Table Of ContentSynthesis of Subsonic Aitplane Design
Synthesis of Subsonic
Airplane Design
An introduction to the preliminary design of subsonic
general aviation and transport aircraft, with emphasis on
layout, aerodynamic design, propulsion and performance
Egbert Torenbeek
with a foreword by
H. Wittenberg
1982
fi
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
Library of Congress Cataloging in Publication Data CIP
Torenbeek, Egbert.
Synthesis of Subsonic Aiiplane Design.
Includes bibliographical references and index.
1. Airplanes-Design and Construction.
I. Title.
TL671.2.T67 1982 629.134'1 82-12469
ISBN 978-90-481-8273-2 ISBN 978-94-017-3202-4 (eBook)
DOI 10.1007/978-94-017-3202-4
Reprinted 1984,1985,1987,1988,1990,1993, 1995, 1996.
Copyright© 1982 by Springer Science+Business Media Dordrecht
Originally published by Kluwer Academic Publishers in 1982
All rights reserved. No palt of this publication may be reproduced, stored in a retrieval system,
or transmitted in any form or by any means, mechanical, photocopying, recording, or
otherwise, without written permission of the copyright owner,
Springer-Science+Business Media, B.V.
Contents
page
FOREWORD
by Professor H. Wittenberg xvi
AUTHOR'S PREFACE xviii
ACKNOWLEDGE11ENTS xix
UNITS xxi
CHAPTER 1. GENERAL ASPECTS OF AIRCRAFT CONFIGURATION DEVELOPMENT
1.1. Introduction
2
1.2. Aircraft design and development
3
1.3. Configuration development
5
1.3.1. The design concept
6
1.3.2. Initial configuration design and configuration variations 7
1.3.3. Baseline configuration development
8
1.3.4. The preliminary design department
9
1.4. The initial specification
10
1.4.1. The need for a new type of aircraft 10
1.4.2. Transport capacity
12
1.4.3. Design cruising speed and range 13
1.4.4. Low-speed characteristics and field performance 14
1.4.5. Other requirements 15
1.5. A continuous thread running through the design process 16
1.5.1. The iterative character of design
16
1.5.2. Searching for the optimum
17
1.5.3. A suggested scheme for preliminary design 18
1.6. Impact of civil airworthiness requirements, and operating and flight rules 19
1.6.1. General
19
1.6.2. Federal Aviation Regulations
21
1.6.3. British Civil Airworthiness Requirements 22
1.6.4. Airworthiness standards and desig~ 23
1.7. Conclusion
25
CHAPTER 2. THE GENERAL ARRANGEMENT
27
2.1. Introduction 28
v
page
2. 2. Hj_gh , low or mid wing? 30
2. 2. 1. High wing 34
2.2.2. Mid win9 36
2.2.3. Low wing 37
2.2.4. Effects of wing location on the general arrangement 37
2.3. Location of the engines 39
2.3.1. Propeller aircraft 39
2.3.2. Jet-propelled transport aircraft 41
2.3.3. Single-engine subsonic jet aircraft 46
2.4. Arrangement of the tailplane 50
2.4.1. Classification of tail surface configurations 50
2.4.2. The location of tail surfaces 51
2.5. Arrangement of the undercarriage 54
2.5.1. Tailwheel undercarriage 54
2.5.2. Nosewheel undercarriage 54
2.5.3. Tandem undercarriage 55
2 •. 6. Some unconventional aircraft configurations 55
2.6.1. The flying wing 56
2.6.2. Tailless aircraft 58
2.6.3. Tail-first (or canard) layout 58
CHAPTER 3. FUSELAGE DESIGN 61
3.1. Introduction 62
3.1.1. Function and design requirements 62
3.1.2. Drag and optimization of the external shape 63
3. 1. 3. A design procedure for fuselages with cylindrical mid-se.ction 67
3.2. The fuselage of airliners and general aviation aircraft 68
3.2.1. Importance of comfort and payload density 68
3.2.2. Cabin design 69
3.2.3. Passenger seats 75
3.2.4. Passenger emergency exits, doors and windows 76
3.2.5. Cargo holds 78
3.2.6. Services 79
3.3. The fuselage of cargo aircraft 81
3.3.1. The case for the civil freighter 81
3. 3. 2. Payload density and volume of. the freight hold 83
3.3.3. Loading systems 84
3.3.4. Accessibility of the freight hold 84
3.4. Flight deck design 88
3.4.1. Location of the pilot's seat and the flight controls 88
3.4.2. Visibility from the cockpit 90
3.4.3. Flight deck dimensions and layout 92
3.4.4. Emergency exits for crew members 94
3.5. Some remarks concerning the external shape 94
3.5.1. Fuselages with a cylindrical mid-section 94
3.5.2. Fuselages for relatively small useful loads 95
VI
page
CHAPTER 4. AN APPRECIATION OF SUBSONIC ENGINE TECHNOLOGY 97
4.1. Introductory comparison of engine types 99
4.2. Current reciprocating engines 101
4.2.1. Some characteristics of the four stroke engine 101
4.2.2. Engine design and its influence on flight performance 106
4.2.3. Engine classification by cylinder arrangement 110
4.2.4. Two-stroke and Rotary Combustion engines 111
4.3. Basic properties of aircraft gas turbines for subsonic speeds 112
4.3.1. The gas producer 113
4.3.2. The propulsive device 116
4.3.3. The pure jet engine 116
4.3.4. The turbofan engine 116
4.3.5. The turboprop engine 117
4.3.6. Overall efficiency, specific fuel consumption and specific thrust
(power) 118
4.3.7. Analysis of the engine cycle 119
4.4. Assessment of turbojet engines 120
4.4 .1. Overall Pressure Ratio 121
4. 4. 2. Turbine Entry Temperature 123
4. 4. 3. Bypass ratio 125
4. 4. 4. Engine noise 131
4.4.5. Summary and prognosis for the turbofan engine 133
4.4.6.tEngine performance in non-standard atmosphere 133
4.5. Assessment of turboprop engines 134
4.5.1. Performance 135
4.5.2. Weight and drag 137
4.5.3. Turboprop engine configurations 137
CHAPTER 5. DESIGN FOR PERFORMANCE 141
5.1. Introduction 143
5.2. Initial weight prediction 144
5.2.1. Stages in the estimation of airplane weight 144
5.2.2. Examples of weight "guesstimates11 145
5.3. Initial estimation of airplane drag 148
5.3.1. Drag breakdown 148
5.3.2. Low-speed drag estimation method 14 9
5.3.3. Compressibility drag 152
5.3.4. Retracing a drag polar from performance figures 153
5.3.5. Drag in takeoff and landing 153
5.4. Evaluation of performance requirements 155
5.4.1. High-speed performance 155
5.4.2. Range performance
157
5.4.3. Climb performance
160
5.4.4. Stalling and minimum flight speeds 165
5.4.5. Takeoff 167
5.4.6. Landing
170
VII
page
5.5. Aircraft synthesis and optimization 171
5.5.1. Purpose of parametric studies 171
5.5.2. Basic rules 172
5.5.3. Sizing the wing of a long-range passenger transport 173
5.5.4. Wing loading and thrust (power) loading diagrams 174
5.5.5. Optimization for low operating costs 178
5.5.6. Community noise considerations 178
CHAPTER 6. CHOICE OF THE ENGINE AND PROPELLER AND INSTALLATION OF THE POWERPLANT 181
6.1. Introduction 182
6.2. Choice of the number of engines and the engine type 183
6.2.1. Engine installation factors 183
6.2.2. Engine failure 184
6.2.3. Engine performance and weight variations 186
6.2.4. Choice of the engine type 187
6.3. Characteristics, choice and installation of propellers 190
6.3.1. General aspects 190
6.3.2. Propeller coefficients and diagrams 191
6.3.3. Blade angle control 195
6.3.4. Propeller geometry 199
6.4. Installation of propeller engines 204
6.4.1. Location of the propellers 204
6.4.2. Tractor engines in the nose of the fuselage 205
6.4.3. Wing-mounted tractor engines 205
6.5. Installation of turbojet engines 206
6.5.1. General reqUirements 206
6.5.2. Fuselage-mounted podded engines 207
6.5.3. Wing-mounted podded engines 209
6.6. Miscellaneous aspects of powerplant installation 210
6.6.1. Thrust reversal 210
6.6.2. Auxiliary Power Units (APU) 213
CHAPTER 7. AN INTRODUCTION TO WING DESIGN 215
7.1. Introduction and general design requirements 217
7.2. Wing area 219
7.2.1. Wing loading for optimum cruising conditions 219
7.2.2. Wing loading limits and structural aspects 224
7.3. Some considerations on low-speed stalling 227
7.3.1. Stall handling requirements and stall warning 227
7. 3.2. Design for adequate stall chaz·acteristics 228
7. 3. 3'. Stalling properties of airfoil sections 229
7. 3. '4. Spanwise progression of the stall 231
7.4. Wing design for low-subsonic aircraft 232
7.4.1. Planform 232
7.4.2. Aspect ratio 233
7.4.3. Thickness ratio 235
VIII
page
7.4.4. Wing taper 236
7.4.5. Airfoil selection 237
7.4.6. Stalling characteristics and wing twist 239
7.5. Wing design for high-subsonic aircraft 241
7.5.1. Wing sections at high-subsonic speeds 241
7.5.2. Wing design for high speeds 246
7.5.3. Low-speed problems of high-speed wings 249
7.5.4. Planform selection 251
7.6. High lift and flight control devices 252
7.6.1. General considerations 252
7.6.2. Trailing-edge flaps 253
7.6.3. Leading-edge high lift devices 256
7.6.4. Flight control devices 257
7.7. Dihedral, anhedral and wing setting 258
7.7.1. The angle of dihedral (anhedral) 258
7.7.2. Wing/body incidence 259
7.8. The wing structure 259
7.8.1. Types of wing structure
259
7.8.2. Structural arrangement in plan 261
CHAPTER 8. AIRPLANE WEIGHT AND BALANCE 263
8.1. Introduction; the importance of low weight 265
8.2. Weight subdivision and limitations 268
8.2.1. Weight subdivision 269
8.2.2. Weight limitations and capacities 271
8.2.3. Operational weights and the payload-range diagram 273
8.2.4. The choice of weight limits 274
8.3. Methodology of empty weight prediction 275
8.4. Weight prediction data and methods 277
8.4.1. Airframe structure 277
8.4.2. The propulsion group 285
8.4.3. Airframe services and equipment 286
8.4.4. Useful Load and the All-Up Weight 293
8.5. Center of gravity 294
8.5.1. The load and balance diagram 296
8. 5. 2. Loading flexibility and res.trictions 297
8.5.3. Effects of the general arrangement and ·layout 299
8.5.4. Design procedure to obtain a balanced aircraft 300
CHAPTER 9. PRELIMINARY TAILPLANE DESIGN 303
9.1. Introduction to tailplane design, control systems and stabilization 305
9.2. Static longitudinal stability and elevator control forces 308
9.2.1. Stick-fixed static stability and neutral point 308
9.2.2. Stick-free static stability and neutral point; the stick force
gradient 310
9.2.3. Stick-fixed and stick-free maneuver points and maneuver control 311
IX
page
forces
9.2.4. Reduction of control forces 313
9.2.5. Effects of compressibility and powerplant operation 316
9.3. Some aspects of dynamic behavior 317
9.3.1. Characteristics of the SP oscillation 317
9.3.2. Criteria for acceptable SP characteristics 319
9.3.3. A simple criterion for the tailplane size 320
9.3.4. The phugoid 323
9.4. Longitudinal control at low speeds 323
9.4.1. Control capacity required to stall the aircraft 324
9.4.2. Control capacity required for takeoff rotation and landing flareout 325
9.4.3. Out-of-trim conditions 326
9.5. Preliminary design of the horizontal tailplane 326
9.5.1. Tailplane shape and configuration 326
9.5.2. Design procedures 321
9.6. Design of the vertical tailplane 331
9.6.1. Control after engine failure: multi-engine aircraft 332
9.6.2. Lateral stability 335
9.6.3. Crosswind landings 338
9.6.4. The spin 338
9.6.5. Preliminary design of the vertical tailplane 339
CHAPTER 10. THE UNDERCARRIAGE LAYOUT 341
10.1. Introduction 342
10.2. Tailoring the undercarriage to the bearing capacity of airfields 343
10.2.1. Runway classification 343
10.2.2. The Equivalent Single Wheel Load (ESWL) 345
10.2.3. Multiple wheel undercarriage configurations 348
10.3. Disposition of the wheels 349
10.3.1. Angles of pitch and roll during takeoff and landing 349
10.3.2. Stability at touchdown and during taxying: tricycle under-
carriages 351
10.3.3. Gear length, wheelbase and track: tricycle undercarriages 353
10.3.4. Disposition of a tailwheel undercarriage 355
10.4. Type, size and inflation pressure of the tires 356
10.4.1. Main wheel tires 356
10.4.2. Nosewheel tires 358
10.4.3. Inflation pressure 359
10.5. Gear geometry and retraction 360
10.5.1. Energy absorption on touchdown 360
10.5.2. Dimensions of the gear 361
10.5.3. Gear retraction 362
CHAPTER 11. ANALYSIS OF AERODYNAMIC AND OPERATIONAL CHARACTERISTICS 365
11.1. Introduction 366
11.2. Terminology in relation to the determination of drag 368
X
