The Anatomy of the Airplane Darrol Stinton Past Senior Visiting Fellow
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The Anatomy of the Airplane Darrol Stinton Past Senior Visiting Fellow, Loughborough University of Technology, Leicestershire, UK Second Edition Co-published by: American Institute of Aeronautics and Astronautics, Inc. 1801 Alexander Bell Drive, Reston, VA 20191 and Blackwell Science Ltd, Osney Mead, Oxford, 0X2 OEL, UK American Institute of Aeronautics and Astronautics, Inc. 1801 Alexander Bell Drive, Reston, VA 20191 ISBN 1-56347-286-4 (softcover: alk. paper) Copyright 1966, 1985, 1998 by Darrol Stinton. THE AUTHOR Darrol Stinton MBE, PhD, CEng, FRAeS, FRINA, MIMechE, RAF(Retd) was born in New Zealand and grew up in England. He is a qualified test pilot and aeronautical engineer who worked in the design offices of the Blackburn and De Havilland aircraft companies before joining the RAF. His test flying spanned 35 years and more than 340 types of aircraft, first as an experimental test pilot at Farnborough; then 20 years as airworthiness certification test pilot for the UK Civil Aviation Authority on light airplanes and seaplanes, before turning freelance. He has lectured regularly at the Empire Test Pilots’ School, Loughborough University, the Royal Aeronautical Society (of which he is a Past Vice President), and the Royal Institution of Naval Architects. His company specializes in cross-fertilization between aircraft and marine craft design and operation. ALSO AVAILABLE The Design of the Airplane Darrol Stinton 0-632-01 877-1 Flying Qualities and Flight Testing of the Airplane Darrol Stinton 1-56347-274-0 ‘If anyone tries to tell you something about an aeroplane which is so damn complicated that you can’t understand it you can take it from me it’s all balls.’ R. J. Mitchell (1895—1937) Designer of the Supermarine Spitfire Preface to the First Edition One should never have too much reverence for ideas, no matter whose they are. Ideas are meant to be kicked around, stood upon their heads, and looked at backwards in mirrors. It is only in this way that they can grow up in the way that they should, without excessive self-importance. The ideas of one man are the food for thought of another. Perhaps Oliver Wendell Holmes had this in mind when he said something to the effect that: ‘A man's mind stretched by a new idea can never go back to its original dimensions’. And that is the reason for this book. The Anatomy of the Aeroplane was started in 1960 as a set of supplementary notes to the author’s annual lectures on Aero-Structures given at the Empire Test Pilots’ School, at Farnborough in Hampshire. The lectures were intended to give embryo test pilots an insight into the reasons for aircraft not being shaped in ways that fitted the often more elegant theories. In so doing the inherent capabilities and limitations of an aeroplane became more apparent. The capabilities and limitations were seen to be functions of specific requirements: those formalized statements of human needs that cause aircraft to be made as useful and as safe as possible within the ‘state-of-the-art’ at a given time. The seeming dichotomy of the two worlds of theory and practice — usually more apparent to the practical man than the academician — is resolved by looking at the development of an aircraft as a response to a set of requirements. The aim of the book is to show students of aeronautics how requirements affect the application of theories, causing aeroplanes to be twisted, bent, cambered and kinked, to end up without the flowing perfection of their original, idealized, forms. It is aimed in particular at students in developing countries who, the author has found, are bursting with the desire to learn and assert their own ideas, but who cannot yet gain the practice they require. To this end a number of specialized subjects are introduced and shown in relation to the end product of the finished aeroplane. In this way the student will be able to specialize later with some idea of where his own subject fits into the whole. The treatment of the subject is such that the reader should be able to reason for himself why every salient feature of any aeroplane is shaped as it is. In doing this the book will probably make some enemies among those who cherish a professional mystique behind which to hide. That does not matter, for the book will have served its purpose if only one student gets a better feel for his subject than he might otherwise have had. The word aeroplane is used throughout in preference to airplane, or the meaningless plane, for two reasons. The first is that it is a scholarly word applied to a particular order of a class of aircraft. The second is that it derives from two Greek words meaning, literally, airwandering. That is excellent, for the word touches in part upon the spirit of aeronautics and the impulse to wander in the air that made men want to fly in the first place. The Concise Oxford Dictionary describes an aeroplane as a ‘mechanically-driven heavier-than-air flying-machine’. Taking the definition further: the Glossary of Aeronautical Terms of the British Standards Institution defines an aeroplane as ‘a power-driven heavier-than-air aircraft with supporting surfaces fixed for flight’. The name includes landplanes, seaplanes (float-seaplanes and flying boats), and amphibians (float-amphibians and boat-amphibians). Unfortunately, precise definitions of this kind miss out the most beautiful of all winged machines, that comes nearer to wandering-in-the-air than any other: the sailplane. For the purposes of this book the definition will treat an aeroplane as a heavier-than-air flying-machine with fixed wings (i.e. wings that do not beat the air as a means of propulsion, although they may be moved fore and aft in flight) while avoiding any need to specify the means of propulsion. There is no great inconsistency in doing so, for the first aeroplanes grew from kites and gliders, and the sailplane is a highly refined glider. The evolution of powered aeroplanes is such that they outstrip the definition. Since sustained flight became a possibility, little more than half a century ago, the performance of the aeroplane has increased more than one hundred fold. Cruising speeds and heights, range and endurance, carrying capacity and weight (and complication) have all increased. In order to fly fast smaller wings are used to achieve optimum efficiency, but smaller wings bearing heavier loads require more space for take-off and landing, and space is at a premium. This has led, under pressure of military necessity, to the development of short and vertical take-off, STOL and VTOL aeroplanes. We may not like to recognize it, but most significant advances are brought about through military necessity. And now there are dreams of aeroplanes employing powered lift throughout the whole envelope of flight, for cruising as well as for take-off and landing. The scope of the book is broad. Essentially it is a physical textbook, written in five parts, with a number of additional appendices. These have been added in order to focus attention upon some specific areas of operation: supersonic transports, aero-buses, strike and reconnaissance aeroplanes of various kinds. As far as possible early project aeroplanes have been used as illustrations, for these show most clearly the first thoughts of designers, with little adulteration. Many of the aircraft shown are really in the form of feasibility studies — the stage before becoming a project, in which a particular way of doing a job is investigated to see if it is worth continuing with as a project. Mathematical statements are simple, amounting to little more than 1 + 1 = 2, or 3 = 6/2, and using symbols to say so. Although British symbols are used these are defined, and repeated where relevant, so that the foreign reader should have no difficulty in converting them to the standard symbols of his own country. Equations are, for the most part, unit-less —although the ft-lb-sec system is used where stated. The reason for avoiding units is that the ideas count more than quantitative results, which belong properly in a handbook of aircraft design. Some basic calculus symbols are used, but it is only necessary to know what is meant by Δx and dx when they appear. A significant departure from standard works on aerodynamics is that to explain the nature of aerodynamic phenomena and forces aeroplanes are considered in motion through the air, instead of the usual reverse. There is plenty of time for the reader to come round to the conservative point of view, of visualizing an aircraft somehow motionless in space, with air flowing past it. This view has been deliberately rejected, not only because aeroplanes do not fly that way, but because certain concepts — like circulation, and its effect upon aerodynamic forces — are more readily understandable if one goes straight to the point of trying to see what really happens to the air. Furthermore, stability and control (neither of which are easily mastered if one is not happy with textbook mathematics) become simpler when seen as the pilot sees them: as properties of a machine that, under his hands, seems to be alive as it moves through apparently living air. The author is indebted to a large number of people who, directly and indirectly, have either helped by providing material, or have helped with the play of ideas thrown up as the book was written. Among these are three test pilots: Wing Commander N. F. Harrison DSO, AFC, RAF, Don Wright, and Squadron Leader G. M. Morrison, RAF. Others are Ernest Stott, the artist: Squadron Leader J.