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Aircraft Engineering THE MONTHLY SCIENTIFIC AND TECHNICAL ORGAN OF THE AERONAUTICAL ENGINEERING PROFESSION VOL XVIII No 206 APRIL 1946 has set an example to others. We do not know whether any similar symbols were used in Germany, or other countries, but judging by AST month we had occasion to comment adversely on the lack various handbooks we have seen, no comparable attempt appears to of standardization which characterizes domestic electric equip- have yet been made in the United States. They seem to cling to L ment, while congratulating the S.B.A.C. on its pioneering lead elaborate pictures portraying the details of each component, which in standardizing the electrical components and installations in air in some instances to achieve clarity call for the use of a number of craft. There is one field, however, in which the electrical industry colours. These have, of course, a very pretty and, at first glance, has set an excellent example. For many years now drawings of attractive appearance, but they require much more study if they are to electric installations of all kinds have been rendered admirably in be read intelligently and the required information extracted. Further formative and easy to read by the use of a standard set of symbols, more, they make reproduction except by an expensive multi-colour which have received wide currency and consequently have become process impossible, whereas the British symbols are readily reprodu familiar objects even to the amateur. cible from a simple tracing in an ordinary blue print. Largely owing to the personal efforts of MR . HODGSON, who con The MINISTRY OF AIRCRAFT PRODUCTION are to be congratulated tributes an interestingly educative article on the subject in this issue, a on sponsoring the scheme. similar happy state of affairs has been reached in connexion with hydraulics. In many ways a diagram of a modern hydraulic in Testing Technique stallation in an aeroplane bears a resemblance to a similar drawing of URIOUSLY enough, another article in this issue records electrical accessories—in one instance, at any rate, a descriptive a development in static test technique in which Great Britain term, "accumulator", even being borrowed from the other system. Cagain appears to have got ahead of other countries. To quote The run of the various pipes carrying power from the hydraulic America once more, unless examples of similar methods have been motor to the various valves, pumps and jacks is very similar on a withheld on security grounds, from the most recent photographs of diagram to the layout of electric leads and the main difference strength-testing equipment in that country that we have seen, it between the two, from the point of view of diagrammatic representa would seem that the time-honoured method of loading with shot tion, lies in the fact that the components are mechanical instead bags the structure to be tested in an inverted position is still current of electrical in their mode of operation. The problem was, therefore, practice across the Atlantic. mainly one of the precise symbols to be used to differentiate between It is hardly debatable that the more up-to-date system that has various types of component—a rotary from a plunger-type valve, been developed at Farnborough, described in this issue by MR . for instance—though there was also the necessity of dealing with the HOTSON, evinces a great advance. individual and peculiar phenomenon of various types of flow— In brief, wing specimens to be tested at the ROYAL AIRCRAFT continuous, uni-directional but not continuous, and two-way. ESTABLISHMENT are now mounted in a frame in normal position— Obviously there would initially be room for widely divergent opinions that is to say, with the top surface uppermost—and the loads applied on the precise shape and form of the symbols to be adopted. There by upward pulls through a system of levers and linkage permanently would be no doubt a school, for instance, which would cling to the established in the top of the frame; the applied load being measured original idea of making them more or less pictorial representations hydraulically. of the actual shape and function of the components. In view of the Like many other set-ups the precise details in the latest practice inevitable necessity, however, of simplifying these—unless they were have been gradually developed by trial and error and the series of to occupy an unconscionable time a-drawing and call for too photographs illustrating the article show the historical process. large a scale in reproduction—this line of thought was evidently, and It is obviously a subject which does not lend itself to photographic wisely, abandoned and a more formal, and in some instances depiction and unfortunately the details tend to become merged one arbitrary, type of delineation adopted. into another in the process of reduction for reproduction purposes. Parenthetically, it may be remarked how fascinating for anyone Indeed, a few months ago we should have hesitated as to the wisdom with a lively imagination the evolution of these symbols must have of attempting to illustrate the equipment in this way. But fortunately been. There has been nothing, we surmise, like it since the electrical at the beginning of this year it once more became possible for us to symbols were first hammered out by someone, or a group of in return to the use of art paper for our editorial pages and the ex dividuals whose name, or names, are long since forgotten. It would cellent quality we are now able to use ensures that as little is lost in mean compressing into a few weeks, or months, of thought, and reproduction as is humanly possible. argument, an operation which presumably occupied centuries in An interesting point is that after experimenting with testing such a process as the gradual evolution of the letters to symbolize simultaneously the whole of the structure in a wing it was decided language, springing from the first crude drawings of animals and to revert to the earlier practice of the shot-bag test and check the household objects produced by cave men and growing into conven strength components, such as ribs, spars, joints and skin attachments tionalized symbols. in separate detailed tests. This naturally simplified the main wing Without trying to peer too closely into the minds of MR . HODGSON test by greatly reducing the number of attachments and fitting and his collaborators and imagine how they arrived at their con them only to spars and similar strong points. clusions, they are certainly to be congratulated on their co-operative One of the chief features of the new technique is that it makes effort and the results it has brought. possible the testing of complete-span specimens in one operation in a period of time which would otherwise be quite out of the question. Incidentally, this appears to be a matter in which Great Britain
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Apr 1, 1946
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