spirit. A pound of gunpowder as used in the present austerity shot gun cartridges costs the trade 7s. 3d. per lb., so that with profit and sales tax added the comparable price will be, say, 9s. gd. per lb., i.e., 36 times as much as petrol. As the energy content of petrol is 15 times that of gunpowder, this means that one shillingsworth of petrol will take us 540 times as far as twelve penn'orth of gunpowder whether we travel by aircraft or motor car. To illustrate: Our 1927 (late) Morris Minor does just 20 miles on a shillings- worth of petrol. If we installed a gunpdwer engine it would do 65 yds. on the same expenditure! Horace, our tame Stressman, says it would require 12 tons of gunpowder and would cost us about £1,350 to propel the Morris from Land's End to John o' Groats. He says we would get into trouble with the police. He says we should have to re-powder our tank, and maybe our noses, every two miles. Ht does not think we should enjoy sitting on half a keg of gun powder any more than sitting on a volcano. ' However, this journey from Land's End to John o' Groats is manifestly impossible as our savings would be burned up by the time we reached Penzance! Our Stressman says that the expressions used in the previous correspondence, i.e., "calorific value," "piston pushing value," "expansion upon combustion," "heat content" and even "expansive economy" (whatever that might be) mean precisely the same thing. He says they mean the amount of energy available in the fuel, which is surely the measure of its ability to do work. Horace says that Mr. A. R. Ogston in his very scholar] y article is absolutely and completely right. He says that to use gunpowder would be expensive economy. Undoubtedly, Aviation is the Coming Thing! W. S. SHACKLETON. j THE FUTURE OF CIVIL AVIATION Dangers of Race for Supremacy SINCE we are now starting to make preparations for civil aviation in the post-war world, and since it is the expressed desire of all the peoples of the world that there shall be a lasting peace, it behoves us to consider how best we can serve this aim. To be quite frank about it, it is obviously in the interests of all readers of Flight that this country should generously spend its money and effort in the pursuit of aeronautical research and the maintenance of large up-to-date air transport fleets. Such a course would clearly bring immediate prosperity to the in dustry and all in any way concerned with aircraft. But we should ask ourselves whether, in pressing for a large aircraft industry, we were really working for the ultimate peace and general prosperity that mankind as a whole is seeking. There are two aspects of this question: one, that of national prestige; and the other, that of the relative priorities of our various efforts to improve the standard of living of people generally, in accordance with the principles of the Atlantic Charter and the recent Philadelphia Charter. If we build large, fleets of luxurious airliners to compete with similar fleets of other nations, <^e must be careful to see that we are not drawn into a highly expensive and bitter race between the nations for air supremacy. Such a course, besides being extremely uneconomical, involving the country in vast expenditure, has the danger of being a breeding ground for international ill-feelings which can so easily menace the peace. There are already indications that this race is beginning. Before it is too late, while an active spirit of co-operation exisjgk between the United Natioqs, brought about by fighting*!** common enemy, we should do our best to come to some agree ment with other countries for the setting up of a rational and economical air transport system for the world. We should do well to study the means of obtaining internationally operated airlines on a regional and world-wide basis. The other aspect of the matter hinges on whether we are putting the development of aviation too high on our list of priorities for post-war reconstruction. Would we be honestly justified in spending too many millions a year on aeronautical research and airline subsidies, before—to take one example— we had solved the problem of providing adequate nutrition for all our countrymen ? Sir John Boyd Orr has told us that just before the war one-third of our • population did not obtain, a diet adequate for health. •» I feel that we aeronautical people, and, indeed, those in other occupations, should periodically pause to consider the social consequences of our work in relation to the whole national and international effort. In the conclusion to his Wright Brothers lecture, Mr. Farren said he hoped that the work of aeronautical research would be put to better uses than for war, but he also confessed that an absolute scale on which to base the value of his scientific efforts eluded him. All honest and eminent research workers are bound to seek this absolute scale of value, but it is socially desirable that they should also understand the position of their work in relation to all the efforts for national progress, so that they can appreciate why moneys which they would like to f« spent on particular items of research may in peacetime be us>? for other purposes. • F. GRINSTED.i
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