Helicopter Flight Dynamics (Aiaa Education Series)

HELICOPTER FLIGHT DYNAMICS......Page 1
Contents......Page 9
Preface to first edition......Page 15
Preface to second edition......Page 19
Copyright acknowledgements......Page 23
Notation......Page 25
List of abbreviations......Page 35
1.1 Simulation modelling......Page 39
1.2 Flying qualities......Page 41
1.3 Missing topics......Page 42
1.4 Simple guide to the book......Page 43
2.1 Introduction......Page 47
2.2 Four reference points......Page 48
2.2.1 The mission and piloting tasks......Page 49
2.2.2 The operational environment......Page 52
Rotor controls......Page 53
Two distinct flight regimes......Page 55
Rotor stall boundaries......Page 58
2.2.4 The pilot and pilot-vehicle interface......Page 60
2.2.5 Resume of the four reference points......Page 62
The problem domain......Page 63
Multiple interacting subsystems......Page 64
Trim, stability and response......Page 66
The flapping rotor in vacuo......Page 68
The flapping rotor in air – aerodynamic damping......Page 71
The fundamental 90deg phase shift......Page 74
Hub moments and rotor/fuselage coupling......Page 76
Linearization in general......Page 79
Stability and control resume......Page 80
The static stability derivative Mw......Page 81
Rotor thrust, inflow, Zw and vertical gust response in hover......Page 84
Gust response in forward flight......Page 86
Vector-differential form of equations of motion......Page 88
Validation......Page 90
Inverse simulation......Page 95
Modelling review......Page 96
2.4 Flying qualities......Page 97
Pilot opinion......Page 98
Quantifying quality objectively......Page 99
Frequency and amplitude – exposing the natural dimensions......Page 100
Stability – early surprises compared with aeroplanes......Page 101
Pilot-in-the-loop control; attacking a manoeuvre......Page 104
Bandwidth – a parameter for all seasons?......Page 105
Flying a mission task element......Page 108
The cliff edge and carefree handling......Page 109
Agility factor......Page 110
Pilot’s workload......Page 111
Operational benefits of flying qualities......Page 113
Flying qualities review......Page 115
2.5 Design for flying qualities; stability and control augmentation......Page 116
Strong cross-couplings......Page 117
Poor stability......Page 118
Artificial stability......Page 119
2.6 Chapter review......Page 122
3.1 Introduction and scope......Page 125
3.2 The formulation of helicopter forces and moments in level 1 modelling......Page 129
Blade flapping dynamics – introduction......Page 131
The centre-spring equivalent rotor......Page 134
Multi-blade coordinates......Page 140
Rotor forces and moments......Page 146
Rotor torque......Page 152
Rotor inflow......Page 153
Momentum theory for axial flight......Page 154
Momentum theory in forward flight......Page 157
Local-differential momentum theory and dynamic inflow......Page 163
Rotor flapping–further considerations of the centre-spring approximation......Page 166
Rotor in-plane motion – lead–lag......Page 173
Rotor blade pitch......Page 176
Ground effect on inflow and induced power......Page 177
3.2.2 The tail rotor......Page 180
The fuselage aerodynamic forces and moments......Page 184
The empennage aerodynamic forces and moments......Page 187
3.2.4 Powerplant and rotor governor......Page 190
Pitch and roll control......Page 192
Heave control......Page 196
3.3 Integrated equations of motion of the helicopter......Page 197
3.4 Beyond level 1 modelling......Page 200
Rotor aerodynamics......Page 201
Modelling section lift, drag and pitching moment......Page 202
Modelling local incidence......Page 205
Rotor dynamics......Page 206
3.4.2 Interactional aerodynamics......Page 209
3A.1 The inertial motion of the aircraft......Page 213
3A.2 The orientation problem … angular coordinates of the aircraft......Page 218
3A.3 Components of gravitational acceleration along the aircraft axes......Page 219
3A.4 The rotor system … kinematics of a blade element......Page 220
3A.5 Rotor reference planes … hub, tip path and no-feathering......Page 222
4.1 Introduction and scope......Page 225
4.2 Trim analysis......Page 230
4.2.1 The general trim problem......Page 232
4.2.2 Longitudinal partial trim......Page 234
4.2.3 Lateral/directional partial trim......Page 239
4.2.4 Rotorspeed/torque partial trim......Page 241
4.2.6 Control angles to support the forces and moments......Page 242
4.3 Stability analysis......Page 246
4.3.1 Linearization......Page 247
4.3.2 The derivatives......Page 252
The translational velocity derivatives......Page 253
The angular velocity derivatives......Page 262
The control derivatives......Page 269
The effects of non-uniform rotor inflow on damping and control derivatives......Page 272
Some reflections on derivatives......Page 273
4.3.3 The natural modes of motion......Page 274
The longitudinal modes......Page 279
The lateral/directional modes......Page 285
Comparison with flight......Page 288
Appendix 4A The analysis of linear dynamic systems (with special reference to 6 DoF helicopter flight)......Page 290
The DRA (RAE) research Lynx, ZD559......Page 299
The DLR research Bo105, S123......Page 301
The DRA (RAE) research Puma, SA330......Page 303
Fuselage aerodynamic characteristics......Page 305
Empennage aerodynamic characteristics......Page 306
4B.2 Stability and control derivatives......Page 307
4B.3 Tables of stability and control derivatives and system eigenvalues......Page 315
Appendix 4C The trim orientation problem......Page 331
5.1 Introduction and scope......Page 335
5.2 Stability under constraint......Page 336
5.2.1 Attitude constraint......Page 337
Longitudinal motion......Page 344
Lateral motion......Page 348
5.3.1 General......Page 353
Response to collective in hover......Page 355
Response to collective in forward flight......Page 361
Response to step inputs in hover – general features......Page 363
Step responses in hover – effect of key rotor parameters......Page 365
Response variations with forward speed......Page 368
Stability versus agility – contribution of the horizontal tailplane......Page 369
Comparison with flight......Page 370
5.3.4 Yaw/roll response to pedal control inputs......Page 376
5.4 Response to atmospheric disturbances......Page 382
Modelling atmospheric disturbances......Page 384
Modelling helicopter response......Page 386
Ride qualities......Page 388
6.1 General introduction to flying qualities......Page 393
6.2 Introduction and scope: the objective measurement of quality......Page 398
6.3.1 Task margin and manoeuvre quickness......Page 402
6.3.2 Moderate to large amplitude/low to moderate frequency: quickness and control power......Page 409
Early efforts in the time domain......Page 416
Bandwidth......Page 419
Phase delay......Page 424
Bandwidth/phase delay boundaries......Page 425
Civil applications......Page 427
The measurement of bandwidth......Page 429
Estimating Wbw and τp......Page 435
Control sensitivity......Page 437
6.3.4 Small amplitude/low to moderate frequency: dynamic stability......Page 439
6.3.5 Trim and quasi-static stability......Page 440
6.4.1 Moderate to large amplitude/low to moderate frequency: quickness and control power......Page 442
6.4.2 Small amplitude/moderate to high frequency: bandwidth......Page 446
6.4.3 Small amplitude/low to moderate frequency: dynamic stability......Page 448
6.4.4 Trim and quasi-static stability......Page 451
6.5 Heave axis response criteria......Page 455
6.5.1 Criteria for hover and low speed flight......Page 458
6.5.3 Heave response criteria in forward flight......Page 462
6.5.4 Heave response characteristics in steep descent......Page 465
6.6 Yaw axis response criteria......Page 467
6.6.1 Moderate to large amplitude/low to moderate frequency: quickness and control power......Page 468
6.6.3 Small amplitude/low to moderate frequency: dynamic stability......Page 471
6.6.4 Trim and quasi-static stability......Page 474
6.7.1 Pitch-to-roll and roll-to-pitch couplings......Page 475
6.7.4 Sideslip to pitch and roll coupling......Page 478
6.8.1 Multi-axis response criteria......Page 480
6.8.2 Novel response types......Page 482
6.9 Objective criteria revisited......Page 485
7.1 Introduction and scope......Page 493
7.2 The subjective assessment of flying quality......Page 494
7.2.1 Pilot handling qualities ratings … HQRs......Page 495
Designing a mission task element......Page 502
Evaluating roll axis handling characteristics......Page 504
Agility as a military attribute......Page 516
The agility factor......Page 519
Relating agility to handling qualities parameters......Page 522
Flight in DVE......Page 525
Pilotage functions......Page 526
Flying in DVE......Page 527
The usable cue environment......Page 528
UCE augmentation with overlaid symbology......Page 534
7.3.3 Carefree flying qualities......Page 538
7.4 Pilot's controllers......Page 546
7.5 The contribution of flying qualities to operational effectiveness and the safety of flight......Page 549
8.1 Introduction and scope......Page 555
8.2 Flight in degraded visual environments......Page 557
8.2.1 Recapping the usable cue environment......Page 558
8.2.2 Visual perception in flight control … optical flow and motion parallax......Page 561
8.2.3 Time to contact; optical tau, T......Page 570
8.2.4 T control in the deceleration-to-stop manoeuvre......Page 574
8.2.5 Tau-coupling … a paradigm for safety in action......Page 576
8.2.6 Terrain-following flight in degraded visibility......Page 583
τ on the rising curve......Page 586
8.3 Handling qualities degradation through flight system failures......Page 598
8.3.1 Methodology for quantifying flying qualities following flight function failures......Page 600
Tail rotor failures......Page 602
8.3.3 Malfunction of control … hard-over failures......Page 606
8.3.4 Degradation of control function … actuator rate limiting......Page 612
8.4 Encounters with atmospheric disturbances......Page 614
The wake vortex......Page 616
Hazard severity criteria......Page 617
Analysis of encounters – attitude response......Page 625
Analysis of encounters – vertical response......Page 626
8.4.2 Severity of transient response......Page 631
8.5 Chapter Review......Page 635
Appendix 8A HELIFLIGHT and FLIGHTLAB at the University of Liverpool......Page 637
FLIGHTLAB......Page 639
Immersive cockpit environment......Page 640
References......Page 646
Index......Page 671