Flight Physics: Essentials of Aeronautical Disciplines and Technology, with Historical Notes

540 Pages·2009·17.29 MB·English

by  E. Torenbeek

Flight Physics
E. Torenbeek • H. Wittenberg†
Flight Physics
Essentials of Aeronautical Disciplines and Technology,
with Historical Notes
E.Torenbeek H.Wittenberg†
DelftUniversityofTechnology
Delft,TheNetherlands
FromtheoriginalDutch“Aëronautiek:GrondslagenenTechniekvanhetVliegen”,DelftUniver-
sityPress,2002.Translatedandre-editedbySimeonCalvertandEgbertTorenbeek.
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ISBN 978-1-4020-8663-2 e-ISBN 978-1-4020-8664-9
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Contents
Preface...................................................... ix
1 HistoryofAviation ....................................... 1
1.1 Introduction. ......................................... 1
1.2 Earlyhistoryandtheinvention ofballooning .............. 3
1.3 Theperiodbetween1799and1870 ...................... 8
1.4 Thedecadesbetween1870and1890 ..................... 12
1.5 From1890untiltheWrightFlyerIII ..................... 15
1.6 Europeanaviation between1906and1918 ................ 22
1.7 Aviationbetweentheworldwars ........................ 29
1.8 Developmentafter1940................................ 37
Bibliography ............................................. 45
2 IntroductiontoAtmosphericFlight......................... 47
2.1 Flying–Howisthatpossible?........................... 47
2.2 Staticanddynamicaviation............................. 49
2.3 Forcesontheaeroplane ................................ 55
2.4 Lift,dragandthrust ................................... 58
2.5 Propertiesofair....................................... 62
2.6 Theearth’satmosphere................................. 67
2.7 Thestandard atmosphere ............................... 69
2.8 Atmosphericflight .................................... 78
Bibliography ............................................. 84
3 Low-SpeedAerodynamics ................................. 87
3.1 Speeddomainsandcompressibility ...................... 88
3.2 Basicconcepts........................................ 89
3.3 Equationsforsteadyflow............................... 93
3.4 Viscousflows.........................................102
v
vi Contents
3.5 Theboundary layer....................................105
3.6 Flowseparation anddrag ...............................109
3.7 Shapeandscaleeffectsondrag..........................116
Bibliography .............................................123
4 LiftandDragatLowSpeeds...............................125
4.1 Functionandshapeofaeroplane wings ...................125
4.2 Aerofoilsections......................................128
4.3 Circulation andlift ....................................137
4.4 Aerofoilsectionproperties..............................145
4.5 Winggeometry .......................................153
4.6 High-aspect ratiostraight wings .........................158
4.7 Low-aspectratiowings ................................169
4.8 Thewholeaircraft.....................................172
Bibliography .............................................178
5 AircraftEnginesandPropulsion ...........................181
5.1 Historyofenginedevelopment ..........................181
5.2 Fundamentals ofreaction propulsion .....................196
5.3 Engineefficiencyandfuelconsumption...................205
5.4 Pistonenginesinaviation ..............................209
5.5 Gasturbineenginecomponents..........................215
5.6 Non-reheated turbojet andturbofan engines ...............221
5.7 Turbopropandturboshaft engines........................227
5.8 Gasturbineengineoperation............................231
5.9 Propellerperformance .................................236
Bibliography .............................................251
6 AeroplanePerformance ...................................253
6.1 Introduction. .........................................253
6.2 Airspeedandaltitude ..................................258
6.3 Equationsofmotionforsymmetricflight..................260
6.4 Steadystraight andlevelflight ..........................265
6.5 Climbanddescent.....................................279
6.6 Glidingflight.........................................288
6.7 Cruisingflight ........................................292
6.8 Take-offandlanding...................................302
6.9 Horizontalsteadyturn .................................314
6.10 Manoeuvre andgustloads ..............................319
Bibliography .............................................324
FlightPhysics vii
7 StabilityandControl .....................................327
7.1 Flyingqualities .......................................328
7.2 Elementaryconcepts anddefinitions......................333
7.3 Tailsurfacesandflightcontrol ..........................342
7.4 Pitchingmomentofaerofoils............................349
7.5 Staticlongitudinal stability .............................358
7.6 Dynamiclongitudinal stability ..........................368
7.7 Longitudinal control...................................371
7.8 Staticlateralstability ..................................384
7.9 Dynamiclateralstability ...............................388
7.10 Lateralcontrol........................................391
7.11 Stallingandspinning ..................................395
Bibliography .............................................401
8 HelicopterFlightMechanics ...............................405
8.1 Helicoptergeneral arrangements.........................406
8.2 Hoveringflight .......................................408
8.3 Therotorinlevelflight.................................413
8.4 Flightperformance ....................................417
8.5 Stabilityandcontrol ...................................422
Bibliography .............................................429
9 High-SpeedFlight ........................................431
9.1 Complications duetothecompressibility ofair ............431
9.2 Compressible flowrelationships .........................436
9.3 SpeedofsoundandMachnumber .......................441
9.4 Flowinachannel .....................................446
9.5 Shockwavesandexpansion flows........................450
9.6 High-subsonic speed...................................460
9.7 Transonicspeed.......................................468
9.8 Supersonic speed......................................476
9.9 Supersonic propulsion .................................488
9.10 Performanceandoperation .............................496
Bibliography .............................................509
A UnitsandDimensions .....................................511
B PrinciplesofAerostatics...................................517
Index .......................................................523
Preface
Knowledge is not merely everything we have come to know, but also ideas
we have pondered long enough to know in which way they are related, and
howtheseideascanbeputtopractical use.1
Modern aviation has been made possible as a result of much scientific re-
search. However, the very first useful results of this research became avail-
ableaconsiderable length oftimeaftertheaviation pioneers hadmadetheir
firstflights.Apparently, researchers werenotabletofindanadequateexpla-
nationfortheoccurrenceofliftuntilthebeginningofthe21stcentury.Also,
for the fundamentals of stability and control, there was no theory available
thatthepioneerscouldrelyon.Onlyafterthefirstmotorizedflightshadbeen
successfully made did researchers become more interested in the science of
aviation, whichfromthenonbegantotakeshape.
In modern day life, many millions of passengers are transported every
year by air. People in the western societies take to the skies, on average,
severaltimesayear.Especially inareas surrounding busy airports, travelby
plane has been on the rise since the end of the Second World War. Despite
becoming familiar with the sight of a jumbo jet commencing its flight once
or twice a day, many find it astonishing that such a colossus with a mass of
severalhundredthousandsofkilogramscanactuallyliftofffromtheground.
Itwillthenclimbtoover10kilometresaltitudewithinhalfanhour,maintain
a cruising speed of about 900 km/h for several hours, and evidently it costs
thecrewlittleornoefforttokeepthisaerialgiantundercontrol.Obviously,it
isimpossibletounravelthismysteryinjustafewwell-formulatedsentences
ormathematical expressions.
1FreecitationoftheGermanphilosopherGeorgChristophLichtenberg(1742–1799).
ix
x Preface
Thisbookfocuses onreaderswithadeeperinterest inaerospace technol-
ogy, who specifically seek insight into the movement of an aircraft through
the atmosphere. The book is an expansion of lecture material for freshmen
studying Aerospace Engineering at the Technical University of Delft in the
Netherlands, who have been taught by both authors in the period 1970 to
2000. The subjects selected are appropriate to an introductory course for
those participating in higher education in aerospace technology, also giving
the lecturer the means of compiling an examination. The material selected
is considered essential for students with the ambition to be active in air-
craft design anddevelopment. Thebook can also serveasan orientation for
thosewhoarestillconsidering studying aerospace engineering. Thelevelof
abstraction is appropriate to an introductory course in bachelor’s as well as
master’sstudies,thecontentsbeingintunewiththeknowledgeandabilityof
high-school graduates. Moreover,thisbookaddressesthoseinsomespecific
employment in the aviation world and who would like to orientate them-
selves in subjects not necessarily belonging to their area of expertise. The
authors also hope to spark the interest of readers not necessarily involved
with aviation professionally, but who seek to enrich their knowledge on the
fascinating subject of flight physics. After all, aviation is a very rewarding
fieldofstudythatisstillinfulldevelopment, captivating manypeople.
Forthetitleofthisbook,theterminologyFlightPhysicshasbeenchosen.
Thesewordsbestindicatetheprimarydisciplines andtechnologyconcerned
withaeronautics, thatis,applications toaircraftflightof
• aerodynamics,
• propulsion,
• performance,
• stabilityandcontrol.
The term flight mechanics is used for the combination of aircraft perfor-
mance, stability and control. The essential elements of aeronautics will be
discussedinlaterchapters.Thesewillbeprecededbyabird’seyeviewofthe
historicaldevelopmentofaviationandvariousbasicaspectsofflightphysics,
including properties of the atmosphere which have a great influence on the
airflowaroundamovingaircraft andonitspropulsion.
Thisbook is atranslation into English ofa book originally written in the
Dutch language. Some attention is, therefore, paid to remarkable contribu-
tionstoaeronautical researchanddevelopmentintheNetherlandsthatisnot
foundininternationaltextbooksandconsideredtobeofgeneralinterest.The
order inwhich the chapters in this book are set outis based on the practical
side of the topic being considered of greater interest for a first introduction
FlightPhysics xi
thanthetheoretical side.Theauthorshavetriedtolimitthedepthofthema-
terial as far as possible without falling into the trap of oversimplification.
Formulas andtheir derivation areexplained without presenting unnecessary
information, aiming for a broad insight into the physics of flight. To keep
the teaching material sufficiently elementary, the first chapters concentrate
onflightat(relatively)lowairspeed,atwhichthecompressibility ofairdoes
nothavesignificantinfluenceonaerodynamic characteristics. Thisismostly
the case with propeller aircraft and helicopters, but also jet-propelled air-
crafthavetooperatesatisfactorilyinthisairspeedregime.However,because
most jet aircraft can reach higher speeds – some can even exceed the ve-
locity of sound – the last chapter has been dedicated to complications that
can be expected in high-speed flight. The flight dynamics treated pertains
to aeroplanes – that is, fixed-wing aircraft – with the exception of achapter
dedicated tohelicopter flightmechanics.
Advancementsinflightphysicsoftentakeplaceatahighlevelofabstrac-
tion–inparticular aerodynamicsisknownasadifficultscientificdiscipline.
Moreover, the different disciplines are highly interrelated, and many topics
appear in several chapters. In the interest of good legibility, derivations and
theresultsthereofpresented inearlierorsubsequent chaptersarenotalways
referred toagain.Incopingwiththis,thereaderwillfindsomeassistance in
an extensive index of essential terminology typeset in italics. As a stimulus
for further reading, there is a fairly comprehensive bibliography at the end
of each chapter referring to (mainly) recently issued books. General books
dealing with aeronautics and aircraft design are listed at the end of the sec-
ondchapter,referencestoaerodynamicsarespreadoverthethird,fourthand
ninthchapter.
Subjectsdiscussedinthisbookareoftenindirectlyrelatedtoseveralother
disciplinesofaeronautics.Specifically,theseentailthestudyofaircraftstruc-
tures and materials, manufacture and production engineering, instruments
and avionics, control systems engineering, aircraft operation, and aircraft
conceptual design. Formanyofthesespecializations, knowledge ofthepre-
sentedmaterialwillbeuseful,andsometimesevenindispensable. Forexam-
ple, it is impossible to compute the loads acting on a wing structure under
design without any knowledge ofaerodynamics. Theinterdisciplinary char-
acter of aeronautical technology is certainly a complication in digesting the
presented material, but hopefully many readers will experience this as an
interesting challenge.
TheauthorsoftheoriginalbookinDutchhavetriedformanyyearstogive
theirstudentsaclearinsightinthemostessentialaspectsofflightphysicsand
aircraftdesign.Itisregrettablethatthesecondauthordidnotlivetoenjoythe