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December, 1940 AIRCRAFT ENGINEERING 351 This only shows that the matter is not easy and, however desirable from several points of view, standardization must not be allowed Aircraft Engineering to run riot and cause a blind alley. In the realm of production, we have in recent months frequently pointed out the value of solid well-designed jigs and their value in actually simplifying the change-over to a new type, provided that they are capable of adaptation. Otherwise, of course, they only make the starting of work on the production of a new machine Editor: Lieut.-Col. W. Lockwood Marsh, F.R.Ae.S., M.S.A.E., F.I.Ae.S. a more lengthy and laborious process. We do not presume to judge the matter or to lay down the law on the subject. The question of when, and how much, to standardize is extremely difficult. We do, however, consider that it is one that merits more consideration than has perhaps been given to it and, for the purpose of starting discussion, decided to publish PERENNIALLY thorny subject, which never fails to arouse acute controversy whenever it is broached, is MR . THOMPSON'S paper. Although there is a good deal of detail standardization. Some hold the view that all standards in it which only applies to the American industry, we do feel that are merely clogs on progress; while, at the opposite extreme, it presents the case for standardization more cogently, on the whole, than we have yet seen it put and therefore deserves the- there are those who would cut down, for instance, the number of careful perusal of British readers. permitted specifications for materials to a tenth, or less, of those that at present exist. The main difficulty is, of course, that, very naturally, any individual will consider that the specifications he is THE "HANDS " OF AIRSCREWS in the habit of using himself are all that is necessary and he feels IT IS CURIOUS how a turn of the wheel has again brought up that others are merely being obstinate in preferring different the question of the direction of rotation of the airscrews of twin- materials. The number of specifications that have to be available engined aeroplanes. Years ago—for a reason, the effect of torque, for use entirely, then, depends on the number of individuals—and quite different from the present one—engines were made in right- perhaps their varying degrees of obstinacy. hand and left-hand form for fitting in twin-engined machines so The above of course applies to standardization as it affects an that the engines, and airscrews, should rotate in opposite direction. industry as a whole. But there is also the more limited form of This practice fell into disuse but has recently been revived owing to standardization within the confines of the practice of an individual realization of the effect of the slipstream rotation inpinging on the firm. Only too often—though naturally less frequently now than tail surfaces in affecting the stability of the aeroplane. a few years ago—when a new type is developed every part or fitting We publish in this issue a Ministry of Aircraft Production transla will be specially designed anew for the particular aeroplane, regard tion from a paper published in the Jahrbuch 1938 der deutschen less of the fact that a large proportion of those already incorporated Luftfahrtforschung—which is an almost inexhaustible mine of in the previous design might well, with a little adaptation, be information on German research work and engineering practice— made to serve the purpose. giving the results of an extensive series of experiments, in the wind- It is primarily with this aspect of standardization that MR. tunnel and full-scale, made by the Dornier-Werke on the relative THOMPSON, of the Glenn Martin Company, deals in the Society of merits of what we should call inwardly and outwardly rotating Automotive Engineers paper we publish this month. In parenthesis, airscrews from the point of view of stability. Unfortunately, we may call the attention of our readers to the title he holds in his throughout the paper terms "upwardly" and "downwardly" firm's organization—that of "standards engineer." We do not rotating, which are rather obscure, are used and the exact meaning know whether this designation, with all its implications, is a of them is not explained till the end. It may help the reader, there common one in the American aviation industry or how many firms fore, if it is made clear here that the reference is to the motion of in Great Britain have on their staff an individual charged with the airscrew blade in relation to the main plane in the region between corresponding whole-time duties. It at any rate is an indication the axis of the airscrew and the fuselage. In other words, an of the importance one firm attaches to the matter. It appears "upwardly " is an "outwardly" rotating airscrew while one possible that much saving of time, not only of the design staff but revolving "downwardly " is, as we should say, rotating "inwardly." in the production of aeroplanes, might in fact be saved if a small The general conclusion is that, particularly from the point of view department of this nature were set up in those firms which do not of longitudinal stability, the former direction of rotation is pre already possess one. To rely upon memory, when preparing the ferable. It is interesting to recall that, in a note on the subject detail design of a new type, to recall whether one or more of published in AIRCRAFT ENGINEERING in April 1038, PROFESSOR probably several thousand small parts of an existing type could STALKER indicated the opposite conclusion. He, however, was not be incorporated in the fresh design is obviously not very trust considering the effect of the rotating slipstream on the main plane worthy. On the other hand, the change-over from production of itself and pointed out that the outwardly (or "upwardly" ) rotating one type to production of the new model, and the putting into stream increased the effective angle of incidence and so led to manufacture the production-model of an experimental prototype, an earlier stall; whereas the Dornier experiments were concerned would obviously be greatly speeded-up if such information were with the effect on the tail planes. It looks as if further organized ready at hand with one individual charged to watch over this research were needed to elucidate the position more clearly so as to matter and this alone—to say nothing of the saving in cost in being ascertain quantitatively how far the one effect may neutralize the able to give merely a repeat order for a further supply of parts from other. One of the incidental results of the Dornier experiments, a sub-contractor who has already been turning out large quantities which is strengthened by PROFESSOR STALKER'S conclusions, is the of them. advantage of the pusher installation of airscrews—a consummation This form of standardization must of course be used with devoutly to be wished for many other reasons, though still un intelligence or it may indeed become the "master " and affect the attainable from other even more potent causes. progressive character of new design work. There is no doubt, I t is, meanwhile, interesting to note that all recent French for example, that the Germans, in their anxiety to steal a march twin-engined aeroplanes were fitted with oppositely-rotating air on other nations by rapidly building up a large, and as they screws, as are some Italian—notably the Breda 88, as was mentioned hoped dominant, air force, "froze" their designs too soon. A when it was described in these pages in August this year, the "hand " striking example of this is the Junkers J u 87 dive-bomber, which, of which is inward. Most notable in this connexion is the Lockheed as the world now knows, was in fact obsolete before it ever came P.38, because in the experimental prototype the airscrews were into action against efficient and modern fighters. The mistake inwardly rotating, while in the production model this has been there made was in designing a machine for mass production made reversed. We do not know the reason for this, but it is presumably up of parts and assembled by methods which were not adaptable the result of experiments, though we are not aware that these have to another type. In such an instance standardization became over- been published. specialized and merely became a halter round the neck of the designer.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Dec 1, 1940
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