BASIC HELICOPTER AERODYNAMICS

BASIC HELICOPTER AERODYNAMICS 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com Aerospace Series List Basic Helicopter Aerodynamics, Third Edition Seddon and Newman August 2011 AdvancedControl ofAircraft, Rockets and Spacecraft Tewari July 2011 Cooperative Path Planning of Unmanned Aerial Vehicles Tsourdos et al. November 2010 Principles of Flight for Pilots Swatton October 2010 Air Travel and Health: A Systems Perspective Seabridge et al. September 2010 Design and Analysis of Composite Structures: With applications to Aerospace Structures Kassapoglou September 2010 Unmanned Aircraft Systems: UAVS Design, Development and Deployment Austin April 2010 Introduction to Antenna Placement and Installations Macnamara April 2010 Principles of Flight Simulation Allerton October 2009 Aircraft Fuel Systems Langton et al. May 2009 The Global Airline Industry Belobaba April 2009 Computational Modelling and Simulation of Aircraft and the Environment: Volume 1 – Platform Kinematics and Synthetic Environment Diston April 2009 Handbook of Space Technology Ley, Wittmann and Hallmann April 2009 Aircraft Performance Theory and Practice for Pilots Swatton August 2008 Surrogate Modelling in Engineering Design: A Practical Guide Forrester, Sobester and Keane August 2008 Aircraft Systems, Third Edition Moir and Seabridge March 2008 Introduction to Aircraft Aeroelasticity And Loads Wright and Cooper December 2007 Stability and Control of Aircraft Systems Langton September 2006 Military Avionics Systems Moir and Seabridge February 2006 Design and Development of Aircraft Systems Moir and Seabridge June 2004 Aircraft Loading and Structural Layout Howe May 2004 Aircraft Display Systems Jukes December 2003 Civil Avionics Systems Moir and Seabridge December 2002 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com BASIC HELICOPTER AERODYNAMICS Third Edition John Seddon Formerly of the Ministry of Defence, UK Simon Newman Aeronautics and Astronautics, University of Southampton, UK 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com � 2011 John Wiley & Sons, Ltd Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com. The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Seddon, John M. Basic helicopter aerodynamics / John Seddon, Simon Newman. – 3rd ed. p. cm. Includes bibliographical references and index. ISBN 978-0-470-66501-5 (hardback) 1. Helicopters–Aerodynamics. I. Newman, Simon, 1947- II. Title. TL716.S43 2011 629.133’352–dc22 2011010960 A catalogue record for this book is available from the British Library. Print ISBN: 9780470665015 ePDF ISBN: 9781119994107 oBook ISBN: 9781119994114 ePub ISBN: 9781119972723 Mobi ISBN: 9781119972730 Set in 10/12pt Times by Thomson Digital, Noida, India 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com To Stella, for everything 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com Contents About the Authors xi Series Preface xiii Preface to First Edition xv Preface to Second Edition xvii Preface to Third Edition xix Notation xxiii Units xxvii Abbreviations xxix 1 Introduction 1 1.1 Looking Back 1 1.1.1 Early Years 1 1.1.2 First World War Era 3 1.1.3 Inter-war Years 3 1.1.4 Second World War Era 6 1.1.5 Post-war Years 7 1.1.6 The Helicopter from an Engineering Viewpoint 13 1.2 Book Presentation 22 Reference 22 2 Rotor in Vertical Flight: Momentum Theory and Wake Analysis 23 2.1 Momentum Theory for Hover 23 2.2 Non-dimensionalization 25 2.3 Figure of Merit 26 2.4 Axial Flight 29 2.5 Momentum Theory for Vertical Climb 29 2.6 Modelling the Streamtube 34 2.7 Descent 37 2.8 Wind Tunnel Test Results 45 2.9 Complete Induced-Velocity Curve 49 2.9.1 Basic Envelope 49 2.9.2 Autorotation 51 2.9.3 Ideal Autorotation 52 2.10 Summary Remarks on Momentum Theory 52 2.11 Complexity of Real Wake 53 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com 2.12 Wake Analysis Methods 55 2.13 Ground Effect 58 2.14 Brownout 60 References 61 3 Rotor in Vertical Flight: Blade Element Theory 63 3.1 Basic Method 63 3.2 Thrust Approximations 68 3.3 Non-uniform Inflow 70 3.3.1 Constant Downwash 71 3.4 Ideal Twist 71 3.5 Blade Mean Lift Coefficient 73 3.6 Power Approximations 74 3.7 Tip Loss 76 3.8 Example of Hover Characteristics 78 Reference 78 4 Rotor Mechanisms for Forward Flight 79 4.1 The Edgewise Rotor 79 4.2 Flapping Motion 85 4.3 Rotor Control 88 4.4 Equivalence of Flapping and Feathering 94 4.4.1 Blade Sailing 95 4.4.2 Lagging Motion 95 4.4.3 Coriolis Acceleration 95 4.4.4 Lag Frequency 98 4.4.5 Blade Flexibility 99 4.4.6 Ground Resonance 99 References 109 5 Rotor Aerodynamics in Forward Flight 111 5.1 Momentum Theory 111 5.2 Descending Forward Flight 115 5.3 Wake Analysis 120 5.3.1 Geometry of the Rotor Flow 120 5.4 Blade Element Theory 125 5.4.1 Factors Involved 125 5.4.2 Thrust 128 5.4.3 In-Plane H-force 130 5.4.4 Torque and Power 131 5.4.5 Flapping Coefficients 133 5.4.6 Typical Numerical Values 136 References 138 6 Aerodynamic Design 139 6.1 Introductory 139 6.2 Blade Section Design 139 6.3 Blade Tip Shapes 144 viii Contents 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com 6.3.1 Rectangular 144 6.3.2 Swept 144 6.3.3 Advanced Planforms 146 6.4 Tail Rotors 148 6.4.1 Propeller Moment 151 6.4.2 Precession – Yaw Agility 155 6.4.3 Calculation of Downwash 160 6.4.4 Yaw Acceleration 162 6.4.5 Example – Sea King 164 6.5 Parasite Drag 165 6.6 Rear Fuselage Upsweep 168 6.7 Higher Harmonic Control 172 6.8 Aerodynamic Design Process 173 References 177 7 Performance 179 7.1 Introduction 179 7.2 Hover and Vertical Flight 180 7.3 Forward Level Flight 183 7.4 Climb in Forward Flight 184 7.4.1 Optimum Speeds 186 7.5 Maximum Level Speed 187 7.6 Rotor Limits Envelope 187 7.7 Accurate Performance Prediction 188 7.8 AWorld Speed Record 189 7.9 Speculation on the Really Low-Drag Helicopter 191 7.10 An Exercise in High-Altitude Operation 193 7.11 Shipborne Operation 195 References 200 8 Trim, Stability and Control 201 8.1 Trim 201 8.2 Treatment of Stability and Control 204 8.3 Static Stability 205 8.3.1 Incidence Disturbance 206 8.3.2 Forward Speed Disturbance 207 8.3.3 Angular Velocity (Pitch or Roll Rate) Disturbance 207 8.3.4 Sideslip Disturbance 207 8.3.5 Yawing Disturbance 207 8.3.6 General Conclusion 207 8.4 Dynamic Stability 208 8.4.1 Analytical Process 208 8.4.2 Special Case of Hover 208 8.5 Hingeless Rotor 209 8.6 Control 209 8.7 Autostabilization 211 References 213 Contents ix 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com 9 A Personal Look at the Future 215 References 222 Appendix: Performance and Mission Calculation 223 A.1 Introduction 223 A.2 Glossary of Terms 224 A.3 Overall Aircraft 224 A.3.1 Main Rotor 225 A.3.2 Tail Rotor 227 A.3.3 Complete Aircraft 228 A.3.4 Example of Parameter Values 228 A.4 Calculation of Engine Fuel Consumption 229 A.5 Engine Limits 230 A.5.1 Maximum Continuous Power Rating 231 A.5.2 Take-Off or 1 Hour Power Rating 231 A.5.3 Maximum Contingency or 21/2 Minute Power Rating 231 A.5.4 Emergency or 1/2 Minute Power Rating 231 A.6 Calculation of the Performance of a Helicopter 231 A.6.1 Influence of Wind 236 A.7 Mission Analysis 237 A.7.1 Calculation Method 238 A.7.2 Atmospheric Parameters 238 A.7.3 Downwash Calculation 239 A.8 Helicopter Power 240 A.9 Fuel Flow 242 A.10 Mission Leg 242 A.11 Examples of Mission Calculations 244 A.12 Westland Lynx – Search and Rescue 245 A.12.1 Description of the Mission 245 A.12.2 Fuel Consumption 246 Index 249 x Contents 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com About the Authors The late John Seddon was a research scientist at the Royal Aircraft Establishment and then Director-General in the UK Ministry of Defence. He later became a consultant to Westland Helicopters. Simon Newman attended Grammar School in Farnborough near the site of the Royal Aircraft Establishment. He then read mathematics at the University of Southampton, graduating in 1970. Continuing the aircraft theme, he then began a career in helicopter aerodynamics, dynamics and design for the next 41 years. Starting at Westland Helicopters, at Yeovil, Somerset, in 1970 he worked in the Aerodynamics Research Department on rotors systems, performance and aeromechanics. After a year back at Southampton in 1974, where he obtained an MSc in Aeronautics, he returned to Yeovil to work in the Aerodynamics and Dynamics Departments on rotor aerodynamics, blade behaviour and shipborne operations. He was in the Technical Office during the Falklands War, contributing to the technical backup. In 1985 he returned to Southampton as a member of academic staff, reaching the grade of Reader in 2007. His research interests have concentrated on shipborne operations, blade sailing in particular, for which he obtained his doctorate in 1995. Other research has focused on the vortex ring state and the tumble behaviour of microlight aircraft. He has several hobbies, principally photogra- phy and golf. Apart from his academic duties, he is also an Esquire Bedell of the University, carrying the mace at graduation ceremonies. 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com Series Preface The field of aerospace is wide ranging and multi-disciplinary, covering a large variety of products, disciplines and domains, not merely in engineering but in many related supporting activities. These combine to enable the aerospace industry to produce exciting and technolog- ically advanced products. The wealth of knowledge and experience that has been gained by expert practitioners in thevarious aerospace fields needs to be passed onto othersworking in the industry, including those just entering from University. The Aerospace Series aims to be practical and topical series of books aimed at engineering professionals, operators, users and allied professions such as commercial and legal executives in the aerospace industry. The range of topics is intended to be wide ranging, covering design and development, manufacture, operation and support of aircraft as well as topics such as infrastructure operations and developments in research and technology. The intention is to provide a source of relevant information that will be of interest and benefit to all those people working in aerospace. Helicopters are able to perform a wide range of roles that are not possible with conventional fixed wing aircraft, particularly due to their capability to hover, and to take-off and land vertically. There are a number of technical difficulties that have presented helicopter designers withmany challenges over the years, including the aerodynamics offlexible rotors that not only provide lift, but also enable the helicopter to move forward in the desired direction. This book, Basic Helicopter Aerodynamics, is the third edition of the original version that was written by the late John Seddon. SimonNewman hasmaintained the ethos of the first book, producing a further revision of this introductory text aimed at undergraduates and engineers new to the field that illustrates the fundamental features of rotor aerodynamics and helicopter design. Importantly, the book alsomaintains the balance of not delving into toomuch technical detail, whilst avoiding gross simplification of key important features and physical explana- tions. There is much to be commended in this latest expanded edition which contains a number of valuable additions to the material. Peter Belobaba, Jonathan Cooper, Roy Langton and Allan Seabridge 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com Preface to First Edition During the past decade and a half, several noteworthy textbooks have been published in the previously neglected field of helicopter aerodynamics, spurred no doubt by a growing acceptance world-wide of the importance of the helicopter in modern society. One may cite in this context Bramwell’s Helicopter Dynamics (1976), Johnson’s Helicopter Theory (1980) and Rotary Wing Aerodynamics (1984) by Stepniewski and Keys. The appearance now of another book on the subject requires some explanation, therefore. I have three specific reasons for writing it. The first reason is one of brevity. Bramwell’s book runs to 400 pages, that of Stepniewski and Keys to 600 and Johnson’s extremely comprehensive treatment to over 1000. The users I have principally inmind areUniversity or Polytechnic students taking a short course of lectures – say oneyear– in the subject,probablyas an ‘optional’ or ‘elective’ in thefinalundergraduateorearly post-graduate year. The object in that time is to provide themwith a grounding while hopefully stimulating an interestwhichmay carry them further in the subject at a later date. The amount of teaching material required for this purpose is only a fraction of that contained in the standard textbooksandamonographofaround150pages ismore than sufficient to containwhat isneeded and hopefully may be produced at a price not beyond the individual student’s pocket. My second reason, which links with the first, concerns the type of approach. This book does not aim at a comprehensive treatment but neither is it content to consign problems to the digital computer at the earliest opportunity. In between lies an analytical route to solutions, taken far enough to produce results of usable accuracy for many practical purposes, while at the same time providing a physical understanding of the phenomena involved, which rapid recourse to the computer often fails to do. It is this route that the book attempts to follow. The analytical approach is usually terminated when it is thought to have gone far enough to serve the stated purpose, the reader being left with a reference to one of the standard textbooks in case he should wish to pursue the topic further. The third reason is one of content. Despite the need for brevity, I have thought it worthwhile to include, in addition to treatments of the standard topics – momentum theory, blade element theory, basic performance, stability and control – a strong flavour of research and development activity (Chapter 6) and of forward-looking, if speculative, calculations (Chapter 7). Itmight be considered that these items are of such a transitory nature as not to be suitable for a textbook, but my criterion of stimulating the student’s interest is what has determined their inclusion. Certainly they have proved to be interesting in classroom presentation and there seems no reason why that should not be so for the written word. In addition to meeting the needs of students, to whom it is primarily addressed, the book should have an appeal as background material to short courses held in or on behalf of industry: such courses are increasing in popularity. Companies and research establishments may also find it useful for new entrants and for more established workers requiring a ‘refresher’ text. 无水印完整版本下载：www.n-ebook.com Doc uCo m P DF Tria l ww w.pd fwiz ard. com Reverting to thematter of brevity, the recent publicationHelicopter Aerodynamics by Prouty is a most admirable short exposition, well worth studying as an adjunct to any other textbook: however it shuns themathematics completely and thereforewill not suffice alone for the present purposes. Saunders’ Dynamics of Helicopter Flight is not greatly beyond the target length but as the title implies it is concerned more with flight dynamics than with aerodynamics and is adapted more to the needs of pilots than to those of engineering students already equipped with a general aerodynamic background. I have taken it as a starting point that my readers have a knowledge of the aerodynamics of lifting wings as they exist in fixed-wing aircraft. A helicopter rotor blade performs the same function as a lifting wing but in a very different environment; and to note the similarities on the one hand and the distinctions on the other can be a considerable fillip to the learner’s interest, one which I have tried to nurture by frequent references back to fixed-wing situations. This again is a somewhat non-standard approach. Substantial omissions from the book are not hard to find.A historical surveymight have been included in Chapter 1 but was thought not necessary despite its undoubted interest. To judge by the work effort it attracts, wake analysis (‘Vortex theory’) deserves a more extensive treatment than it gets (Chapters 2 and 5) but here it was necessary to refrain from opening a Pandora’s box of different approaches. Among topics which could have been included in Chapter 5 are autorotation in forward flight, pitch-flap coupling and blade flexibility but these were seen as marginally ‘second-line’ topics. The forward look in Chapter 6 might have contained a discussion of the potential of circulation control, the only systemwhich is capable of attacking all the three non-uniformities of rotor blade flow, chordwise, spanwise and azimuthal; but the subject is too big and too distinct from the main line of treatment. The reference to autostabilization in Chapter 8 is brief in the extreme but again the choice was between this and a much lengthier exposition in which aerodynamics would have been largely submerged beneath system mechanics and electronics. In compiling the book I have been greatly helped by discussions with Mr D.E.H. (‘Dave’) Balmford, Head of Advanced Engineering at Westland Helicopters, to whom my thanks are expressed. Other Westland staff members whose assistance I wish to acknowledge in specific contexts are Dr M.V. Lowson (now Professor of Aerospace Engineering at Bristol Univer- sity) for Section 7.10, Mr F.J. Perry for Section 6.6, Mr R.V. Smith for Section 7.11 and Mr B. Pitkin for Chapter 8. Naturally the standard textbooks, particularly those mentioned earlier, have been invaluable in places and I trust that this fact is duly recognized in the text and diagrams. Formal acknowledgement is made to Westland