The study of flight dynamics requires a thorough understanding of the theory of the stability and control of aircraft, an appreciation of flight control systems and a grounding in the theory of automatic control. Flight Dynamics Principles is a student focused text and provides easy access to all three topics in an integrated modern systems context.
Written for those coming to the subject for the first time, the book provides a secure foundation from which to move on to more advanced topics such as, non-linear flight dynamics, flight simulation, handling qualities and advanced flight control.
About the author:
After graduating Michael Cook joined Elliott Flight Automation as a Systems Engineer and contributed flight control systems design to several major projects. Later he joined the College of Aeronautics to research and teach flight dynamics, experimental flight mechanics and flight control. Previously leader of the Dynamics, Simulation and Control Research Group he is now retired and continues to provide part time support. In 2003 the Group was recognised as the Preferred Academic Capability Partner for Flight Dynamics by BAE SYSTEMS and in 2007 he received a Chairman's Bronze award for his contribution to a joint UAV research programme.
New to this edition:
- Additional examples to illustrate the application of computational procedures using tools such as MATLAB®, MathCad® and Program CC®.
- Improved compatibility with, and more expansive coverage of the North American notational style.
- Expanded coverage of lateral-directional static stability, manoeuvrability, command augmentation and flight in turbulence.
- An additional coursework study on flight control design for an unmanned air vehicle (UAV).
The study of flight dynamics requires a thorough understanding of the theory of the stability and control of aircraft, an appreciation of flight control systems and a grounding in the theory of automatic control. Flight Dynamics Principles is a student focused text and provides easy access to all three topics in an integrated modern systems context. Written for those coming to the subject for the first time, the book provides a secure foundation from which to move on to more advanced topics such as, non-linear flight dynamics, flight simulation, handling qualities and advanced flight control. Additional examples to illustrate the application of computational procedures using tools such as MATLAB(R), MathCad(R) and Program CC(R) Improved compatibility with, and more expansive coverage of the North American notational style Expanded coverage of lateral-directional static stability, manoeuvrability, command augmentation and flight in turbulence An additional coursework study on flight control design for an unmanned air vehicle (UAV)
Front Cover 1
Flight Dynamics Principles 4
Copyright Page 5
Contents 6
Preface 16
Preface to the second edition 18
Preface to the first edition 20
Acknowledgements 22
Nomenclature 24
Subscripts 31
Examples of other symbols and notation 32
1 Introduction 34
1.1 Overview 34
1.2 Flying and handling qualities 36
1.3 General considerations 37
1.3.1 Basic control-response relationships 38
1.3.2 Mathematical models 38
1.3.3 Stability and control 39
1.3.4 Stability and control augmentation 39
1.4 Aircraft equations of motion 39
1.5 Aerodynamics 40
1.5.1 Small perturbations 40
1.6 Computers 41
1.6.1 Analytical computers 41
1.6.2 Flight control computers 41
1.6.3 Computer software tools 42
Matlab 42
Simulink 42
Matlab and Simulink, Student Version Release 14 42
Program CC, Version 5 42
Mathcad 43
20-sim 43
1.7 Summary 43
References 43
Sources 44
2 Systems of Axes and Notation 46
2.1 Earth axes 46
2.2 Aircraft body–fixed axes 47
2.2.1 Generalised body axes 47
2.2.2 Aerodynamic, wind, or stability axes 48
2.2.3 Perturbation variables 48
2.2.4 Angular relationships in symmetric flight 49
2.2.5 Choice of axes 51
2.3 Euler angles and aircraft attitude 52
2.4 Axes transformations 52
2.4.1 Linear quantities transformation 53
2.4.2 Angular velocities transformation 55
2.5 Aircraft reference geometry 58
2.5.1 Wing area 58
2.5.2 Mean aerodynamic chord 59
2.5.3 Standard mean chord 59
2.5.4 Aspect ratio 59
2.5.5 Location of centre of gravity 60
2.5.6 Tail moment arm and tail volume ratio 60
2.5.7 Fin moment arm and fin volume ratio 60
2.6 Controls notation 61
2.6.1 Aerodynamic controls 61
2.6.2 Engine control 61
2.7 Aerodynamic reference centres 62
References 64
Problems 64
3 Static Equilibrium and Trim 66
3.1 Trim equilibrium 66
3.1.1 Preliminary considerations 66
3.1.2 Conditions for stability 67
3.1.3 Degree of longitudinal stability 70
3.1.4 Variation in stability 71
Power effects 71
Other effects 73
3.2 The pitching moment equation 75
3.2.1 Simple development of the pitching moment equation 75
3.2.2 Elevator angle to trim 77
3.2.3 Condition for longitudinal static stability 78
3.3 Longitudinal static stability 78
3.3.1 Controls-fixed stability 78
3.3.2 Controls-free stability 82
3.3.3 Summary of longitudinal static stability 87
3.4 Lateral-directional static stability 88
3.4.1 Lateral static stability 89
3.4.2 Directional static stability 94
3.5 Calculation of aircraft trim condition 96
3.5.1 Defining the trim condition 97
3.5.2 Elevator angle to trim 98
3.5.3 Controls-fixed static stability 99
3.5.4 “AeroTrim”: A Mathcad trim program 100
References 103
Source 103
Problems 103
4 The Equations of Motion 106
4.1 The equations of motion for a rigid symmetric aircraft 106
4.1.1 The components of inertial acceleration 106
4.1.2 The generalised force equations 110
4.1.3 The generalised moment equations 111
4.1.4 Perturbation forces and moments 113
4.2 The linearised equations of motion 113
4.2.1 Gravitational terms 114
4.2.2 Aerodynamic terms 115
4.2.3 Aerodynamic control terms 117
4.2.4 Power terms 117
4.2.5 The equations of motion for small perturbations 118
4.3 The decoupled equations of motion 120
4.3.1 The longitudinal equations of motion 120
4.3.2 The lateral-directional equations of motion 122
4.4 Alternative forms of the equations of motion 123
4.4.1 The dimensionless equations of motion 123
4.4.2 The equations of motion in state space form 126
4.4.3 The equations of motion in American normalised form 132
References 139
Problems 139
5 The Solution of the Equations of Motion 142
5.1 Methods of solution 142
5.2 Cramer’s rule 143
5.3 Aircraft response transfer functions 145
5.3.1 The longitudinal response transfer functions 146
5.3.2 The lateral-directional response transfer functions 148
5.4 Response to controls 150
5.5 Acceleration response transfer functions 154
5.6 The state-space method 156
5.6.1 The transfer function matrix 156
5.6.2 The longitudinal transfer function matrix 158
5.6.3 The lateral-directional transfer function matrix 158
5.6.4 Response in terms of state description 161
Eigenvalues and eigenvectors 162
The modal equations 163
Unforced response 164
Impulse response 165
Step response 165
Response shapes 166
5.7 State-space model augmentation 169
5.7.1 Height response transfer function 170
5.7.2 Incidence and sideslip response transfer functions 171
5.7.3 Flight path angle response transfer function 172
5.7.4 Addition of engine dynamics 172
References 175
Problems 176
6 Longitudinal Dynamics 180
6.1 Response to controls 180
6.1.1 The characteristic equation 185
6.2 The dynamic stability modes 186
6.2.1 The short-period pitching oscillation 186
6.2.2 The phugoid 187
6.3 Reduced-order models 188
6.3.1 The short-period mode approximation 189
6.3.2 The phugoid mode approximation 192
The Lanchester model 192
A reduced-order model 193
6.4 Frequency response 199
6.4.1 The Bode diagram 201
6.4.2 Interpretation of the Bode diagram 203
6.5 Flying and handling qualities 208
6.6 Mode excitation 208
References 212
Problems 212
7 Lateral-Directional Dynamics 216
7.1 Response to controls 216
7.1.1 The characteristic equation 224
7.2 The dynamic stability modes 225
7.2.1 The roll subsidence mode 225
7.2.2 The spiral mode 227
7.2.3 The dutch roll mode 228
7.3 Reduced order models 230
7.3.1 The roll mode approximation 231
7.3.2 The spiral mode approximation 232
7.3.3 The dutch roll mode approximation 233
7.4 Frequency response 237
7.5 Flying and handling qualities 243
7.6 Mode excitation 244
References 248
Problems 248
8 Manoeuvrability 252
8.1 Introduction 252
8.1.1 Manoeuvring flight 252
8.1.2 Stability 253
8.1.3 Aircraft handling 253
8.1.4 The steady symmetric manoeuvre 254
8.2 The steady pull-up manoeuvre 254
8.3 The pitching moment equation 256
8.4 Longitudinal manoeuvre stability 258
8.4.1 Controls-fixed stability 258
8.4.2 Normal acceleration response to elevator 260
8.4.3 Controls-free stability 261
8.4.4 Elevator deflection and stick force 265
8.5 Aircraft dynamics and manoeuvrability 266
8.6 Aircraft with stability augmentation 267
8.6.1 Stick force 268
8.6.2 Stick force per g 268
References 274
9 Stability 276
9.1 Introduction 276
9.1.1 A definition of stability 276
9.1.2 Non-linear systems 276
9.1.3 Static and dynamic stability 277
9.1.4 Control 277
9.2 The characteristic equation 278
9.3 The Routh-Hurwitz stability criterion 279
9.3.1 Special cases 281
9.4 The stability quartic 283
9.4.1 Interpretation of conditional instability 284
9.4.2 Interpretation of the coefficient E 285
9.5 Graphical interpretation of stability 286
9.5.1 Root mapping on the s-plane 286
References 290
Problems 290
10 Flying and Handling Qualities 292
10.1 Introduction 292
10.1.1 Stability 292
10.2 Short term dynamic models 293
10.2.1 Controlled motion and motion cues 293
10.2.2 The longitudinal reduced order model 294
10.2.3 The “thumb print” criterion 299
10.2.4 Incidence lag 300
10.3 Flying qualities requirements 300
10.4 Aircraft role 303
10.4.1 Aircraft classification 303
10.4.2 Flight phase 304
10.4.3 Levels of flying qualities 304
10.4.4 Flight envelopes 304
Permissible flight envelope 304
Service flight envelope 305
Operational flight envelope 305
10.5 Pilot opinion rating 307
10.6 Longitudinal flying qualities requirements 309
10.6.1 Longitudinal static stability 309
10.6.2 Longitudinal dynamic stability 310
Short-period pitching oscillation 310
Phugoid 311
10.6.3 Longitudinal manoeuvrability 312
10.7 Control anticipation parameter 312
10.8 Lateral-directional flying qualities requirements 314
10.8.1 Steady lateral-directional control 314
10.8.2 Lateral-directional dynamic stability 315
Roll subsidence mode 315
Spiral mode 315
Dutch roll mode 316
10.8.3 Lateral-directional manoeuvrability and response 317
10.9 Flying qualities requirements on the s-plane 317
10.9.1 Longitudinal modes 318
10.9.2 Lateral-directional modes 319
References 323
Problems 323
11 Command and Stability Augmentation 326
11.1 Introduction 326
11.1.1 The control law 328
11.1.2 Safety 328
11.1.3 Stability augmentation system architecture 329
11.1.4 Scope 332
11.2 Augmentation system design 332
11.3 Closed-loop system analysis 335
11.4 The root locus plot 339
11.5 Longitudinal stability augmentation 345
11.6 Lateral-directional stability augmentation 352
11.7 The pole placement method 363
11.8 Command augmentation 368
11.8.1 Command path filter design 369
11.8.2 The frequency response of a phase compensation filter 371
11.8.3 Introduction of a command path filter to the system state model 372
References 381
Problems 381
12 Aerodynamic Modelling 386
12.1 Introduction 386
12.2 Quasi-static derivatives 387
12.3 Derivative estimation 389
12.3.1 Calculation 390
12.3.2 Wind tunnel measurement 390
12.3.3 Flight test measurement 391
12.4 The effects of compressibility 393
12.4.1 Some useful definitions 393
12.4.2 Aerodynamic models 394
12.4.3 Subsonic lift, drag, and pitching moment 395
12.4.4 Supersonic lift, drag, and pitching moment 396
12.4.5 Summary 397
12.5 Limitations of aerodynamic modelling 401
References 401
13 Aerodynamic Stability and Control Derivatives 404
13.1 Introduction 404
13.2 Longitudinal aerodynamic stability derivatives 404
13.2.1 Preliminary considerations 404
13.2.2 Aerodynamic force and moment components 406
13.2.3 Force derivatives due to velocity perturbations 406
Xu =.X/.U Axial force due to axial velocity 406
Zu =.Z/.U Normal force due to axial velocity 407
Xw =.X/.W Axial force due to normal velocity 408
Zw =.Z/.W Normal force due to normal velocity 408
13.2.4 Moment derivatives due to velocity perturbations 409
Mu =.M/.U Pitching moment due to axial velocity 409
Mw =.M/.W Pitching moment due to normal velocity 410
13.2.5 Derivatives due to a pitch velocity perturbation 410
Xq =.X/.q Axial force due to pitch rate 411
Zq =.Z/.q Normal force due to pitch rate 412
Mq =.M/.q Pitching moment due to pitch rate 412
13.2.6 Derivatives due to acceleration perturbations 413
Xw =.X/.w Axial force due to rate of change of normal velocity 415
Zw=.Z/.w Normal force due to rate of change of normal velocity 416
Mw =.M/.w Pitching moment due to rate of change of normal velocity 416
13.3 Lateral-directional aerodynamic stability derivatives 417
13.3.1 Preliminary considerations 417
13.3.2 Derivatives due to sideslip 417
Yv =.Y/.V Sideforce due to sideslip 418
Lv =.L/.V Rolling moment due to sideslip 419
Nv =.N/.V Yawing moment due to sideslip 426
13.3.3 Derivatives due to rate of roll 427
Yp =.Y/.p Sideforce due to roll rate 427
Lp =.L/.p Rolling moment due to roll rate 428
Np =.N/.p Yawing moment due to roll rate 430
13.3.4 Derivatives due to rate of yaw 431
Yr =.Y/.r Sideforce due to yaw rate 432
Lr =.L/.r Rolling moment due to yaw rate 433
Nr =.N/.r Yawing moment due to yaw rate 436
13.4 Aerodynamic control derivatives 437
13.4.1 Derivatives due to elevator 438
X. =.X/.. Axial force due to elevator 438
Z. =.Z/.. Normal force due to elevator 439
M. =.M/.. Pitching moment due to elevator 439
13.4.2 Derivatives due to aileron 439
Y. =.Y/.. Sideforce due to aileron 440
L. =.L/.. Rolling moment due to aileron 441
N. =.N/.. Yawing moment due to aileron 441
13.4.3 Derivatives due to rudder 442
Y. =.Y/.. Sideforce due to rudder 442
L. =.L/.. Rolling moment due to rudder 443
N. =.N/.. Yawing moment due to rudder 443
13.5 North American derivative coefficient notation 443
13.5.1 The longitudinal aerodynamic derivative coefficients 445
13.5.2 The lateral-directional aerodynamic derivative coefficients 449
13.5.3 Comments 451
References 468
Problems 468
14 Flight in a Non-steady Atmosphere 474
14.1 The influence of atmospheric disturbances on flying qualities 474
14.2 Methods of evaluation 475
14.3 Atmospheric disturbances 476
14.3.1 Steady wind 476
14.3.2 Wind shear 477
14.3.3 Discrete gusts 477
14.3.4 Continuous turbulence 477
14.4 Extension of the linear aircraft equations of motion 479
14.4.1 Disturbed body incidence and sideslip 480
14.4.2 The longitudinal equations of motion 481
14.4.3 The lateral-directional equations of motion 483
14.4.4 The equations of motion for aircraft with stability augmentation 484
14.5 Turbulence modelling 489
14.5.1 The von Kármán model 490
14.5.2 The Dryden model 490
14.5.3 Comparison of the von Kármán and Dryden models 492
14.5.4 Turbulence scale length 492
14.5.5 Turbulence intensity 494
14.6 Discrete gusts 495
14.6.1 The “1-cosine” gust 495
14.6.2 Determination of maximum gust velocity and horizontal length 497
14.7 Aircraft response to gusts and turbulence 498
14.7.1 Variance, power spectral density, and white noise 498
14.7.2 Spatial and temporal equivalence 500
14.7.3 Synthetic turbulence 501
14.7.4 Aircraft response to gusts 503
14.7.5 Aircraft response to turbulence 505
References 517
15 Coursework Studies 520
15.1 Introduction 520
15.1.1 Working the assignments 520
15.1.2 Reporting 520
15.2 Assignment 1: Stability augmentation of the North American X-15 hypersonic research aeroplane 521
15.2.1 The aircraft model 521
15.2.2 The solution tasks 521
15.3 Assignment 2: The stability and control characteristics of a civil transport aeroplane with relaxed longitudinal stati... 522
15.3.1 The aircraft model 522
15.3.2 The governing trim equations 524
15.3.3 Basic aircraft stability and control analysis 524
15.3.4 Relaxing the stability of the aircraft 525
15.3.5 Relaxed stability aircraft stability and control analysis 525
15.3.6 Evaluation of results 525
15.3.7 Postscript 525
15.4 Assignment 3: Lateral-directional handling qualities design for the Lockheed F-104 Starfighter aircraft 525
15.4.1 The aircraft model 526
15.4.2 Lateral-directional autostabiliser structure 527
15.4.3 Basic aircraft stability and control analysis 527
15.4.4 Augmenting the stability of the aircraft 528
15.4.5 Inclusion of the washout filter in the model 530
15.4.6 Designing the aileron-rudder interlink gain 530
15.5 Assignment 4: Analysis of the effects of Mach number on the longitudinal stability and control characteristics of the ... 531
15.5.1 The aircraft model 531
15.5.2 The assignment tasks 531
Assembling the derivatives 531
Solving the equations of motion 531
Assessing the dynamic stability characteristics 531
Stability augmentation 532
Assessing the effects of Mach number 532
15.6 Assignment 5: The design of a longitudinal primary flight control system for an advanced-technology UAV 534
15.6.1 The aircraft model 534
15.6.2 The design requirements 536
15.6.3 The assignment tasks 537
Solving the equations of motion 537
Designing the speed control loop 537
Assessing the performance of the speed controller 537
Re-arranging the system state model with speed loop closed 537
Designing the pitch rate control loop 538
Designing the pitch attitude control loop 538
Assessing the performance of the pitch attitude controller 538
References 538
Appendix 1: AeroTrim: A Symmetric Trim Calculator for Subsonic Flight Conditions 540
1. Aircraft Flight Condition 540
2. Air Density Calculation 540
3. Set up Velocity Range for Computations 540
4. Aircraft Geometry—Constant 541
5. Wing-Body Aerodynamics 541
6. Tailplane Aerodynamics 542
7. Wing and Tailplane Calculations 542
8. Downwash at Tail 542
9. Induced Drag Factor 542
10. Basic Performance Parameters 543
11. Trim Calculation 543
12. Trim Variables Calculation 544
13. Conversions of Angles to Degrees 544
14. Total Trim Forces Acting on Aircraft 544
Summary Results of Trim Calculation 545
15. Definition of Flight Condition 545
16. Trim Conditions as a Function of Aircraft Velocity 545
17. Some Useful Trim Plots 546
Appendix 2: Definitions of Aerodynamic Stability and Control Derivatives 548
A2.1 Notes 548
Appendix 3: Aircraft Response Transfer Functions Referred to Aircraft Body Axes 556
A3.1 Longitudinal Response Transfer Functions in Terms of Dimensional Derivatives 556
A3.2 Lateral-Directional Response Transfer Functions in Terms of Dimensional Derivatives 558
A3.3 Longitudinal Response Transfer Functions in Terms of Concise Derivatives 559
A3.4 Lateral-Directional Response Transfer Functions in Terms of Concise Derivatives 560
Appendix 4: Units, Conversions, and Constants 562
Appendix 5: A Very Short Table of Laplace Transforms 564
Appendix 6: The Dynamics of a Linear Second Order System 566
Appendix 7: North American Aerodynamic Derivative Notation 570
Appendix 8: Approximate Expressions for the Dimensionless Aerodynamic Stability and Control Derivatives 572
Appendix 9: Transformation of Aerodynamic Stability Derivatives from a Body Axes Reference to a Wind Axes Reference 576
A9.1 Introduction 576
A9.2 Force and Moment Transformation 576
A9.3 Aerodynamic Stability Derivative Transformations 577
A9.3.1 Force-Velocity Derivatives 577
A9.3.2 Moment-Velocity Derivatives 578
A9.3.3 Force-Rotary Derivatives 578
A9.3.4 Moment-Rotary Derivatives 579
A9.3.5 Force-Acceleration Derivatives 580
A9.3.6 Moment-Acceleration Derivatives 581
A9.3.7 Aerodynamic Control Derivatives 581
A9.4 Summary 582
Appendix 10: Transformation of the Moments and Products of Inertia from a Body Axes Reference to a Wind Axes Reference 586
A10.1 Introduction 586
A10.2 Coordinate Transformation 586
A10.2.1 Body Axes to Wind Axes 586
A10.2.2 Wind Axes to Body Axes 587
A10.3 Transformation of the Moment of Inertia in Roll from a Body Axes Reference to a Wind Axes Reference 587
A10.4 Summary 588
Appendix 11: The Root Locus Plot 590
A11.1 Mathematical Background 590
A11.2. Rules for Constructing a Root Locus Plot 591
Rule 1 592
Rule 2 592
Rule 3 592
Rule 4 592
Rule 5 592
Method 1 593
Method 2 593
Rule 6 593
Rule 7 593
Rule 8 593
Index 596
Chapter 1
Introduction
1.1 Overview
This book is primarily concerned with the provision of good flying and handling qualities in conventional piloted aircraft, although the material is equally applicable to uninhabited air vehicles (UAV). Consequently, it is also very much concerned with the stability, control, and dynamic characteristics which are fundamental to the determination of those qualities. Since flying and handling qualities are of critical importance to safety and to the piloting task, it is essential that their origins are properly understood. Here, then, the intention is to set out the basic principles of the subject at an introductory level and to illustrate the application of those principles by means of worked examples.
Following the first flights made by the Wright brothers in December 1903, the pace of aeronautical development quickened and the progress made in the following decade or so was dramatic. However, the stability and control problems that faced early aviators were sometimes considerable since the flying qualities of their aircraft were often less than satisfactory. Many investigators were studying the problems of stability and control at the time, although it is the published works of Bryan (1911) and Lanchester (1908) which are usually credited with laying the first really secure foundations for the subject. By conducting many experiments with flying models, Lanchester was able to observe and successfully describe mathematically some dynamic characteristics of aircraft. The beauty of Lanchester’s work was its practicality and theoretical simplicity, which facilitates easy application and interpretation. Bryan, on the other hand, was a mathematician who chose to apply his energies, with the assistance of a Mr. Harper, to the problems of aircraft stability and control. He developed the general equations of motion of a rigid body with six degrees of freedom to successfully describe aircraft motion. His treatment, with very few changes, is still in everyday use. What has changed is the way in which the material is now used, due largely to the advent of the digital computer as an analysis tool. Together, the stability and control of aircraft is a subject which has its origins in aerodynamics, and the classical theory of the subject is traditionally expressed in the language of the aerodynamicist. However, most advanced-technology aircraft may be described as an integrated system comprising airframe, propulsion, flight controls, and so on. It is therefore convenient and efficient to utilise powerful computational systems engineering tools to analyse and describe the system’s flight dynamics. Thus, the objective of the present work is to revisit the development of the classical theory and to express it in the language of the systems engineer where it is more appropriate to do so.
The subject of flight dynamics is concerned with the relatively short-term motion of aircraft in response to controls or to external disturbances such as atmospheric turbulence. The motion of interest can vary from small excursions about trim to very-large-amplitude manoeuvring when normal aerodynamic behaviour may well become very non-linear. Since the treatment of the subject is introductory, a discussion of large-amplitude dynamics is beyond the scope of the present work.
The dynamic behaviour of an aircraft is shaped significantly by its stability and control properties, which in turn have their roots in the aerodynamics of the airframe. Previously the achievement of aircraft with good stability characteristics usually ensured good flying qualities, all of which depended only on good aerodynamic design. Expanding flight envelopes and the increasing dependence on an automatic flight control system (AFCS) for stability augmentation means that good flying qualities are no longer a guaranteed product of good aerodynamic design and good stabilitycharacteristics. The reasons for this apparent inconsistency are now reasonably well understood and, put very simply, result from the addition of flight control system dynamics to those of the airframe. Flight control system dynamics are of course a necessary, but not always desirable, by-product of command and stability augmentation.
Modern flight dynamics is concerned not only with the dynamics, stability, and control of the basic airframe but also with the sometimes complex interaction between the airframe and flight control system. Since the flight control system comprises motion sensors, a control computer, control actuators, and other essential items of control hardware, a study of the subject becomes a multidisciplinary activity. Therefore, it is essential that the modern flight dynamicist has not only a thorough understanding of the classical stability and control theory of aircraft but also a working knowledge of control theory and of the use of computers in flight-critical applications. Modern aircraft comprise the airframe together with the flight control equipment and may be treated as a whole system using the traditional tools of the aerodynamicist and the analytical tools of the control engineer.
Thus in a modern approach to the analysis of stability and control, it is convenient to treat the airframe as a system component. This leads to the derivation of mathematical models which describe aircraft in terms of aerodynamic transfer functions. Described in this way, the stability, control, and dynamic characteristics of aircraft are readily interpreted with the aid of very powerful computational systems engineering tools. It follows that the mathematical model of the aircraft is immediately compatible with, and provides the foundation for integration with, flight control system studies. This is an ideal state of affairs since today it is commonplace to undertake stability and control investigations as a precursor to flight control system development.
The modern flight dynamicist tends to be concerned with the wider issues of flying and handling qualities rather than with the traditional, and more limited, issues of stability and control. The former are, of course, largely determined by the latter. The present treatment of the material is shaped by answering the following questions which a newcomer to the subject might be tempted to ask:
How are the stability and control characteristics of aircraft determined, and how do they influence flying qualities?
The answer to this question involves the establishment of a suitable mathematical framework for the problem, the development of the equations of motion and their solution, investigation of response to controls, and the general interpretation of dynamic behaviour.
What are acceptable flying qualities; how are the requirements defined, interpreted, and applied; and how do they limit flight characteristics?
The answer to this question involves a review of contemporary flying qualities requirements and their evaluation and interpretation in the context of stability and control characteristics.
When an aircraft has unacceptable flying qualities, how may its dynamic characteristics be improved?
The answer to this question involves an introduction to the rudiments of feedback control as the means of augmenting the stability of the basic airframe.
1.2 Flying and handling qualities
The flying and handling qualities of an aircraft are those properties which describe the ease and effectiveness with which the aircraft responds to pilot commands in the execution of a flight task, or mission task element (MTE). In the first instance, therefore, flying and handling qualities are described qualitatively and are formulated in terms of pilot opinion; consequently, they tend to be rather subjective. The process involved in pilot perception of flying and handling qualities may be interpreted in the form of a signal flow diagram, as shown in Fig. 1.1. The solid lines represent physical, mechanical or electrical signal flow paths; the dashed lines represent sensory feedback information to the pilot. The author’s interpretation distinguishes between flying qualities and handling qualities as indicated. The pilot’s perception of flying qualities is considered to be a qualitative description of how well the aeroplane carries out the commanded task. On the other hand, the pilot’s perception of handling qualities is considered to be a qualitative description of the adequacy of the short-term dynamic response to controls in the execution of the flight task. The two qualities are therefore very much interdependent and in practice are probably inseparable. To summarise, then, flying qualities may be regarded as being task-related whereas the handling qualities may be regarded as being response-related. When the airframe characteristics are augmented by a flight control system, the way in which that system may influence the flying and handling qualities is clearly shown in Fig. 1.1.
Figure 1.1 Flying and handling qualities of conventional aircraft.
Most advanced modern aeroplanes employ fly-by-wire (FBW) primary flight controls, and these are usually integrated with the stability augmentation system. In this case, the interpretation of flying and handling qualities is modified to that shown in Fig. 1.2. Here the flight control system becomes an integral part of the primary signal flow path, and the influence of its dynamic characteristics on flying and handling qualities is of critical importance. The need for very careful...
| Erscheint lt. Verlag | 3.10.2012 |
|---|---|
| Sprache | englisch |
| Themenwelt | Natur / Technik ► Fahrzeuge / Flugzeuge / Schiffe ► Luftfahrt / Raumfahrt |
| Technik ► Fahrzeugbau / Schiffbau | |
| Technik ► Luft- / Raumfahrttechnik | |
| Technik ► Maschinenbau | |
| Wirtschaft | |
| ISBN-10 | 0-08-098276-X / 008098276X |
| ISBN-13 | 978-0-08-098276-2 / 9780080982762 |
| Haben Sie eine Frage zum Produkt? |
PDF (Adobe DRM)Größe: 11,2 MB
Kopierschutz: Adobe-DRM
Adobe-DRM ist ein Kopierschutz, der das eBook vor Mißbrauch schützen soll. Dabei wird das eBook bereits beim Download auf Ihre persönliche Adobe-ID autorisiert. Lesen können Sie das eBook dann nur auf den Geräten, welche ebenfalls auf Ihre Adobe-ID registriert sind.
Details zum Adobe-DRM
Dateiformat: PDF (Portable Document Format)
Mit einem festen Seitenlayout eignet sich die PDF besonders für Fachbücher mit Spalten, Tabellen und Abbildungen. Eine PDF kann auf fast allen Geräten angezeigt werden, ist aber für kleine Displays (Smartphone, eReader) nur eingeschränkt geeignet.
Systemvoraussetzungen:
PC/Mac: Mit einem PC oder Mac können Sie dieses eBook lesen. Sie benötigen eine
eReader: Dieses eBook kann mit (fast) allen eBook-Readern gelesen werden. Mit dem amazon-Kindle ist es aber nicht kompatibel.
Smartphone/Tablet: Egal ob Apple oder Android, dieses eBook können Sie lesen. Sie benötigen eine
Geräteliste und zusätzliche Hinweise
Buying eBooks from abroad
For tax law reasons we can sell eBooks just within Germany and Switzerland. Regrettably we cannot fulfill eBook-orders from other countries.
EPUB (Adobe DRM)Größe: 16,2 MB
Kopierschutz: Adobe-DRM
Adobe-DRM ist ein Kopierschutz, der das eBook vor Mißbrauch schützen soll. Dabei wird das eBook bereits beim Download auf Ihre persönliche Adobe-ID autorisiert. Lesen können Sie das eBook dann nur auf den Geräten, welche ebenfalls auf Ihre Adobe-ID registriert sind.
Details zum Adobe-DRM
Dateiformat: EPUB (Electronic Publication)
EPUB ist ein offener Standard für eBooks und eignet sich besonders zur Darstellung von Belletristik und Sachbüchern. Der Fließtext wird dynamisch an die Display- und Schriftgröße angepasst. Auch für mobile Lesegeräte ist EPUB daher gut geeignet.
Systemvoraussetzungen:
PC/Mac: Mit einem PC oder Mac können Sie dieses eBook lesen. Sie benötigen eine
eReader: Dieses eBook kann mit (fast) allen eBook-Readern gelesen werden. Mit dem amazon-Kindle ist es aber nicht kompatibel.
Smartphone/Tablet: Egal ob Apple oder Android, dieses eBook können Sie lesen. Sie benötigen eine
Geräteliste und zusätzliche Hinweise
Buying eBooks from abroad
For tax law reasons we can sell eBooks just within Germany and Switzerland. Regrettably we cannot fulfill eBook-orders from other countries.
aus dem Bereich
