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Aviation History
1926
1926 - 0119.PDF
February 25, 1926 Supplement to FLIGHT ENGINEERINGSECTION . Edited by C. M. POULSEN February 2'-, 1926 CONTENTS Aircraft Performance. By J. D. North, F.R.Ae..S. Metal Spars. By J. D. Haddon, B.Sc, A.F.R.Ae.S An Interesting Undercarriage Leg Stalled Flight and Control. By Frank T. Courtney In the Drawing Office: Stream-Line Struts. By Lt.-Col. J. D. Blyth Technical Literature PAGE 13 15 18 2n 21 OUR CONTRIBUTORS Mr. J. D. North will be too well known to our readers to require any introduction here. Perhaps he is best known for his work on all-metal, and more particularly all-steel, construction of aeroplanes, a form of construction in which the firm with which Mr. North is connected—Boulton and Paul, Ltd.—has specialised for several years. We regard ourselves as being extremely fortunate in having obtained from Mr. North the promise of a series of articles, the first of which appears in the present issue. For a start, Mr. North will deal, not with metal construction, but with the subject of performance, the reconsideration of which, in the light of the vortex theory and dimensional theory, is considered essential to the determination of optimum types of construction. Mr. J. D. Haddon, who has, we understand, been associated with several firms during their earlier work on metal construc- tion, contributes an article on the design of metal spars of the type built up from strip. The subject is one that is coming to the fore very much at the present time, and the example given should be of material assistance to those whose duty it will be during the next year or two to produce satisfactory spars of this type. Mr. Haddon also gives a few words of advice on the design of rollers, and illustrates his method by an example. Mr. F. T. Courtney is one of Great Britain's best known test pilots, and has flown a very large variety of machines. He holds some very pronounced views on the subject of control f-nd stalling (as on most other subjects), and, although the nrticle which he has contributed is not a technical one. we have thought ourselves justified in publishing it in THE AIRCRAFT ENGINEER, since this will give technical experts opportunity of replying. The article is of rather a contro- rsial character, and doubtless will call forth a lively 'respondence. ' In the Drawing Office " is a section which we propose to 'ote to time-saving " dodges," and the Editor will welcome tributions for this section. In this issue Col. Blyth gives iort cut to the calculation of areas and moments of inertia treamline struts. £:: AIRCRAFT PERFORMANCE. By J. D. North, F.R.Ae.S. There is no property of the aeroplane flying machine which arouses greater interest in all associated with its design, manufacture, or use, than what we have come to call '' performance." Performance, of course, is a very vague word. It is vague in the sense that the term manoeuvrability is vague, and the properties of manoeuvrability and per- formance merge into one another and overlap. If we consider manoeuvrability to mean the capacity of an aeroplane to take up a fresh position in space, we are bound to take into consideration its properties of movement in two of the six degrees of freedom, viz. :—its horizontal and vertical speed. More strictly, we should confine the question of performance to the study of a two-dimensional motion of the aeroplane in its plane of symmetry. If we accept this definition of performance, we can cover the whole question of taking off from rest, climbing and flying at various heights and throttle settings, and we can specify properties within these limitations which will serve to define the requirements of aerodynamic design, except in so far as they may be limited by extraneous considerations, such, for example, as the necessity for rapid angular motion about any axis, or arbitrary limitations of size, or arrangements from considerations of housing, accom- modation, or functional requirements such as view, gun power, etc. In examining the question of performance, it is difficult to find a real starting point. We might assume that the starting point was the user's specification ; in other words, that his specification will require the machine to carry a definite useful load, and to be capable of a certain performance (and we shall continue to use this word to mean linear motion in the plane of symmetry) for a given endurance. He will, in addition, require certain economic conditions to be satisfied. This, in fact, really begs the question, since the user's requirements, particularly in military matters, are based, not on some extraneous principles of economics, but on the inherent performance capacity of the aeroplane flying machine. It is, therefore, necessary for the user to know what can be obtained before he can accurately specify his requirements. This is more difficult since, even within the limits as to the meaning of performance laid down, there are an infinite variety of combinations of climb and speed at the disposal of the user. Thus, the grade or class of perform- ance may be interpreted as a rapid and sustained climb to great heights, as if a machine were being designed for taking the altitude record, or, alternatively, it may be interpreted as speed at ground level, as if the machine were intended for 110a
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