Principles of Flight Simulation (Aerospace Series (PEP))

104 Pages·2009·0.89 MB·English

by  David Allerton

Contents
About the Author xiii
Preface xv
Glossary xvii
1 Introduction 1
1.1 Historical Perspective 1
1.1.1 TheFirst40YearsofFlight1905–1945 1
1.1.2 AnalogueComputing,1945–1965 3
1.1.3 DigitalComputing,1965–1985 5
1.1.4 TheMicroelectronicsRevolution,1985–present 6
1.2 The Case for Simulation 9
1.2.1 Safety 9
1.2.2 FinancialBenefits 10
1.2.3 TrainingTransfer 11
1.2.4 EngineeringFlightSimulation 13
1.3 The Changing Role of Simulation 14
1.4 The Organization of a Flight Simulator 16
1.4.1 EquationsofMotion 16
1.4.2 AerodynamicModel 17
1.4.3 EngineModel 18
1.4.4 DataAcquisition 18
1.4.5 GearModel 19
1.4.6 WeatherModel 19
1.4.7 VisualSystem 20
1.4.8 SoundSystem 21
1.4.9 MotionSystem 21
1.4.10 ControlLoading 22
1.4.11 InstrumentDisplays 23
1.4.12 NavigationSystems 23
1.4.13 Maintenance 24
1.5 The Concept of Real-time Simulation 24
1.6 Pilot Cues 27
1.6.1 VisualCueing 28
1.6.2 MotionCueing 29
1.7 Training versus Simulation 30
1.8 Examples of Simulation 32
1.8.1 CommercialFlightTraining 32
viii Contents
1.8.2 MilitaryFlightTraining 34
1.8.3 AbInitioFlightTraining 34
1.8.4 LandVehicleSimulators 34
1.8.5 EngineeringFlightSimulators 35
1.8.6 AptitudeTesting 36
1.8.7 Computer-basedTraining 36
1.8.8 MaintenanceTraining 37
References 37
2 Principles of Modelling 41
2.1 ModellingConcepts 41
2.2 Newtonian Mechanics 43
2.3 Axes Systems 51
2.4 Differential Equations 53
2.5 Numerical Integration 56
2.5.1 ApproximationMethods 56
2.5.2 First-orderMethods 58
2.5.3 Higher-orderMethods 59
2.6 Real-time Computing 63
2.7 Data Acquisition 67
2.7.1 DataTransmission 67
2.7.2 DataAcquisition 69
2.8 Flight Data 74
2.9 Interpolation 77
2.10 DistributedSystems 82
2.11 A Real-time Protocol 91
2.12 Problems in Modelling 92
References 96
3 Aircraft Dynamics 97
3.1 Principles of Flight Modelling 97
3.2 The Atmosphere 98
3.3 Forces 100
3.3.1 AerodynamicLift 100
3.3.2 AerodynamicSideforce 104
3.3.3 AerodynamicDrag 105
3.3.4 PropulsiveForces 106
3.3.5 GravitationalForce 107
3.4 Moments 107
3.4.1 StaticStability 109
3.4.2 AerodynamicMoments 111
3.4.3 AerodynamicDerivatives 113
3.5 Axes Systems 114
3.5.1 TheBodyFrame 115
3.5.2 StabilityAxes 117
3.5.3 WindAxes 117
3.5.4 InertialAxes 118
3.5.5 TransformationbetweenAxes 118
3.5.6 Earth-centredEarth-fixed(ECEF)Frame 119
3.5.7 LatitudeandLongitude 122
3.6 Quaternions 122
Contents ix
3.7 Equationsof Motion 124
3.8 Propulsion 127
3.8.1 PistonEngines 128
3.8.2 JetEngines 136
3.9 The Landing Gear 138
3.10 The EquationsCollected 143
3.11 The EquationsRevisited – Long Range Navigation 148
3.11.1 CoriolisAcceleration 150
References 154
4 Simulation of Flight Control Systems 157
4.1 The Laplace Transform 157
4.2 Simulation of Transfer Functions 161
4.3 PID Control Systems 163
4.4 Trimming 169
4.5 Aircraft Flight Control Systems 171
4.6 The Turn Coordinator and the Yaw Damper 172
4.7 The Auto-throttle 176
4.8 Vertical Speed Management 179
4.9 AltitudeHold 182
4.10 Heading Hold 185
4.11 Localizer Tracking 189
4.12 Auto-land Systems 191
4.13 Flight Management Systems 195
References 201
5 Aircraft Displays 203
5.1 Principles of Display Systems 203
5.2 Line Drawing 205
5.3 Character Generation 211
5.4 2D Graphics Operations 214
5.5 Textures 216

5.6 OpenGL 219
5.7 Simulation of Aircraft Instruments 227
5.8 Simulation of EFIS Displays 235
5.8.1 AttitudeIndicator 237
5.8.2 Altimeter 239
5.8.3 AirspeedIndicator 240
5.8.4 CompassCard 241
5.9 Head-up Displays 242
References 246
6 Simulation of Aircraft NavigationSystems 247
6.1 Principles of Navigation 247
6.2 Navigation Computations 250
6.3 Map Projections 252
6.4 Primary Flight Information 254
6.4.1 AttitudeIndicator 254
6.4.2 Altimeter 255
6.4.3 AirspeedIndicator 255
x Contents
6.4.4 Compass 255
6.4.5 VerticalSpeedIndicator 255
6.4.6 TurnIndicator 255
6.4.7 SlipBall 255
6.5 AutomaticDirection Finding (ADF) 255
6.6 VHF Omnidirectional Range (VOR) 257
6.7 DistanceMeasuring Equipment (DME) 258
6.8 Instrument Landing Systems (ILS) 259
6.9 The Flight Director 260
6.10 Inertial NavigationSystems 263
6.10.1 Axes 264
6.10.2 INSEquations 264
6.10.3 INSErrorModel 268
6.10.4 ValidationoftheINSModel 272
6.11 Global PositioningSystems 274
References 282
Further Reading 283
7 Model Validation 285
7.1 Simulator Qualification and Approval 285
7.2 Model Validation Methods 288
7.2.1 CockpitGeometry 291
7.2.2 StaticTests 291
7.2.3 Open-loopTests 294
7.2.4 Closed-loopTests 294
7.3 Latency 298
7.4 Performance Analysis 305
7.5 LongitudinalDynamics 312
7.6 Lateral Dynamics 323
7.7 Model Validation in Perspective 328
References 329
8 Visual Systems 331
8.1 Background 331
8.2 The Visual System Pipeline 332
8.3 3D Graphics Operations 336
8.4 Real-time Image Generation 343
8.4.1 ARudimentaryReal-timeWireFrameIGSystem 343
8.4.2 AnOpenGLReal-timeIGSystem 347
8.4.3 AnOpenGLReal-timeTexturedIGSystem 350
8.4.4 AnOpenSceneGraphIGSystem 352
8.5 Visual Database Management 364
8.6 Projection Systems 370
8.7 Problems in Visual Systems 374
References 376
9 The Instructor Station 377
9.1 Education,Training and Instruction 377
9.2 Part-task Training and Computer-based Training 378
9.3 The Role of the Instructor 379
Contents xi
9.4 Designing theUser Interface 380
9.4.1 HumanFactors 382
9.4.2 ClassificationofUserOperations 383
9.4.3 StructureoftheUserInterface 384
9.4.4 UserInputSelections 388
9.4.5 InstructorCommands 394
9.5 Real-time Interaction 398
9.6 Map Displays 404
9.7 Flight Data Recording 409
9.8 Scripting 413
References 421
10 Motion Systems 423
10.1 Motionor No Motion? 423
10.2 PhysiologicalAspects of Motion 425
10.3 Actuator Configurations 428
10.4 Equationsof Motion 432
10.5 Implementation of a Motion System 436
10.6 HydraulicActuation 443
10.7 ModellingHydraulic Actuators 447
10.8 Limitationsof MotionSystems 451
10.9 Future Motion Systems 453
References 454
Index 457

About the Author
DavidAllertonobtainedaBScinComputerSystemsEngineeringfromRugbyCollegeofEngineer-
ingTechnologyin1972andaPostgraduateCertificateinEducation(PGCE) inphysicaleducation
from Loughborough College of Education in 1973. He obtained his PhD from the University of
Cambridge in 1977 for research on parallel computing before joiningMarconi Space and Defence
Systems as a Principal Engineer developingsoftware for embedded systems. He was appointed as
a Lecturer in the Department of Electronics at the University of Southampton in 1981 and was
promoted to a Senior Lectureship in 1987. He moved to the College of Aeronautics at Cranfield
Universityas Professor ofAvionicsin 1991, establishingtheDepartment of Avionics.In 2002,he
was appointed to the Chair in Computer Systems Engineering at the Universityof Sheffield.
ProfessorAllertonhasdevelopedfiveflightsimulatorsattheuniversitiesofSouthampton,Cran-
fieldandSheffield,andisamemberandpast-ChairmanoftheRoyalAeronauticalSociety’sFlight
Simulation Group. He has also served on the UK Foresight Panel for Defence and Aerospace and
National Advisory Committees for avionics and also for synthetic environments. In 1998, he was
awarded £750,000 by the Higher Education Funding Council for England (HEFCE) to establish a
research centre in flight simulation at Cranfield University. He was Director of the annual short
course in flight simulation at Cranfield University from 1992 until 2001. He is a Fellow of the
Institution of Engineering Technology and a Fellow of the Royal Aeronautical Society and is a
Chartered Engineer.
His research interests include computer architecture, real-time software, computer graphics,
air-traffic management, flight simulation, avionics and operating systems. He holds a private pilot
licence with an IMC rating and represents Yorkshireat tennis (over 55).

Preface
I was lucky – I was a schoolboy in the 1960s. In those days, we mended our own punctures
and learnt to take a motorcycle engine apart from first principles. Later on, as a student in the
1970s, I worked on the early computers. They came with circuit diagrams and if they had a fault,
as they often did, we laid the schematics out on the bench and fixed it. It was open-season for
initiative– we designed our own operating systems, invented our own computer languages and
wroteourowncompilers.Weknewhexadecimal,couldreadbinarypapertapesandwroteinterrupt
service routines. The computers were slow, so we had to design efficient algorithms and because
there was very littlememory, efficient organization of data was paramount.
So, in the early 1980s, when we developed microprocessor systems, graphics cards and array
processors, building a flight simulator seemed a simple and natural progression. At the time, the
sumtotalofmyaeronauticalknowledgewasthatthepilotsatatthefrontoftheaeroplaneandthe
airstewardesssatattheback.Infact,talkingtoseveralpilots,eventhevalidityofthisassumption
turnsouttobesomewhatflawed.Nevertheless,Iembarkedonthedesignofaflightsimulatorand,
some twenty years on, having built five simulators and written over 250,000 lines of code, that
practical knowledgeforms the basis of this book.
Imakenoapologyforbeinganengineer.Ifeelstronglythatengineeringisanapplieddiscipline
and that the subject is learnt by understanding the theory and then applying it to problems1.
Flightsimulationbringstogethermathematics,computerscience,electronics,mechanicsandcontrol
theory.In otherwords,flightsimulationisanapplicationofsystemsengineeringanditprovidesa
fertileplaygroundtoenableundergraduateandpostgraduatestudentstodeveloptheirunderstanding
and practice new skills in these subjects. The book focuses on software and algorithms because
these are the activities that underpin flight simulation. We were not daunted by machine code
programmingoftheearlycomputersofthe1970sandlikewise,studentsinthetwenty-firstcentury
shouldnotbeintimidatedbythecomplexityanddiversityofsoftwareneededforaflightsimulator.
By the very nature of the subject, the book is wide ranging, which lends itself to criticism that
thetopicsarenotcoveredinsufficientdepth.However,thebooktriestobalancebreadthanddepth,
providingthemajorityofthesoftwareneededtoconstructaflightsimulator,ortodevelopsimulator
modules. The flight simulator covered in this book emphasizes modular design, at the level of a
distributednetworkofcomputersandalsoatthelevelofsoftwaremodules.Theaimistoproduce
a system of ‘Lego’ bricks, where a module can easily be removed or improved, for example, to
develop an aircraft model, or a display or a flight control system.
Thefirstchapterprovidesthehistoricalbackgroundandreviewsthetrendsandconceptsbehind
flight simulation, emphasizing its role in flight training. The general principles behind systems
modelling are introduced in Chapter 2 to provide the background for aircraft dynamics covered
in Chapter 3, which formulates the equations of motion used in a modern flight simulator. The
systems perspective is explored further in Chapter 4, where the design methods used in the flight
control systems found in modern aircraft are outlined. Chapter 5 concentrates on the computer
graphics used in simulator displays and the use of OpenGL in real-time graphics applications.
1‘Thatwhichwemustlearntodo,welearnbydoing’–Aristotle.