WIG Craft and Ekranoplan Liang Yun · Alan Bliault · Johnny Doo

WIG Craft and Ekranoplan

Ground Effect Craft Technology

123 Liang Yun Alan Bliault Marine Design and Research Institute A/S Norske Shell of China (MARIC) 4098 Tananger 1688 Xizhang Nan Road Norway 200011 Shanghai [email protected] People’s Republic of China [email protected]

Johnny Doo Teledyne Continental Motors 2039 Broad Street P.O. Box 90 Mobile, AL 36601 USA [email protected]

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

Library of Congress Control Number: 2009937415

© Springer Science+Business Media, LLC 2010 All rights reserved. This work may not be translated or copied in whole or in part without the written permission 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 in connection 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 are not identiﬁed as such, is not to be taken as an expression of opinion as to whether or not they are subject to 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 twin hull craft (SWATH) have all developed as concepts, achieving varying degrees of commercial and military success. Prototype ACV and SES have achieved speeds of 100 knots in flat calm conditions; however, the normal cruising speed for commercial operations has remained around 35–50 knots. This is partly due to increased drag in an average coastal seaway where such craft operate services and partly due to limitations of the propulsion systems 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 a seaway, 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 water propulsion systems run out of power or craft motions and speed loss are a problem in higher seastates. The only way to higher speed would appear to be to disconnect completely from the water surface. You, the reader, might respond with a question about racing hydroplanes, which manage speeds of above 200 kph. Yes, true, but the power-to-weight ratio is extremely high on such racing machines and not economic if translated into a useful commercial vessel. Disconnection of the craft from the water is indeed a logical step, but it has its consequences. The craft must be propelled by air and it will have to be supported by air as well. A low flying aircraft? In some ways – yes – but with a difference. When an airplane flies very close to the ground a much higher pressure builds up under the wings – ground effect. Some early hovercraft were configured to capture air as they moved forward – captured air bubble craft. Combine ground effect with a geometry specifically designed to enhance the effect 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 birth to 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

v vi Preface distances in the surface effect zone. Engineer Kaario of Finland started tests of craft lifted by ground effect in the middle of 1930s. However, due to limitations in the efficiency of structural materials and available engine power, the WIG was not developed further until the beginning of the 1960s. These were ideas that excited Alexeev in Russia in the 1960s and 1970s after his institute had developed several series of hydrofoil designs. Alexeev and his team of Russian pioneers in this new vehicle technology were interested in very high speeds, and their programme was developed directly from hydrofoil research. The craft were christened “Ekranoplan”. Parallel efforts on prototype craft and theoret- ical analysis gradually built experience and understanding through the 1970s and 1980s leading to the first military service craft based in the Caspian Sea. This was a truly outstanding technological achievement delivered through visionary support from the Russian Navy. In Germany, also in the 1970s, research and prototype craft aimed at using ground effect 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 from government. This work led to ground effect craft suitable for high-speed coastal patrol, though in limited sea conditions. At the beginning of 1970s, Russian engineers Bartini and R.Y. Alexeev invented power-assisted lift arrangements for WIG craft by mounting jet engines in front of the main wing to feed engine exhaust air into the air channel under the wing to create the so-called power-augmented ram wing-in-ground effect craft (PARWIG). This augmented lift improved the take-off and landing performance by reducing take-off speed and distance. The full story of Alexeev’s craft is outlined in Chapter 2 together with other developments from around the world. The technical achievements were highly significant, and it is a pity that the economic situation in Russia through the 1990s was such that the programme had to be stopped. It may be some time before we see machines to equal the KM and Spasatel. In recent years, researchers in China and Russia have mixed air cushion technology into the WIG to create the dynamic air cushion craft (DACC) and dynamic air cushion wing-in-ground effect craft (DACWIG) to produce craft with amphibi- ous capability and much higher transport efficiency at medium cruise speeds in the range 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 or other marine craft. A WIG normally just transits through all the modes except flying in ground effect, but unfortunately the drag forces and motions are the greatest at speeds below take-off, so effective design for the conditions met during the take-off and landing runs is essential to a successful WIG design. The challenges are not over though – quasi-static and dynamic stability of a WIG when flying is strongly influenced by both the flying height and the craft pitch angle. Research into these areas is at an early stage and much more knowledge in the different areas is needed. In this book, we give an outline of the knowledge as it Preface vii exists right now. This provides a starting point, though readers are encouraged to seek out further sources for themselves! Some accidents have occurred on full-scale WIG craft, so that there is some uncertainty as to the safety of WIG for potential operators at present. This is being addressed 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 of operational experience, even if it is at relatively small scale, in order to develop confidence for the commercial industry to gain enthusiasm for this new form of transportation. The IMO guidelines should help a lot in this respect, but practical operations, perhaps following the example of the many SR.N6 hovercraft trials operations and expedition journeys in the 1960s and 1970s, will be needed to prove their capability 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 by aerospace authorities. This has significant cost and operational advantages that should assist in the craft’s commercialisation. WIG are based upon a combination of aircraft and marine technology while being different from either. WIG operate both on water and in air as well as on the edge of both media. A WIG is neither an airplane nor watercraft as such. It is rather different either from airplane industry (sophisticated lightweight structures, high power intensity, automated, heavy certification requirements, expensive construction etc.) or from watercraft (experience based design, relatively heavy structure, robust, low cost, etc.). The WIG borrows from both technologies to achieve a high speed and lightweight, 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 subject outside Russia, so we hope to reach a worldwide audience and encourage interest in this 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. From Chapters 3, 4, 5, 6, 7, 8 and 9, the book describes trim and longitudinal force balance, static hovering performance, aerodynamic characteristics, stability, drag and powering performance, seakeeping quality and manoeuvrability, and model experimental investigations. The materials and structures, power plant selection, and lift and propulsion system selection are introduced in Chapters 10, 11 and 12. In these chapters, the issues related to WIG design are considered as a derivation from aircraft or marine design rather than giving a detailed treatise. In Chapter 13, a general approach to WIG concept specification and design is described. The Postscript discusses prospects for the future and a series of technical issues concerned with the development of WIG that face researchers and engineers in this area at present. There is so much to work on at present. The WIG principle can be applied to a wide envelope of operational speed and environmental conditions, viii Preface 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 form of “traffic lane” agreed at international level and documented on charts. Significant opportunities 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 detailed information 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 presentation 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 the theories presented here. The authors will be pleased to have comments and feedback from readers.

Shanghai, PR China L. Yun Tananger, Norway A. Bliault Mobile, Alabama J. Doo May 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 HPMV Design Subcommittee of CSNAME, including Prof. Xing Wen Hua, Prof. Liang Qi Kang (Managing Director, MARIC), Mr. Wang Gao Zhong (Deputy Managing Director of MARIC and also Former Chief Designer of WIG type SWAN), Prof. Peng, Gui-Hua (Director of HPMV Division, MARIC), Prof. Xie, You-Non (Deputy Chief 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 papers and research during the writing of this book. We also wish to thank the following for material contributions and for permission to use illustrations and photos: Johnny Doo (SSAC), Edwin van Opstal (SE Technology), Boeing Aircraft Company, Flightship Ground Effect Pty Ltd, Fischer Flugmechanik/AFD Airfoil Development and Bob Windt (Universal Hovercraft). Finally we wish to thank our peer review group who provided most valuable feedback on the content and presentation of the book.

ix Contents

1 Wings in Ground Effect ...... 1 Introduction ...... 1 MarineTransportandWIGDevelopment...... 2 Alternative Technologies ...... 3 TheHydrofoil...... 4 TheSES...... 4 TheHovercraft...... 5 Ground Effect for Higher Service Speed ...... 6 Some WIG Technical Terms ...... 7 Ground Effect ...... 8 Dynamic Air Cushion ...... 8 StaticAirCushion...... 9 Basic Principles of Ground Effect ...... 9 Types of WIG ...... 15 ClassicWIG...... 16 PARWIG...... 17 PARWIGAttributes...... 22 PARWIGLimitations...... 22 Military Applications ...... 23 CivilApplications...... 25 Dynamic Air Cushion Craft (DACC) ...... 25 DACCCharacteristics...... 27 DACCApplications...... 27 Dynamic Air Cushion Wing-in-Ground Effect Craft (DACWIG) . . . 27 DACWIGAttributes...... 29 DACWIGApplications...... 32 2 WIG Craft Development ...... 33 Introduction ...... 33 Russian Ekranoplan Development ...... 33 KMor“CaspianSeaMonster”...... 42 UT-1...... 45 Orlyonok and Lun ...... 45

xi xii Contents

Orlyonok’s Accident ...... 47 TheDevelopmentofLun...... 51 KeytoFig.2.20...... 54 Second-Generation WIG ...... 54 Design Studies for Large Commercial Ekranoplan in Russia .... 57 Volga-2...... 59 Recent Small Craft Designs ...... 60 Ivolga...... 60 Amphistar...... 63 Technical Data Summary for Russian WIG Craft ...... 63 WIGDevelopmentinChina...... 65 CSSRCPARWIGCraft...... 67 CASTDPARWIG...... 67 DACWIG Craft Developed by MARIC ...... 70 TheConversionof“SWAN”...... 75 WIGDevelopmentsinGermany...... 77 Tandem Airfoil Flairboats (TAF) ...... 77 Lippisch...... 78 Hoverwing...... 82 WIGintheUnitedStates...... 85 WIGinAustralia...... 87 SeaWing...... 87 Radacraft ...... 89 Flightship...... 89 Concluding Observations ...... 93 3 Longitudinal Force Balance and Trim ...... 95 Introduction ...... 95 Operational Modes ...... 96 Running Trim ...... 98 CentresofEffortandTheirEstimation...... 102 Introduction ...... 102 LongitudinalCentresofForcesActingonWIGCraft...... 103 Centre of Buoyancy (CB) ...... 103 Centre of Hydrodynamic Force Acting on Hull and Side Buoys . . 103 CentreofStaticAirCushionPressure(CP)...... 104 Centre of Aerodynamic Lift of a Single Wing Beyond the GEZ . . 104 Centre of Lift of WIG Main Wing with Bow Thrusters in Ground Effect Zone ...... 104 CentreofLiftofaWholeWIGCraftOperatinginGEZ...... 106 Inﬂuence of Control Mechanisms on Craft Aerodynamic Centres . . . 106 Longitudinal Force Balance ...... 109 Condition for Normal Operation of a WIG in Various Operation Modes ...... 109 Inherent Force-Balance Method ...... 111 Contents xiii

Controllable Equilibrium Method ...... 112 HandlingofWIGDuringTake-Off...... 114 4 Hovering and Slow-Speed Performance ...... 117 Introduction ...... 117 Hovering Performance Requirements ...... 118 Manoeuvring and Landing ...... 118 Low-Speed Operations ...... 118 Hump Speed Transit and Take-Off into GEZ ...... 119 Seakeeping ...... 119 PARWIG Theory from the 1970s ...... 120 Static Hovering Performance of DACWIG and DACC ...... 125 Introduction ...... 125 Configuration of a DACC or DACWIG ...... 126 Static Hovering Performance of DACC and DACWIG ...... 127 Measures for Improving Slow-Speed Performance ...... 138 Inflatable Air Bag ...... 141 Skirt...... 142 Laminar Flow Coating on the Bottoms of Hull and Side Buoys . . 142 Hard Landing Pads ...... 144 5 Aerodynamics in steady Flight ...... 147 Introduction ...... 147 Airfoil Fundamentals ...... 148 An Experimental Investigation of Airfoil Aerodynamics ...... 153 Nomenclature ...... 153 Basic Model ...... 154 Model Tests ...... 157 Discussion...... 175 Drag...... 177 Lift–DragRatio...... 177 PitchingMoment...... 178 Conclusion ...... 178 WIG Aerodynamic Characteristics ...... 179 Factors Influencing WIG Aerodynamic Characteristics ...... 183 Bow Thruster with Guide Vanes or Jet Nozzle ...... 183 Special Main-Wing Profile ...... 184 Aspect Ratio ...... 186 OtherMeasures...... 187 6 Longitudinal and Transverse Stability ...... 189 Introduction ...... 189 ForcesandMoments...... 189 PitchingCentres...... 190 Pitch Stability Design Criteria ...... 191 Height Stability Design Criteria ...... 191 xiv Contents

Main-WingAirfoilandGeometry...... 192 Influence of Flaps ...... 192 TailplaneandElevators...... 193 CentreofGravity...... 193 Influence of Ground Effect on Equilibrium ...... 194 Influence of Bow Thrusters with Jet Nozzle or Guide Vanes .... 194 AutomaticControlSystems...... 195 Stability Analysis ...... 195 Static Longitudinal Stability in and Beyond the GEZ ...... 197 Static Longitudinal Stability of an Aircraft and a WIG Operating Beyond the GEZ ...... 198 Basic Stability Equation ...... 199 WingPitchingCentre...... 200 PitchingPitchingCentre...... 201 FlyingHeightPitchingCentre...... 203 Estimation of Balance Centres ...... 204 Static Longitudinal Stability Criteria ...... 206 Requirements for Positive Static Longitudinal Stability ...... 207 Static Transverse Stability of DACWIG in Steady Flight ...... 210 WIGOperatinginWeakGEZ...... 213 Transverse Stability Criteria ...... 215 Transverse Stability at Slow Speed ...... 216 Transverse Stability During Turning ...... 216 PARWIG Transverse Stability ...... 217 Dynamic Longitudinal Stability over Calm Water ...... 217 BasicAssumptions...... 218 BasicMotionEquations...... 218 Transient Stability During Transition Phases ...... 222 7 Calm Water Drag and Power ...... 225 Introduction ...... 225 WIG Drag Components ...... 230 WIGDragBeforeTake-Off...... 231 HumpDragandItsMinimisation...... 231 EstimationoftheCraftDragBeforeTake-Off...... 234 WIGDragAfterTake-Off...... 239 DragofWIGAfterTake-Off...... 239 PoweringEstimationforWIG...... 243 Performance Based on Wind-Tunnel Test Results of Model withBowThrustersinOperation...... 244 EstimationofWIGTotalDrag...... 245 Drag Prediction by Correlation with Hydrodynamic Model TestResults...... 246 Influences on Drag and Powering Over Calm Water ...... 249 Hull-BorneMode...... 250 Transit Through Main Hump Speed (Fn = 2–4) ...... 250 Contents xv

During Take-Off (Fn = 4.0–8.0) ...... 250 FlyingMode...... 251 8 Seakeeping and Manoeuvrability ...... 255 Introduction ...... 255 DifferentialEquationofWIGMotioninWaves...... 256 CoordinateSystems...... 256 Basic Longitudinal Differential Equations of DACWIG MotioninWaves...... 256 Seakeeping Model Tests ...... 259 Manoeuvrability and Controllability ...... 267 WIGControlinFlight...... 268 The Inﬂuence of a Wind Gust on the Running Trim of WIG in Steady Flight ...... 270 Nonlinear Analysis of WIG Motion ...... 271 Special Cases of Craft Motion ...... 273 Manoeuvring in Hull-Borne Mode ...... 275 Take-OffHandlinginWaves...... 275 Turning Performance ...... 276 Operation of WIG Craft in Higher GEZ ...... 280 9 Model Tests and Aero-hydrodynamic Simulation ...... 283 Introduction ...... 283 Experimental Methodology ...... 284 Static Hovering Experiments on a Rigid Ground Plane ...... 284 Model Tests in a Towing Tank ...... 284 Model Experiments in a Wind Tunnel ...... 285 Radio-controlled Model Tests on Open Water and Catapult Model Testing Over Ground ...... 285 WIG Model Scaling Rules ...... 286 ScalingParametersforWIG...... 286 Reynold’s Number ...... 286 Euler Number (Hq)andRelationtoCushionPressureRatio.... 294 Wind-Tunnel Testing ...... 294 Bow Thruster or Lift Fan Non-dimensional Characteristics ofDACCandDACWIG...... 297 Froude Number, Fn ...... 299 Weber Number, We ...... 299 Other Scaling Terms for Towing Tank Test Models ...... 300 StructuralSimulation...... 301 ScalingCriteria...... 301 Model Test Procedures ...... 302 10 Structural Design and Materials ...... 307 Introduction ...... 307 Design Loads ...... 309 Waterborne and Pre-take-off Loads ...... 310 xvi Contents

Take-Off and Landing Loads ...... 311 Ground-Manoeuvring Loads ...... 312 Flight Loads ...... 313 Impact and Handling Loads ...... 314 Design Approach ...... 315 Metallic Materials ...... 316 CompositeMaterials...... 318 Sandwich Construction ...... 320 Fatigue, Damage Tolerance and Fail-Safe ...... 323 WIG Structural Design Concepts and Considerations ...... 324 BasicDesignConsiderations...... 324 11 Power plant and Transmission ...... 337 Introduction ...... 337 WIGPowerPlantTypeSelection...... 338 InternalCombustionEngines...... 339 Turbofan/Turboshaft/Turboprop Engines ...... 341 WIG Application Special Requirements ...... 345 Marinisation...... 345 Altitude Operations ...... 346 PowerPlantInstallationDesign...... 347 Pylon/NacelleInstallation...... 347 EngineandSystemCooling...... 348 InternalSystemsInstallation...... 348 WaterSpray...... 349 EngineandSystemCooling...... 349 IceProtection...... 351 TransmissionSystems...... 351 Drive Shaft ...... 351 Transmission...... 352 12 Lift and Propulsion Systems ...... 355 Introduction ...... 355 Power-AugmentedLift...... 356 Independent Lift Systems ...... 359 Propulsion Systems ...... 361 PropellerandDuctedFanCharacteristics...... 363 TurbofanSystem...... 367 Integrated Lift/Propulsion System ...... 369 Propulsor Selection and Design ...... 372 13 Concept Design ...... 373 Introduction ...... 373 General WIG Application Issues ...... 376 Technical Factors ...... 377 Operational Factors ...... 379 Contents xvii

WIG Subtypes and Their Application ...... 381 WIGPreliminaryDesign...... 383 Design Sequence ...... 384 Functional Speciﬁcation for a WIG ...... 385 Design Requirements ...... 388 Safety Codes for WIG Craft ...... 393 Basic Concepts ...... 393 Supplementary Safety Criteria for DACWIG ...... 394 Setting Up a Preliminary Conﬁguration ...... 396 Procedure for Overall Preliminary Design ...... 414 Determination of WIG Aerodynamic and Hydrodynamic Characteristics...... 414 WIGDetailedDesign...... 415 Postscript ...... 417 Glossary ...... 423 References and Resources ...... 433 Subject Index ...... 441