v

CHAPTER 1 Market Survey and Mission Specification ���������������� 1 1�1 A growing market for commercial aircraft .....................................1 1�2 Technology drivers ..........................................................................6 1�2�1 Fuel efficiency .....................................................................7 1�2�2 Weight reduction ..................................................................9 1�2�3 Drag reduction ...................................................................10 1�2�4 Engine design ....................................................................10 1�2�5 Carbon footprint ................................................................11 1�2�6 Biofuels ..............................................................................12 1�2�7 Alternative fuels and power sources ..................................13 1�2�8 Noise and vibration ............................................................13 1�3 Cargo aircraft ................................................................................16 1�4 Design summary ...........................................................................17 1�4�1 Mission specification .........................................................17 1�4�2 The market survey .............................................................17

References .....................................................................................20

CHAPTER 2 Preliminary Weight Estimation ������������������������������ 21 2�1 The mission specification .............................................................21 2�2 The mission profile .......................................................................22 2�3 Weight components .......................................................................24 2�3�1 Gross, takeoff, and operating empty weights ....................24 2�3�2 Passenger and crew weights ..............................................24 2�3�3 Cargo weight ......................................................................26 2�3�4 Fuel weight ........................................................................26 2�3�5 Fuel consumption by mission segment ..............................29 2�3�6 Fuel consumption in segments other than cruise ...............29 2�3�7 Fuel consumption in cruise ................................................31 2�3�8 Selection of cruise performance characteristics ................32 2�4 Empty weight trends .....................................................................34 2�5 Fuel characteristics .......................................................................36 2�6 Estimation of the takeoff and empty weights ...............................38 2�6�1 New materials for weight reduction ..................................39 2�7 Weight estimation for turboprop-powered aircraft .......................39 2�7�1 Fuel weight estimation for turboprop airliners ..................40 2�7�2 Empty weight estimation for turboprop airliners ..............40

Contents

Preface ......................................................................................................................xvIntroduction ............................................................................................................xvii

vi Contents

2�8 Design summary ...........................................................................42 2�9 Nomenclature ................................................................................44 2�9�1 Subscript ............................................................................44

References .....................................................................................44

CHAPTER 3 Fuselage Design ��������������������������������������������������� 47 3�1 Introduction ...................................................................................47 3�2 Commercial aircraft cabin volume and pressure ..........................48 3�2�1 Cabin volume .....................................................................49 3�2�2 Cabin pressure ...................................................................51 3�3 General cabin layout .....................................................................52 3�4 Cabin cross-section .......................................................................53 3�5 Estimation of fuselage width ........................................................56 3�6 Estimation of fuselage length .......................................................57 3�7 Influence of fuselage fineness ratio ...............................................60 3�7�1 Fuselage effects on drag ....................................................60 3�7�2 Fuselage effect on lift ........................................................64 3�8 Estimation of nose cone and tail cone length ...............................65 3�9 Cargo containers ...........................................................................66 3�10 Emergency exits ............................................................................68 3�11 Recent developments in fuselage design ......................................70 3�12 Design summary ...........................................................................75 3�13 Nomenclature ................................................................................78 3�13�1 Subscripts .........................................................................78

References .....................................................................................79

CHAPTER 4 Engine Selection �������������������������������������������������� 81 4�1 Introduction ...................................................................................81 4�2 Landing requirements ...................................................................82 4�3 Wing loading in landing................................................................84 4�4 Landing field length ......................................................................85 4�5 Wing loading in takeoff ................................................................87 4�6 Takeoff distance ............................................................................90 4�7 Cruise requirements ......................................................................95 4�8 Construction of the engine selection design chart ........................96 4�9 Flight test data for landing and power approach ...........................99 4�10 Turbojet and turbofan engines ....................................................101 4�10�1 Dual shaft turbojet ..........................................................101 4�10�2 Dual shaft high bypass turbofan ....................................101 4�10�3 Determination of net thrust ............................................104 4�10�4 Net thrust in takeoff .......................................................105

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4�10�5 Net thrust in cruise .........................................................106 4�10�6 Specific fuel consumption in cruise ...............................106 4�11 Turboprops ..................................................................................107 4�11�1 Takeoff distance .............................................................109 4�11�2 Turboprop cruise requirements ......................................109 4�11�3 Estimating takeoff thrust and specific fuel

consumption ...................................................................112 4�12 Engine-out operation and balanced field length .........................113 4�13 Design summary .........................................................................115 4�14 Nomenclature ..............................................................................116 4�14�1 Subscripts .......................................................................117

References ...................................................................................118

CHAPTER 5 Wing Design ������������������������������������������������������� 119 5�1 General wing planform characteristics .......................................120 5�1�1 The straight-tapered wing planform ................................122 5�1�2 Cranked wing planform ...................................................123 5�1�3 Wing dihedral ..................................................................126 5�2 General airfoil characteristics .....................................................126 5�2�1 Airfoil sections ................................................................128 5�2�2 Airfoils at angle of attack ................................................130 5�2�3 Airfoil selection ...............................................................133 5�2�4 Compressibility effects on airfoils ...................................137 5�2�5 Computational resources for airfoil analysis

and design ........................................................................142 5�3 Lifting characteristics of the wing ..............................................143 5�3�1 Determination of the wing lift curve slope ......................143 5�3�2 Sample calculation of the wing lift curve slope ..............144 5�4 Determination of wing maximum lift in the cruise

configuration ...............................................................................145 5�4�1 Subsonic maximum lift of high-aspect-ratio wings .........146 5�4�2 DATCOM method for untwisted, constant-section

wings ................................................................................147 5�4�3 Sample calculation for an untwisted, constant-section

wing .................................................................................150 5�4�4 Maximum lift of unswept twisted wings with

varying airfoil sections ....................................................151 5�4�5 Reynolds number in flight ...............................................152 5�4�6 Maximum lift of swept and twisted wings with

varying airfoil sections ....................................................154 5�4�7 A simple modified lifting line theory for CL,max .............158

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5�4�8 Comparison of span loading and the modified lifting line methods ..........................................................160

5�4�9 The pressure difference rule for CL,max ...........................162 5�5 High lift devices ..........................................................................164 5�5�1 Airfoil with trailing edge flaps ........................................167 5�5�2 DATCOM method for trailing edge flaps ........................170 5�5�3 Sample calculation of airfoil with a trailing

edge flap ...........................................................................172 5�5�4 Airfoil with leading edge slats or flaps ............................173 5�5�5 DATCOM method for leading edge slats

and flaps ...........................................................................174 5�5�6 Sample calculations of airfoil with a leading

edge slat ...........................................................................177 5�5�7 Combining leading and trailing edge devices

on airfoils .........................................................................179 5�6 Determination of CL,max for the wing in takeoff and

landing configurations ................................................................181 5�6�1 Application of high lift devices on wings ........................181 5�6�2 Determination of ΔCL,max for the wing due to flaps .......186 5�6�3 Determination of ΔCL,max for the wing due to slats ........187 5�6�4 Sample calculation for flaps and slats .............................189 5�7 Development and layout of the preliminary wing design ...........191 5�7�1 Aspect ratio ......................................................................191 5�7�2 Taper ratio and the root chord ..........................................193 5�7�3 Wing relative thickness and airfoil selection ...................195 5�7�4 Wing-mounted engines and a cranked trailing edge ........197 5�7�5 Placement of high lift devices .........................................198 5�7�6 Wingtip treatments...........................................................199 5�7�7 Winglets ...........................................................................201 5�7�8 Raked wingtips ................................................................203 5�7�9 Wing dihedral and incidence ...........................................204 5�8 Design summary .........................................................................205 5�9 Nomenclature ..............................................................................208 5�9�1 Subscripts ........................................................................209

References ...................................................................................210

CHAPTER 6 Tail Design ��������������������������������������������������������� 213 6�1 Preliminary tail design ................................................................213 6�1�1 Tail surface characteristics ...............................................215 6�1�2 Preliminary tail sizing ......................................................217 6�2 Refined horizontal tail design .....................................................221

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6�2�1 Equilibrium conditions ....................................................221 6�2�2 Trim and longitudinal static stability ...............................224 6�2�3 The stick-fixed neutral point ............................................225 6�2�4 The stick-fixed static margin ...........................................229 6�2�5 Estimate of horizontal tail area based on a stability

requirement ......................................................................230 6�3 Refined vertical tail design .........................................................235 6�3�1 Equilibrium conditions ....................................................235 6�3�2 Trim and lateral static stability ........................................238 6�3�3 Horizontal and vertical tail placement .............................241 6�3�4 Example calculation of vertical tail stability

derivative..........................................................................245 6�4 Design summary .........................................................................248 6�5 Nomenclature ..............................................................................248 6�5�1 Subscripts ........................................................................250

References ...................................................................................250

CHAPTER 7 Landing Gear Design ������������������������������������������� 251 7�1 Introduction .................................................................................251 7�2 General characteristics of commercial jet transport

landing gear ................................................................................252 7�2�1 Quasi-static loads on landing gear ...................................252 7�2�2 Dynamic loads in landing ................................................254 7�2�3 Location of the main gear ................................................257 7�2�4 Location of the nose gear ................................................259 7�2�5 Ground clearance in takeoff and landing .........................261 7�2�6 Operational considerations for positioning the

landing gear .....................................................................264 7�2�7 Maneuverability in ground operations .............................266 7�2�8 Powered wheel-drive systems ..........................................267 7�3 Aircraft tires and wheels .............................................................268 7�3�1 Load requirements ...........................................................271 7�3�2 Landing gear configurations ............................................275 7�4 Shock absorbing landing gear struts ...........................................277 7�4�1 Sizing the landing gear struts ..........................................280 7�4�2 Dynamic landing gear analysis ........................................283 7�4�3 Landing gear strut design example ..................................285 7�5 Landing gear brake systems ........................................................287 7�5�1 Tire, wheel, and brake selection example ........................293 7�6 Landing gear retraction ...............................................................295 7�7 Design summary .........................................................................298

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7�8 Nomenclature ..............................................................................298 7�8�1 Subscripts ........................................................................300 References ...................................................................................300

CHAPTER 8 Refined Weight and Balance Estimate ������������������ 301 8�1 Process for refining the weight

estimate .......................................................................................302 8�2 Limit load factor .........................................................................302 8�3 The design dive speed .................................................................303 8�4 Wing group weight .....................................................................305 8�5 Fuselage group weight ................................................................308 8�6 Landing gear group weight .........................................................310 8�7 Tail group weight ........................................................................312 8�8 Propulsion group weight .............................................................314 8�9 Nacelle group weight ..................................................................315 8�10 Flight controls group weight .......................................................318 8�11 Auxiliary power unit group weight .............................................320 8�11�1 Torenbeek’s correlation ..................................................322 8�11�2 Modified correlation .......................................................322 8�11�3 Kroo’s correlation ..........................................................322 8�11�4 Relating APU group weight to aircraft

gross weight ...................................................................322 8�12 Instrument group weight .............................................................324 8�13 Hydraulic and pneumatic group weight ......................................325 8�14 Electrical group weight ...............................................................326 8�14�1 The all-electric airplane .................................................327 8�14�2 “Greener” APUs .............................................................328 8�15 Avionics group weight ................................................................328 8�16 Equipment and furnishing group weight ....................................329 8�17 Air conditioning and anti-icing

group weight ...............................................................................331 8�18 Wing group center of gravity ......................................................332 8�19 Fuselage group center of gravity ................................................334 8�20 Landing gear group center of gravity .........................................337 8�21 Tail group center of gravity.........................................................337 8�22 Propulsion group center of gravity .............................................338 8�23 Aircraft center of gravity ............................................................339 8�24 Design summary .........................................................................344 8�25 Nomenclature ..............................................................................345 8�25�1 Subscripts ........................................................................346

References ...................................................................................347

xiContents

CHAPTER 9 Drag Estimation �������������������������������������������������� 349 9�1 Introduction .................................................................................350 9�2 Skin friction drag ........................................................................351 9�2�1 Laminar flow ....................................................................351 9�2�2 Turbulent flow ..................................................................352 9�2�3 Compressibility effects on skin friction ...........................354 9�2�4 Surface roughness effects on skin friction .......................355 9�2�5 The equivalent flat plate for calculating component

drag ..................................................................................357 9�3 Form drag ....................................................................................359 9�4 Drag build-up by components.....................................................360 9�5 Wing and tail drag .......................................................................362 9�5�1 Effect of boundary layer transition on wing and

tail drag ............................................................................366 9�5�2 Wing and tail wetted areas ...............................................368 9�6 Fuselage drag ..............................................................................368 9�7 Nacelle and pylon drag ...............................................................370 9�8 Landing gear drag .......................................................................372 9�9 Flap and slat drag ........................................................................372 9�10 Other drag sources ......................................................................373 9�11 Calculation of the zero-lift drag coefficient neglecting

wave drag ....................................................................................373 9�12 Compressibility drag at high subsonic and low

transonic speeds ..........................................................................376 9�13 The area rule ...............................................................................378 9�14 Calculation of the wave drag coefficient ....................................379 9�14�1 Perkins and Hage method ..............................................379 9�14�2 Shevell Method ..............................................................383 9�14�3 DATCOM method ..........................................................384 9�14�4 Korn equation method ....................................................386 9�14�5 Evaluation of the methods..............................................386 9�15 Effects of sweepback ..................................................................388 9�15�1 Practical sweepback corrections for the

estimation methods ........................................................391 9�15�2 Other three-dimensional wing effects ............................392 9�16 The drag coefficient of the airplane ............................................393 9�17 Thrust available and thrust required ...........................................396 9�18 Design summary .........................................................................400 9�19 Nomenclature ..............................................................................400 9�19�1 Subscripts ........................................................................402

References ...................................................................................403

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CHAPTER 10 Aircraft Performance ...........................................................405 10�1 The range equation .....................................................................406 10�1�1 Factors influencing range ...............................................408 10�2 Takeoff performance ...................................................................409 10�2�1 Ground run .....................................................................410 10�2�2 Air run ............................................................................417 10�2�3 Approximate solution for takeoff ...................................419 10�2�4 Speeds during the takeoff run ........................................420 10�2�5 Continued takeoff with single engine failure .................422 10�2�6 Aborted takeoff with single engine failure.....................425 10�2�7 The balanced field length ...............................................427 10�3 Climb ..........................................................................................429 10�3�1 Climb profile ..................................................................430 10�3�2 Time to climb .................................................................431 10�3�3 Distance to climb ...........................................................432 10�3�4 Fuel to climb ..................................................................433 10�4 Descent .......................................................................................433 10�4�1 Descent profile and performance ...................................434 10�4�2 Time to descend .............................................................434 10�4�3 Distance to descend ........................................................435 10�4�4 Fuel to descend ..............................................................435 10�5 Landing .......................................................................................435 10�5�1 Air run ............................................................................435 10�5�2 Ground run .....................................................................437 10�6 Turboprop-powered aircraft ........................................................440 10�6�1 Turboprop range .............................................................440 10�6�2 Turboprop takeoff ground run ........................................441 10�6�3 Turboprop takeoff air run ...............................................441 10�6�4 Approximate solution for turboprop takeoff ..................442 10�6�5 Turboprop propeller characteristics ...............................442 10�6�6 Selecting a propeller ......................................................444 10�7 The air data system .....................................................................446 10�8 Design summary .........................................................................449 10�9 Nomenclature ..............................................................................449 10�9�1 Subscripts ........................................................................451 References ...................................................................................452

CHAPTER 11 Aircraft Pricing and Economic Analysis ��������������� 453 11�1 Introduction .................................................................................453 11�2 Capital cost .................................................................................454

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11�3 Direct operating cost ...................................................................459 11�3�1 Block speed ....................................................................460 11�3�2 Block fuel .......................................................................461 11�3�3 Flight crew costs ............................................................461 11�3�4 Fuel and oil costs ...........................................................462 11�3�5 Hull insurance ................................................................464 11�3�6 Airframe maintenance labor and materials ....................464 11�3�7 Engine maintenance labor and materials .......................466 11�3�8 Maintenance burden .......................................................467 11�3�9 Depreciation ...................................................................467 11�3�10 Direct operating cost ......................................................468 11�4 Indirect operating cost ................................................................468 11�5 Breakeven load factor .................................................................471 11�6 Design project activity ................................................................473 11�7 Nomenclature ..............................................................................473 11�7�1 Subscripts ........................................................................474

References ...................................................................................474

APPENDIX A Airfoil Characteristics ����������������������������������������� 477

APPENDIX B 1976 US Standard Atmosphere Model ������������������ 487

APPENDIX C Airfoil and Wing Theory and Analysis ������������������� 497

APPENDIX D Graphs of Critical Mach Number �������������������������� 561

APPENDIX E Units and Conversion Factors ������������������������������� 565

APPENDIX F General Database for Commercial Aircraft ������������� 571

Index �������������������������������������������������������������������������������������� 585