Helicopter Flight Dynamics: The Theory and Application of Flying Qualities and Simulation Modelling, Second Edition

669 Pages·2007·7.59 MB·English

by  Gareth D. Padfield(auth.)

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HELICOPTER FLIGHT DYNAMICS
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HELICOPTER FLIGHT DYNAMICS
The Theory and Application
of
Flying Qualities
and
Simulation Modelling
Second Edition
Gareth D. Padfield
BSc,PhD,CEng,FRAeS
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(cid:2)C 1996,2007byG.D.Padfield
BlackwellPublishingeditorialoffices:
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Firstpublished1996
Secondeditionpublished2007
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BritishLibraryCataloguing-in-PublicationData:
Padfield,G.D.
Helicopter flight dynamics : the theory and application of flying qualities and simulation
modelling/GarethD.Padfield.–2nded.
p.cm.
Includesbibliographicalreferencesandindex.
ISBN-13:978-1-4051-1817-0(hardback:alk.paper)
ISBN-10:1-4051-1817-2(hardback:alk.paper)
1.Helicopters–Aerodynamics. 2.Helicopters–Handlingcharacteristics. I.Title.
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iv
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Tomyfamily
Joey,JudeandGeorge
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Contents
Prefacetofirstedition xiii
Prefacetosecondedition xvii
Copyrightacknowledgements xxi
Notation xxiii
Listofabbreviations xxxiii
Chapter1 Introduction
1.1Simulationmodelling 1
1.2Flyingqualities 3
1.3Missingtopics 4
1.4Simpleguidetothebook 5
Chapter2 Helicopterflightdynamics–anintroductorytour
2.1Introduction 9
2.2Fourreferencepoints 10
2.2.1Themissionandpilotingtasks 11
2.2.2Theoperationalenvironment 14
2.2.3Thevehicleconfiguration,dynamicsandflightenvelope 15
Rotorcontrols 15
Twodistinctflightregimes 17
Rotorstallboundaries 20
2.2.4Thepilotandpilot–vehicleinterface 22
2.2.5Re´sume´ofthefourreferencepoints 24
2.3Modellinghelicopterflightdynamics 25
Theproblemdomain 25
Multipleinteractingsubsystems 26
Trim,stabilityandresponse 28
Theflappingrotorinvacuo 30
Theflappingrotorinair–aerodynamicdamping 33
Flappingderivatives 36
◦
Thefundamental90 phaseshift 36
Hubmomentsandrotor/fuselagecoupling 38
Linearizationingeneral 41
Stabilityandcontrolre´sume´ 42
ThestaticstabilityderivativeMw 43
Rotorthrust,inflow, Zwandverticalgustresponseinhover 46
Gustresponseinforwardflight 48
Vector-differentialformofequationsofmotion 50
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viii Contents
Validation 52
Inversesimulation 57
Modellingreview 58
2.4Flyingqualities 59
Pilotopinion 60
Quantifyingqualityobjectively 61
Frequencyandamplitude–exposingthenaturaldimensions 62
Stability–earlysurprisescomparedwithaeroplanes 63
Pilot-in-the-loopcontrol;attackingamanoeuvre 66
Bandwidth–aparameterforallseasons? 67
Flyingamissiontaskelement 70
Thecliffedgeandcarefreehandling 71
Agilityfactor 72
Pilot’sworkload 73
Inceptorsanddisplays 75
Operationalbenefitsofflyingqualities 75
Flyingqualitiesreview 77
2.5Designforflyingqualities;stabilityandcontrolaugmentation 78
Impurityofprimaryresponse 79
Strongcross-couplings 79
Responsedegradationatflightenvelopelimits 80
Poorstability 80
Therotorasacontrolfilter 81
Artificialstability 81
2.6Chapterreview 84
Chapter3 Modellinghelicopterflightdynamics:buildingasimulationmodel
3.1Introductionandscope 87
3.2Theformulationofhelicopterforcesandmomentsinlevel1modelling 91
3.2.1Mainrotor 93
Bladeflappingdynamics–introduction 93
Thecentre-springequivalentrotor 96
Multi-bladecoordinates 102
Rotorforcesandmoments 108
Rotortorque 114
Rotorinflow 115
Momentumtheoryforaxialflight 116
Momentumtheoryinforwardflight 119
Local-differentialmomentumtheoryanddynamicinflow 125
Rotorflapping–furtherconsiderationsofthecentre-spring
approximation 128
Rotorin-planemotion–lead–lag 135
Rotorbladepitch 138
Groundeffectoninflowandinducedpower 139
3.2.2Thetailrotor 142
3.2.3Fuselageandempennage 146
Thefuselageaerodynamicforcesandmoments 146
Theempennageaerodynamicforcesandmoments 149
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Contents ix
3.2.4Powerplantandrotorgovernor 152
3.2.5Flightcontrolsystem 154
Pitchandrollcontrol 154
Yawcontrol 158
Heavecontrol 158
3.3Integratedequationsofmotionofthehelicopter 159
3.4Beyondlevel1modelling 162
3.4.1Rotoraerodynamicsanddynamics 163
Rotoraerodynamics 163
Modellingsectionlift,dragandpitchingmoment 164
Modellinglocalincidence 167
Rotordynamics 168
3.4.2Interactionalaerodynamics 171
Appendix3A Framesofreferenceandcoordinatetransformations 175
3A.1Theinertialmotionoftheaircraft 175
3A.2Theorientationproblem–angularcoordinatesoftheaircraft 180
3A.3Componentsofgravitationalaccelerationalongtheaircraftaxes 181
3A.4Therotorsystem–kinematicsofabladeelement 182
3A.5Rotorreferenceplanes–hub,tippathandno-feathering 184
Chapter4 Modellinghelicopterflightdynamics:trimandstabilityanalysis
4.1Introductionandscope 187
4.2Trimanalysis 192
4.2.1Thegeneraltrimproblem 194
4.2.2Longitudinalpartialtrim 196
4.2.3Lateral/directionalpartialtrim 201
4.2.4Rotorspeed/torquepartialtrim 203
4.2.5Balanceofforcesandmoments 204
4.2.6Controlanglestosupporttheforcesandmoments 204
4.3Stabilityanalysis 208
4.3.1Linearization 209
4.3.2Thederivatives 214
Thetranslationalvelocityderivatives 215
Theangularvelocityderivatives 224
Thecontrolderivatives 231
Theeffectsofnon-uniformrotorinflowondampingandcontrol
derivatives 234
Somereflectionsonderivatives 235
4.3.3Thenaturalmodesofmotion 236
Thelongitudinalmodes 241
Thelateral/directionalmodes 247
Comparisonwithflight 250
Appendix4A Theanalysisoflineardynamicsystems(withspecialreferenceto
6DoFhelicopterflight) 252
Appendix4B Thethreecasehelicopters:Lynx,Bo105andPuma 261
4B.1Aircraftconfigurationparameters 261
TheDRA(RAE)researchLynx,ZD559 261
TheDLRresearchBo105,S123 261
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TheDRA(RAE)researchPuma,SA330 263
Fuselageaerodynamiccharacteristics 264
Empennageaerodynamiccharacteristics 268
4B.2Stabilityandcontrolderivatives 269
4B.3Tablesofstabilityandcontrolderivativesandsystemeigenvalues 277
Appendix4C Thetrimorientationproblem 293
Chapter5 Modellinghelicopterflightdynamics:stabilityunderconstraint
andresponseanalysis
5.1Introductionandscope 297
5.2Stabilityunderconstraint 298
5.2.1Attitudeconstraint 299
5.2.2Flight-pathconstraint 306
Longitudinalmotion 306
Lateralmotion 310
5.3Analysisofresponsetocontrols 315
5.3.1General 315
5.3.2Heaveresponsetocollectivecontrolinputs 317
Responsetocollectiveinhover 317
Responsetocollectiveinforwardflight 323
5.3.3Pitchandrollresponsetocyclicpitchcontrolinputs 325
Responsetostepinputsinhover–generalfeatures 325
Effectsofrotordynamics 327
Stepresponsesinhover–effectofkeyrotorparameters 327
Responsevariationswithforwardspeed 330
Stabilityversusagility–contributionofthehorizontaltailplane 331
Comparisonwithflight 332
5.3.4Yaw/rollresponsetopedalcontrolinputs 338
5.4Responsetoatmosphericdisturbances 344
Modellingatmosphericdisturbances 346
Modellinghelicopterresponse 348
Ridequalities 350
Chapter6 Flyingqualities:objectiveassessmentandcriteriadevelopment
6.1Generalintroductiontoflyingqualities 355
6.2Introductionandscope:theobjectivemeasurementofquality 360
6.3Rollaxisresponsecriteria 364
6.3.1Taskmarginandmanoeuvrequickness 364
6.3.2Moderatetolargeamplitude/lowtomoderatefrequency:quickness
andcontrolpower 371
6.3.3Smallamplitude/moderatetohighfrequency:bandwidth 378
Earlyeffortsinthetimedomain 378
Bandwidth 381
Phasedelay 386
Bandwidth/phasedelayboundaries 387
Civilapplications 389
Themeasurementofbandwidth 391
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Contents xi
Estimatingωbwandτp 397
Controlsensitivity 399
6.3.4Smallamplitude/lowtomoderatefrequency:dynamicstability 401
6.3.5Trimandquasi-staticstability 402
6.4Pitchaxisresponsecriteria 404
6.4.1Moderatetolargeamplitude/lowtomoderatefrequency:quickness
andcontrolpower 404
6.4.2Smallamplitude/moderatetohighfrequency:bandwidth 408
6.4.3Smallamplitude/lowtomoderatefrequency:dynamicstability 410
6.4.4Trimandquasi-staticstability 413
6.5Heaveaxisresponsecriteria 417
6.5.1Criteriaforhoverandlowspeedflight 420
6.5.2Criteriafortorqueandrotorspeedduringverticalaxismanoeuvres 424
6.5.3Heaveresponsecriteriainforwardflight 424
6.5.4Heaveresponsecharacteristicsinsteepdescent 427
6.6Yawaxisresponsecriteria 429
6.6.1Moderatetolargeamplitude/lowtomoderatefrequency:quickness
andcontrolpower 430
6.6.2Smallamplitude/moderatetohighfrequency:bandwidth 433
6.6.3Smallamplitude/lowtomoderatefrequency:dynamicstability 433
6.6.4Trimandquasi-staticstability 436
6.7Cross-couplingcriteria 437
6.7.1Pitch-to-rollandroll-to-pitchcouplings 437
6.7.2Collectivetopitchcoupling 440
6.7.3Collectivetoyawcoupling 440
6.7.4Sidesliptopitchandrollcoupling 440
6.8Multi-axisresponsecriteriaandnovel-responsetypes 442
6.8.1Multi-axisresponsecriteria 442
6.8.2Novelresponsetypes 444
6.9Objectivecriteriarevisited 447
Chapter7 Flyingqualities:subjectiveassessmentandothertopics
7.1Introductionandscope 455
7.2Thesubjectiveassessmentofflyingquality 456
7.2.1Pilothandlingqualitiesratings–HQRs 457
7.2.2Conductingahandlingqualitiesexperiment 464
Designingamissiontaskelement 464
Evaluatingrollaxishandlingcharacteristics 466
7.3Specialflyingqualities 478
7.3.1Agility 478
Agilityasamilitaryattribute 478
Theagilityfactor 481
Relatingagilitytohandlingqualitiesparameters 484
7.3.2Theintegrationofcontrolsanddisplaysforflightindegradedvisual
environments 487
FlightinDVE 487
Pilotagefunctions 488
FlyinginDVE 489
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xii Contents
Theusablecueenvironment 490
UCEaugmentationwithoverlaidsymbology 496
7.3.3Carefreeflyingqualities 500
7.4Pilot’scontrollers 508
7.5Thecontributionofflyingqualitiestooperationaleffectivenessandthesafety
offlight 511
Chapter8 Flyingqualities:formsofdegradation
8.1Introductionandscope 517
8.2Flightindegradedvisualenvironments 519
8.2.1Recappingtheusablecueenvironment 520
8.2.2Visualperceptioninflightcontrol–opticalflowandmotionparallax 523
8.2.3Timetocontact;opticaltau,τ 532
8.2.4τ controlinthedeceleration-to-stopmanoeuvre 536
8.2.5Tau-coupling–aparadigmforsafetyinaction 538
8.2.6Terrain-followingflightindegradedvisibility 545
τ ontherisingcurve 548
8.3Handlingqualitiesdegradationthroughflightsystemfailures 559
8.3.1Methodologyforquantifyingflyingqualitiesfollowingflightfunction
failures 562
8.3.2Lossofcontrolfunction 564
Tailrotorfailures 564
8.3.3Malfunctionofcontrol–hard-overfailures 568
8.3.4Degradationofcontrolfunction–actuatorratelimiting 574
8.4Encounterswithatmosphericdisturbances 576
8.4.1Helicopterresponsetoaircraftvortexwakes 578
Thewakevortex 578
Hazardseveritycriteria 579
Analysisofencounters–attituderesponse 587
Analysisofencounters–verticalresponse 588
8.4.2Severityoftransientresponse 593
8.5ChapterReview 597
Appendix8A HELIFLIGHTandFLIGHTLABattheUniversityofLiverpool 599
FLIGHTLAB 601
Immersivecockpitenvironment 602
References 608
Index 633