WIG Craft and Ekranoplan

Liang Yun · Alan Bliault · Johnny Doo

WIG Craft and Ekranoplan

Ground Effect Craft Technology

123

Liang YunMarine Design and Research Institute

of China (MARIC)1688 Xizhang Nan Road200011 ShanghaiPeople’s Republic of Chinaliangyunb@yahoo.com

Johnny DooTeledyne Continental Motors2039 Broad StreetP.O. Box 90Mobile, AL 36601USAdsn99@aol.com

Alan BliaultA/S Norske Shell4098 TanangerNorwayalan.bliault@shell.com

ISBN 978-1-4419-0041-8 e-ISBN 978-1-4419-0042-5DOI 10.1007/978-1-4419-0042-5Springer New York Dordrecht Heidelberg London

Library of Congress Control Number: 2009937415

© Springer Science+Business Media, LLC 2010All rights reserved. This work may not be translated or copied in whole or in part without the writtenpermission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York,NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use inconnection with any form of information storage and retrieval, electronic adaptation, computer software,or by similar or dissimilar methodology now known or hereafter developed is forbidden.The use in this publication of trade names, trademarks, service marks, and similar terms, even if they arenot identified as such, is not to be taken as an expression of opinion as to whether or not they are subjectto proprietary rights.

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Springer is part of Springer Science+Business Media (www.springer.com)

Preface

In the last half-century, high-speed water transportation has developed rapidly.Novel high-performance marine vehicles, such as the air cushion vehicle (ACV),surface effect ship (SES), high-speed monohull craft (MHC), catamaran (CAT),hydrofoil craft (HYC), wave-piercing craft (WPC) and small water area twinhull craft (SWATH) have all developed as concepts, achieving varying degrees ofcommercial and military success.

Prototype ACV and SES have achieved speeds of 100 knots in flat calm condi-tions; however, the normal cruising speed for commercial operations has remainedaround 35–50 knots. This is partly due to increased drag in an average coastal sea-way where such craft operate services and partly due to limitations of the propulsionsystems for such craft. Water jets and water propellers face limitations due to cav-itation at high speed, for example. SWATH are designed for reduced motions in aseaway, but the hull form is not a low drag form suitable for high-speed operation.

So that seems to lead to a problem – maintain water contact and either waterpropulsion systems run out of power or craft motions and speed loss are a problemin higher seastates. The only way to higher speed would appear to be to disconnectcompletely from the water surface.

You, the reader, might respond with a question about racing hydroplanes, whichmanage speeds of above 200 kph. Yes, true, but the power-to-weight ratio isextremely high on such racing machines and not economic if translated into a usefulcommercial vessel.

Disconnection of the craft from the water is indeed a logical step, but it has itsconsequences. The craft must be propelled by air and it will have to be supported byair as well. A low flying aircraft? In some ways – yes – but with a difference. Whenan airplane flies very close to the ground a much higher pressure builds up under thewings – ground effect. Some early hovercraft were configured to capture air as theymoved forward – captured air bubble craft.

Combine ground effect with a geometry specifically designed to enhance theeffect and you have a craft that might be able to achieve much higher cruising speed.Flying above waves, its motions might also be much reduced. This idea gave birthto the wing-in-ground effect (WIG) craft.

The original type of WIG can be traced from at the beginning of last century.Actually, in 1903, the Wright Brothers flew their first airplane over relatively long

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distances in the surface effect zone. Engineer Kaario of Finland started tests ofcraft lifted by ground effect in the middle of 1930s. However, due to limitationsin the efficiency of structural materials and available engine power, the WIG wasnot developed further until the beginning of the 1960s.

These were ideas that excited Alexeev in Russia in the 1960s and 1970s after hisinstitute had developed several series of hydrofoil designs. Alexeev and his teamof Russian pioneers in this new vehicle technology were interested in very highspeeds, and their programme was developed directly from hydrofoil research. Thecraft were christened “Ekranoplan”. Parallel efforts on prototype craft and theoret-ical analysis gradually built experience and understanding through the 1970s and1980s leading to the first military service craft based in the Caspian Sea. This wasa truly outstanding technological achievement delivered through visionary supportfrom the Russian Navy.

In Germany, also in the 1970s, research and prototype craft aimed at using groundeffect was also carried out. Rather than the large military budget available in Russia,the German programmes were funded privately and later with low level support fromgovernment. This work led to ground effect craft suitable for high-speed coastalpatrol, though in limited sea conditions.

At the beginning of 1970s, Russian engineers Bartini and R.Y. Alexeev inventedpower-assisted lift arrangements for WIG craft by mounting jet engines in front ofthe main wing to feed engine exhaust air into the air channel under the wing tocreate the so-called power-augmented ram wing-in-ground effect craft (PARWIG).This augmented lift improved the take-off and landing performance by reducingtake-off speed and distance.

The full story of Alexeev’s craft is outlined in Chapter 2 together with otherdevelopments from around the world. The technical achievements were highly sig-nificant, and it is a pity that the economic situation in Russia through the 1990s wassuch that the programme had to be stopped. It may be some time before we seemachines to equal the KM and Spasatel.

In recent years, researchers in China and Russia have mixed air cushion tech-nology into the WIG to create the dynamic air cushion craft (DACC) and dynamicair cushion wing-in-ground effect craft (DACWIG) to produce craft with amphibi-ous capability and much higher transport efficiency at medium cruise speeds in therange 150–250 kph.

Since a WIG has several operational modes (floating hull, cushion and plan-ing, and air-borne modes), the craft design is rather more complex than aircraft orother marine craft. A WIG normally just transits through all the modes except flyingin ground effect, but unfortunately the drag forces and motions are the greatest atspeeds below take-off, so effective design for the conditions met during the take-offand landing runs is essential to a successful WIG design. The challenges are notover though – quasi-static and dynamic stability of a WIG when flying is stronglyinfluenced by both the flying height and the craft pitch angle.

Research into these areas is at an early stage and much more knowledge in thedifferent areas is needed. In this book, we give an outline of the knowledge as it

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exists right now. This provides a starting point, though readers are encouraged toseek out further sources for themselves!

Some accidents have occurred on full-scale WIG craft, so that there is someuncertainty as to the safety of WIG for potential operators at present. This is beingaddressed by a technical committee of the International Maritime Organisation(IMO) who have published a safety code in the form of guidelines for WIG in 2003.

The technology is indeed still somewhat experimental and needs a build-up ofoperational experience, even if it is at relatively small scale, in order to developconfidence for the commercial industry to gain enthusiasm for this new form oftransportation. The IMO guidelines should help a lot in this respect, but practicaloperations, perhaps following the example of the many SR.N6 hovercraft trials oper-ations and expedition journeys in the 1960s and 1970s, will be needed to prove theircapability and value to society.

On an international basis, the WIG craft is now recognised basically as a high-speed marine vehicle and will be certified as such, rather than being certified byaerospace authorities. This has significant cost and operational advantages thatshould assist in the craft’s commercialisation.

WIG are based upon a combination of aircraft and marine technology while beingdifferent from either. WIG operate both on water and in air as well as on the edge ofboth media. A WIG is neither an airplane nor watercraft as such. It is rather differ-ent either from airplane industry (sophisticated lightweight structures, high powerintensity, automated, heavy certification requirements, expensive construction etc.)or from watercraft (experience based design, relatively heavy structure, robust, lowcost, etc.). The WIG borrows from both technologies to achieve a high speed andlightweight, yet low-cost marine vehicle.

Our book begins with a general review of ground effect technology and a histor-ical review to give a background to the main body of the text covering the theory,as well as a design approach for WIG. This is the first major text on this subjectoutside Russia, so we hope to reach a worldwide audience and encourage interest inthis technology in between the marine and aerospace worlds!

There are this Preface, 13 chapters and Backmatter in the book. We intro-duce WIG craft concepts and background development in Chapters 1 and 2. FromChapters 3, 4, 5, 6, 7, 8 and 9, the book describes trim and longitudinal force bal-ance, static hovering performance, aerodynamic characteristics, stability, drag andpowering performance, seakeeping quality and manoeuvrability, and model exper-imental investigations. The materials and structures, power plant selection, and liftand propulsion system selection are introduced in Chapters 10, 11 and 12. In thesechapters, the issues related to WIG design are considered as a derivation from air-craft or marine design rather than giving a detailed treatise. In Chapter 13, a generalapproach to WIG concept specification and design is described.

The Postscript discusses prospects for the future and a series of technical issuesconcerned with the development of WIG that face researchers and engineers in thisarea at present. There is so much to work on at present. The WIG principle canbe applied to a wide envelope of operational speed and environmental conditions,

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leading to craft as different as gliders and jet airliners in the aircraft world. In addi-tion, if long distance transportation is to become reality, WIG will need a new formof “traffic lane” agreed at international level and documented on charts. Significantopportunities await us!

A comprehensive listing of references is included at the end of the book, clas-sified by chapter. These should be useful to the reader to provide more detailedinformation and support for the analysis and design.

The authors aim with this book to provide a useful reference for engineers,technicians, teachers and university students (both undergraduate and postgradu-ate), involved in the marine engineering world who are interested in WIG research,design, construction and operation.

Since the WIG is a novel technology and still in its initial development, the pre-sentation of some of the theory should be considered as statement of current state of(limited) art, so readers should take care to check for themselves the validity of thetheories presented here. The authors will be pleased to have comments and feedbackfrom readers.

Shanghai, PR China L. YunTananger, Norway A. BliaultMobile, Alabama J. DooMay 2009

Acknowledgements

The authors would like to express their sincere thanks to the leadership and col-leagues of the Marine Design and Research Institute of China (MARIC) and HPMVDesign Subcommittee of CSNAME, including Prof. Xing Wen Hua, Prof. LiangQi Kang (Managing Director, MARIC), Mr. Wang Gao Zhong (Deputy ManagingDirector of MARIC and also Former Chief Designer of WIG type SWAN), Prof.Peng, Gui-Hua (Director of HPMV Division, MARIC), Prof. Xie, You-Non (DeputyChief Designer of “SWAN”), Mr. Wu Cheng Jie, (Principal Designer of SWAN),Mr. Hu, An-Ding (Chief Designer of WIG “750”, MARIC) and Mr. Li, Ka-Xi(Chief Designer of WIG “XTW”, CSSRC), for their help and using their papersand research during the writing of this book.

We also wish to thank the following for material contributions and for permis-sion to use illustrations and photos: Johnny Doo (SSAC), Edwin van Opstal (SETechnology), Boeing Aircraft Company, Flightship Ground Effect Pty Ltd, FischerFlugmechanik/AFD Airfoil Development and Bob Windt (Universal Hovercraft).

Finally we wish to thank our peer review group who provided most valuablefeedback on the content and presentation of the book.

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Contents

1 Wings in Ground Effect . . . . . . . . . . . . . . . . . . . . . . . . 1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Marine Transport and WIG Development . . . . . . . . . . . . . . . 2Alternative Technologies . . . . . . . . . . . . . . . . . . . . . . . . 3

The Hydrofoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4The SES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4The Hovercraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Ground Effect for Higher Service Speed . . . . . . . . . . . . . . . . 6Some WIG Technical Terms . . . . . . . . . . . . . . . . . . . . . . 7

Ground Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Dynamic Air Cushion . . . . . . . . . . . . . . . . . . . . . . . . 8Static Air Cushion . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Basic Principles of Ground Effect . . . . . . . . . . . . . . . . . . . 9Types of WIG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Classic WIG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16PARWIG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

PARWIG Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 22PARWIG Limitations . . . . . . . . . . . . . . . . . . . . . . . . 22Military Applications . . . . . . . . . . . . . . . . . . . . . . . . 23Civil Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Dynamic Air Cushion Craft (DACC) . . . . . . . . . . . . . . . . . 25DACC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 27DACC Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 27Dynamic Air Cushion Wing-in-Ground Effect Craft (DACWIG) . . . 27DACWIG Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . 29DACWIG Applications . . . . . . . . . . . . . . . . . . . . . . . . . 32

2 WIG Craft Development . . . . . . . . . . . . . . . . . . . . . . . 33Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Russian Ekranoplan Development . . . . . . . . . . . . . . . . . . . 33

KM or “Caspian Sea Monster” . . . . . . . . . . . . . . . . . . . 42UT-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Orlyonok and Lun . . . . . . . . . . . . . . . . . . . . . . . . . . 45

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Orlyonok’s Accident . . . . . . . . . . . . . . . . . . . . . . . . . . 47The Development of Lun . . . . . . . . . . . . . . . . . . . . . . . . 51Key to Fig. 2.20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Second-Generation WIG . . . . . . . . . . . . . . . . . . . . . . . 54Design Studies for Large Commercial Ekranoplan in Russia . . . . 57Volga-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Recent Small Craft Designs . . . . . . . . . . . . . . . . . . . . . . 60Ivolga . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60Amphistar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Technical Data Summary for Russian WIG Craft . . . . . . . . . . . 63WIG Development in China . . . . . . . . . . . . . . . . . . . . . . 65

CSSRC PARWIG Craft . . . . . . . . . . . . . . . . . . . . . . . 67CASTD PARWIG . . . . . . . . . . . . . . . . . . . . . . . . . . 67DACWIG Craft Developed by MARIC . . . . . . . . . . . . . . . 70

The Conversion of “SWAN” . . . . . . . . . . . . . . . . . . . . . . 75WIG Developments in Germany . . . . . . . . . . . . . . . . . . . . 77

Tandem Airfoil Flairboats (TAF) . . . . . . . . . . . . . . . . . . 77Lippisch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Hoverwing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82WIG in the United States . . . . . . . . . . . . . . . . . . . . . . . . 85WIG in Australia . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Sea Wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Radacraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Flightship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Concluding Observations . . . . . . . . . . . . . . . . . . . . . . . . 93

3 Longitudinal Force Balance and Trim . . . . . . . . . . . . . . . . 95Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Operational Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Running Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98Centres of Effort and Their Estimation . . . . . . . . . . . . . . . . . 102

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102Longitudinal Centres of Forces Acting on WIG Craft . . . . . . . . . 103

Centre of Buoyancy (CB) . . . . . . . . . . . . . . . . . . . . . . 103Centre of Hydrodynamic Force Acting on Hull and Side Buoys . . 103Centre of Static Air Cushion Pressure (CP) . . . . . . . . . . . . . 104Centre of Aerodynamic Lift of a Single Wing Beyond the GEZ . . 104Centre of Lift of WIG Main Wing with Bow Thrustersin Ground Effect Zone . . . . . . . . . . . . . . . . . . . . . . . . 104Centre of Lift of a Whole WIG Craft Operating in GEZ . . . . . . 106

Influence of Control Mechanisms on Craft Aerodynamic Centres . . . 106Longitudinal Force Balance . . . . . . . . . . . . . . . . . . . . . . 109

Condition for Normal Operation of a WIG in VariousOperation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . 109Inherent Force-Balance Method . . . . . . . . . . . . . . . . . . . 111

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Controllable Equilibrium Method . . . . . . . . . . . . . . . . . . 112Handling of WIG During Take-Off . . . . . . . . . . . . . . . . . . . 114

4 Hovering and Slow-Speed Performance . . . . . . . . . . . . . . . 117Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117Hovering Performance Requirements . . . . . . . . . . . . . . . . . 118

Manoeuvring and Landing . . . . . . . . . . . . . . . . . . . . . . 118Low-Speed Operations . . . . . . . . . . . . . . . . . . . . . . . . 118Hump Speed Transit and Take-Off into GEZ . . . . . . . . . . . . 119Seakeeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

PARWIG Theory from the 1970s . . . . . . . . . . . . . . . . . . . . 120Static Hovering Performance of DACWIG and DACC . . . . . . . . 125

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125Configuration of a DACC or DACWIG . . . . . . . . . . . . . . . 126Static Hovering Performance of DACC and DACWIG . . . . . . . 127

Measures for Improving Slow-Speed Performance . . . . . . . . . . 138Inflatable Air Bag . . . . . . . . . . . . . . . . . . . . . . . . . . 141Skirt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142Laminar Flow Coating on the Bottoms of Hull and Side Buoys . . 142Hard Landing Pads . . . . . . . . . . . . . . . . . . . . . . . . . . 144

5 Aerodynamics in steady Flight . . . . . . . . . . . . . . . . . . . . 147Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147Airfoil Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . 148An Experimental Investigation of Airfoil Aerodynamics . . . . . . . 153

Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153Basic Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154Model Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175Drag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177Lift–Drag Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 177Pitching Moment . . . . . . . . . . . . . . . . . . . . . . . . . . . 178Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

WIG Aerodynamic Characteristics . . . . . . . . . . . . . . . . . . . 179Factors Influencing WIG Aerodynamic Characteristics . . . . . . . . 183

Bow Thruster with Guide Vanes or Jet Nozzle . . . . . . . . . . . 183Special Main-Wing Profile . . . . . . . . . . . . . . . . . . . . . . 184Aspect Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186Other Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

6 Longitudinal and Transverse Stability . . . . . . . . . . . . . . . . 189Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189Forces and Moments . . . . . . . . . . . . . . . . . . . . . . . . . . 189

Pitching Centres . . . . . . . . . . . . . . . . . . . . . . . . . . . 190Pitch Stability Design Criteria . . . . . . . . . . . . . . . . . . . . 191Height Stability Design Criteria . . . . . . . . . . . . . . . . . . . 191

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Main-Wing Airfoil and Geometry . . . . . . . . . . . . . . . . . . 192Influence of Flaps . . . . . . . . . . . . . . . . . . . . . . . . . . 192Tailplane and Elevators . . . . . . . . . . . . . . . . . . . . . . . 193Centre of Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . 193Influence of Ground Effect on Equilibrium . . . . . . . . . . . . . 194Influence of Bow Thrusters with Jet Nozzle or Guide Vanes . . . . 194Automatic Control Systems . . . . . . . . . . . . . . . . . . . . . 195

Stability Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195Static Longitudinal Stability in and Beyond the GEZ . . . . . . . . . 197

Static Longitudinal Stability of an Aircraft and a WIGOperating Beyond the GEZ . . . . . . . . . . . . . . . . . . . . . 198Basic Stability Equation . . . . . . . . . . . . . . . . . . . . . . . 199Wing Pitching Centre . . . . . . . . . . . . . . . . . . . . . . . . 200Pitching Pitching Centre . . . . . . . . . . . . . . . . . . . . . . . 201Flying Height Pitching Centre . . . . . . . . . . . . . . . . . . . . 203Estimation of Balance Centres . . . . . . . . . . . . . . . . . . . . 204

Static Longitudinal Stability Criteria . . . . . . . . . . . . . . . . . . 206Requirements for Positive Static Longitudinal Stability . . . . . . . 207

Static Transverse Stability of DACWIG in Steady Flight . . . . . . . 210WIG Operating in Weak GEZ . . . . . . . . . . . . . . . . . . . . 213Transverse Stability Criteria . . . . . . . . . . . . . . . . . . . . . 215Transverse Stability at Slow Speed . . . . . . . . . . . . . . . . . 216Transverse Stability During Turning . . . . . . . . . . . . . . . . . 216PARWIG Transverse Stability . . . . . . . . . . . . . . . . . . . . 217

Dynamic Longitudinal Stability over Calm Water . . . . . . . . . . . 217Basic Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 218Basic Motion Equations . . . . . . . . . . . . . . . . . . . . . . . 218

Transient Stability During Transition Phases . . . . . . . . . . . . . 222

7 Calm Water Drag and Power . . . . . . . . . . . . . . . . . . . . . 225Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225WIG Drag Components . . . . . . . . . . . . . . . . . . . . . . . . 230WIG Drag Before Take-Off . . . . . . . . . . . . . . . . . . . . . . 231

Hump Drag and Its Minimisation . . . . . . . . . . . . . . . . . . 231Estimation of the Craft Drag Before Take-Off . . . . . . . . . . . 234

WIG Drag After Take-Off . . . . . . . . . . . . . . . . . . . . . . . 239Drag of WIG After Take-Off . . . . . . . . . . . . . . . . . . . . 239

Powering Estimation for WIG . . . . . . . . . . . . . . . . . . . . . 243Performance Based on Wind-Tunnel Test Results of Modelwith Bow Thrusters in Operation . . . . . . . . . . . . . . . . . . 244Estimation of WIG Total Drag . . . . . . . . . . . . . . . . . . . . 245Drag Prediction by Correlation with Hydrodynamic ModelTest Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

Influences on Drag and Powering Over Calm Water . . . . . . . . . . 249Hull-Borne Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 250Transit Through Main Hump Speed (Fn = 2–4) . . . . . . . . . . 250

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During Take-Off (Fn = 4.0–8.0) . . . . . . . . . . . . . . . . . . . 250Flying Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

8 Seakeeping and Manoeuvrability . . . . . . . . . . . . . . . . . . 255Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255Differential Equation of WIG Motion in Waves . . . . . . . . . . . . 256

Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . 256Basic Longitudinal Differential Equations of DACWIGMotion in Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Seakeeping Model Tests . . . . . . . . . . . . . . . . . . . . . . . . 259Manoeuvrability and Controllability . . . . . . . . . . . . . . . . . . 267WIG Control in Flight . . . . . . . . . . . . . . . . . . . . . . . . . 268

The Influence of a Wind Gust on the Running Trim of WIGin Steady Flight . . . . . . . . . . . . . . . . . . . . . . . . . . . 270Nonlinear Analysis of WIG Motion . . . . . . . . . . . . . . . . . 271Special Cases of Craft Motion . . . . . . . . . . . . . . . . . . . . 273Manoeuvring in Hull-Borne Mode . . . . . . . . . . . . . . . . . 275

Take-Off Handling in Waves . . . . . . . . . . . . . . . . . . . . . . 275Turning Performance . . . . . . . . . . . . . . . . . . . . . . . . . . 276Operation of WIG Craft in Higher GEZ . . . . . . . . . . . . . . . . 280

9 Model Tests and Aero-hydrodynamic Simulation . . . . . . . . . . 283Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283Experimental Methodology . . . . . . . . . . . . . . . . . . . . . . 284

Static Hovering Experiments on a Rigid Ground Plane . . . . . . . 284Model Tests in a Towing Tank . . . . . . . . . . . . . . . . . . . . 284Model Experiments in a Wind Tunnel . . . . . . . . . . . . . . . . 285Radio-controlled Model Tests on Open Water and CatapultModel Testing Over Ground . . . . . . . . . . . . . . . . . . . . . 285

WIG Model Scaling Rules . . . . . . . . . . . . . . . . . . . . . . . 286Scaling Parameters for WIG . . . . . . . . . . . . . . . . . . . . . . 286

Reynold’s Number . . . . . . . . . . . . . . . . . . . . . . . . . . 286Euler Number (Hq) and Relation to Cushion Pressure Ratio . . . . 294Wind-Tunnel Testing . . . . . . . . . . . . . . . . . . . . . . . . . 294Bow Thruster or Lift Fan Non-dimensional Characteristicsof DACC and DACWIG . . . . . . . . . . . . . . . . . . . . . . . 297Froude Number, Fn . . . . . . . . . . . . . . . . . . . . . . . . . 299Weber Number, We . . . . . . . . . . . . . . . . . . . . . . . . . 299Other Scaling Terms for Towing Tank Test Models . . . . . . . . . 300Structural Simulation . . . . . . . . . . . . . . . . . . . . . . . . 301

Scaling Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301Model Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 302

10 Structural Design and Materials . . . . . . . . . . . . . . . . . . . 307Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

Waterborne and Pre-take-off Loads . . . . . . . . . . . . . . . . . 310

xvi Contents

Take-Off and Landing Loads . . . . . . . . . . . . . . . . . . . . 311Ground-Manoeuvring Loads . . . . . . . . . . . . . . . . . . . . . 312Flight Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313Impact and Handling Loads . . . . . . . . . . . . . . . . . . . . . 314Design Approach . . . . . . . . . . . . . . . . . . . . . . . . . . 315

Metallic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 316Composite Materials . . . . . . . . . . . . . . . . . . . . . . . . . . 318

Sandwich Construction . . . . . . . . . . . . . . . . . . . . . . . 320Fatigue, Damage Tolerance and Fail-Safe . . . . . . . . . . . . . . . 323WIG Structural Design Concepts and Considerations . . . . . . . . . 324

Basic Design Considerations . . . . . . . . . . . . . . . . . . . . 324

11 Power plant and Transmission . . . . . . . . . . . . . . . . . . . . 337Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337WIG Power Plant Type Selection . . . . . . . . . . . . . . . . . . . 338Internal Combustion Engines . . . . . . . . . . . . . . . . . . . . . . 339Turbofan/Turboshaft/Turboprop Engines . . . . . . . . . . . . . . . 341WIG Application Special Requirements . . . . . . . . . . . . . . . . 345

Marinisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345Altitude Operations . . . . . . . . . . . . . . . . . . . . . . . . . 346

Power Plant Installation Design . . . . . . . . . . . . . . . . . . . . 347Pylon/Nacelle Installation . . . . . . . . . . . . . . . . . . . . . . 347

Engine and System Cooling . . . . . . . . . . . . . . . . . . . . . . 348Internal Systems Installation . . . . . . . . . . . . . . . . . . . . . 348Water Spray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349Engine and System Cooling . . . . . . . . . . . . . . . . . . . . . 349Ice Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351

Transmission Systems . . . . . . . . . . . . . . . . . . . . . . . . . 351Drive Shaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

12 Lift and Propulsion Systems . . . . . . . . . . . . . . . . . . . . . 355Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355Power-Augmented Lift . . . . . . . . . . . . . . . . . . . . . . . . . 356Independent Lift Systems . . . . . . . . . . . . . . . . . . . . . . . 359Propulsion Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 361

Propeller and Ducted Fan Characteristics . . . . . . . . . . . . . . 363Turbofan System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367Integrated Lift/Propulsion System . . . . . . . . . . . . . . . . . . . 369Propulsor Selection and Design . . . . . . . . . . . . . . . . . . . . 372

13 Concept Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373General WIG Application Issues . . . . . . . . . . . . . . . . . . . . 376

Technical Factors . . . . . . . . . . . . . . . . . . . . . . . . . . 377Operational Factors . . . . . . . . . . . . . . . . . . . . . . . . . 379

Contents xvii

WIG Subtypes and Their Application . . . . . . . . . . . . . . . . . 381WIG Preliminary Design . . . . . . . . . . . . . . . . . . . . . . . . 383Design Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384Functional Specification for a WIG . . . . . . . . . . . . . . . . . . 385Design Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 388Safety Codes for WIG Craft . . . . . . . . . . . . . . . . . . . . . . 393

Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393Supplementary Safety Criteria for DACWIG . . . . . . . . . . . . 394

Setting Up a Preliminary Configuration . . . . . . . . . . . . . . . . 396Procedure for Overall Preliminary Design . . . . . . . . . . . . . . . 414Determination of WIG Aerodynamic and HydrodynamicCharacteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414WIG Detailed Design . . . . . . . . . . . . . . . . . . . . . . . . . . 415

Postscript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

References and Resources . . . . . . . . . . . . . . . . . . . . . . . . . . 433

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441