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Aviation History
1926
1926 - 0857.PDF
November 25, 1926 Supplement to FLIGHT ENGINEERINGSECTION Edited by C. M. POULSEN November 25, 1926 CONTENTS PAC.F •Comparative Quantities ii: Aircraft Statistics;. Ily Professor E. Everling ... ... ... ... ... ... ... ... ... 95 Aircraft Performance. By J. D. North, F.R.Ae.Soc 99 OUR CONTRIBUTORS Prof. E. Everting, whose article, entitled " Comparative Quantities in Aircraft Statistics," appears in the present number of THE AIRCRAFT ENGINEER, is a, well-known writer on aerodynamics in Germany, and it is with very great pleasure that we introduce him to our readers this week. We use the expression " introduce " advisedly, because it is an unfor- tunate fact that, although in Germany it is the rule rather than the exception for all seriously interested in aeronautics to follow closely what is written on the subject in other countries, in England we are a little apt to let the language difficulty stand in the way of our study of foreign technical literature. Tims we fear that the work of Prof. Everling. as of that of a number of other prominent German writers, may not be as widely known in this country as it deserves. We hope in the future to do our small share by publishing, as occasion affords, translations of articles by foreign writers on aeronautical subjects. Unfortunately, THE AIRCRAFT EN- GINEER is not yet. of sufficient size to allow of publishing all that deserves to be published, but we do feel that even an occasional article from a foreign writer may do a good deal towards an interchange of ideas and viewpoints. The three quantities which Prof. Everling has put forward seem to offer a convenient means of comparing the efficiency of different machines and, although the fact that throughout the article German expressions and coefficients, as well as metric units, are used will doubtless prove slightly bewildering to some, there should be no great difficulty in following the writer's arguments. The numerical values of the three quantities are, of course, those based on Continental units, but as they are intended merely for comparative purposes, this should not greatly matter. Mr. J. D. North continues this week his series of articles on " Aircraft Performance." and more particularly on structural policy in design, dealing mainly with the effect of changes in gap/span ratio. He arrives at the conclusion that a change of gap of 10 per cent, has made no difference to the weight of the wings, the increase in weight of struts having just balanced out the reduction in weight of the spars and wires. The article has been written under great difficulties, as Mr. North has been suffering from a touch of influenza, but he carried on and completed the article rather than disappoint our readers, a fact which they will, we feel sure, greatly appreciate. COMPARATIVE QUANTITIES IN AIRCRAFT STATISTICS. By Professor E. EVERLING. LIN the May 28, 192(5, issue of the Zeitschrift fur Flugiecknikund Motorluftxchiffahri (generally given in the slight! ' more convenient form l" Z.F.M.") there appeared an article entitled " Vergleichsgroszen ziir Flugzcugstatistik" by Professor E. Everling, which contained the derivation of three new quantities intended to facilitate comparison between various machines as regards efficiency. Hitherto a comparison between machines lias been no easy matter, and it was thought that the new quantities might afford a means of rendering this possible. Consequently we approached Professor Everling and the Editor of the " Z.F.M. " for permission to translate the article for the benefit of readers of THE AIRCRAFT ENGINEER, and this permission was willingly granted. The task of translating the article has been no easy one, mainly because in the majority of instances no English trans- lation existed which would adequately represent the meaning of the original German expression, and so a fair number of English expressions have had to be " coined." The Editor of THE AIRCRAFT ENGINEER does not claim that these translations are always the best possible, and will be glad to receive suggestions for improvement before some of the coined words definitely pass into the English language. The matter is one of considerable importance, not with regard to the present article only, but in aeronautical literature generally, and it is undesirable to introduce fresh expressions unless these are to be generally accepted and " standardised " as it were. Professor Everling's article, as originally published in the " Z.F.M.," contains a very great number of footnotes giving references to other works by the same author and by others. As in the vast majority of cases British readers of THE AIRCRAFT ENGINEER will not have access to these works, all of which are contained in German publications, it has not been thought necessary to quote the majority of these foot- notes. This .should not, however, be taken as proof that Professor Everling has failed to give chapter and verse for his claims, and those sufficiently interested in the details of the derivation of the three new quantities " high-speed figure," "distance-figure," and "altitude-figure," are advised to refer to No. 10 of 1926 of the " Z.F.M." As regards the use of the Everling quantities, in the future we propose to follow the example of the " Z.F.M." and give the values of these three quantities in machine descriptions wherever the necessary information is available. By adhering to the original units direct comparison with foreign machines becomes possible.—EDITOR.] 764a
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