Synthesis of an Aircraft Featuring a Ducted-Fan Propulsive Empennage

126 Pages·2017·9.18 MB·English

Synthesis of an Aircraft Featuring a
Ducted-Fan Propulsive Empennage
N.H.M. van den Dungen
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S A F
YNTHESIS OF AN IRCRAFT EATURING A
D -F P E
UCTED AN ROPULSIVE MPENNAGE
by
N.H.M.vandenDungen
inpartialfulfillmentoftherequirementsforthedegreeof
MasterofScience
inAerospaceEngineering
attheDelftUniversityofTechnology,
tobedefendedpubliclyonTuesdayApril18,2017at13:00h.
Studentnumber: 4133420
Thesisregistrationnr: 156#17#MT#FPP
Thesiscommittee: Prof.dr.ir.L.L.M.Veldhuis TUDelft Headofdepartment
dr.ir.R.Vos TUDelft Supervisor
dr.ir.S.Hartjes TUDelft Externalcommitteemember
ir.N.vanArnhem TUDelft Supervisor
Anelectronicversionofthisthesisisavailableathttp://repository.tudelft.nl/.

P
REFACE
ThewordswritteninthisthesisbelongtothelastonesIeverputonpaperasaMasterstudentofthefacultyof
AerospaceEngineeringattheDelftUniversityofTechnology.Withthecompletionofthisthesis,andtherefore
theMastertrackofFlightPerformance&Propulsion,theyearsofstrugglingasastudentwillbeoverandthe
decadesofworkingasanengineerwillstart.
IstillrememberthedayIsignedupforthethesisontheDelftUniversityUnconventionalConfiguration,
orsimplycalledtheDUUC.BackinNovember2015IwasfinishingmylastmonthofinternshipatTUIfly
Engineering,whenIdiscoveredtheDUUCconceptontheBlackBoardpagewhilesearchingforpossiblethe-
sistopics. BycoincidenceImetmytobecomethesissupervisorRoelofVosonaThursdaymorningonDelft
CentralStation,whenIwasabouttotakethetraintoSchiphol.Afterhavingaquickword,wewerebothcon-
vincedthatmynextchallengewouldconsistofaoneyearresearchtoanaircraftwithaducted-fanpropulsive
empennage. Myfirstimpressionoftheconceptwas: "whereisthetail,andwhyaretheengineslocatedaft
ofthefuselage?"Thisfirstimpressionwasaguidelinethroughoutthethesisresearchandallowedmetobe
comprehensiveandcriticaltowardsthefindingsIdiscoveredinthepastyear.
AttheendIbelievethatthebiggestchallengeofmylastMasteryears, wasnotthefactthatIonlyhad
achallengingthesistopic, butthecombinationofworkingontwocomplexprojectswithinthesametime
frame. ShortlytwomonthsearlierbeforeIdevotedmythesistotheDUUC,myextracurricularactivitiesat
DelftAerospaceRocketEngineering(DARE)tookanewturnwiththestartofprojectAether, asupersonic
technologydemonstratorforfutureDAREspaceflightsfeaturingactiveaerodynamicstabilizationandhigh-
speedparachutedeployment.Attheendofthesummerof2015about30motivatedDAREstudentsdecided
tocombinetheirvisionsintothedevelopmentofonelargeresearchrocket,anditbecamemydutyasproject
managertoguideAetheranditsstudentstowardsasuccessfulflight.
ThecombinedresearchofthesetwoprojectsmadethelastyearoftheAerospaceMasterthemostdifficult
challengeIhadtofacesofar.DuringthedaytimeIwastryingtosolvetheintegrationandstabilityproblems
oftheDUUC,andduringthenighttimemyteamandIweresolvingtheintegrationproblemsofamodular
supersonicrocketdesign. Nevertheless,withtherightclearengineeringfocus,dedicationandmotivation,
andsupportfromfriends,family,andcolleagues,Imanagedtocompletethewhatseemedtobeimpossible.
ByquotingWalterD.Wintle:"Butsoonerorlaterthemanwhowinsistheonewhothinkshecan."
TheconceptualdesignoftheDUUCwasatoughstudy, inthesensethatalargerangeofaeronautical
disciplineshadtobeinvestigated,whereabalancebetweendetailedanalysisandoverallintegrationhadto
bemaintained. AndsometimesIfoundanswerstoresearchquestionswhichwerenottheonesIhopedto
find. However,intheendIreallyenjoyedworkingonconceptualaircraftdesign,becausethatisthemain
reasonwhyIdecidedtostudyAerospaceEngineeringinthefirstplace.
FirstofallIwouldliketothankmysupervisorRoelofVos,whoallowedmetoworkonthechallengingtopic
ofconceptualaircraftdesign,andwhosupportedmethroughouttheentirethesis.Hiswillingnesstoprovide
feedbackonmyworkatanytimehasmygreatestgratitude. SecondlyIwouldliketothankthemembersof
mygraduationcommittee,LeoVeldhuisandSanderHartjes,forthetimetheyspentinassessingmywork. I
wouldliketothankNandovanArnhemforhisinvaluablefeedbackontheDUUCconcept,andthetimehe
waswillingtospentwithmetosolveindepthproblemsoftheaircraftdesign. FurthermoreIwouldliketo
thankVikeshHarinarain,forourcooperationintheresearchtoducted-fanimplementationinaircraft.
Iwouldliketothankallmyfriends,forthesupporttheygavemeduringthethesis,andforthefunwehad
besidesallourhardstudywork.Andlastbutnotleast,Iwouldliketoexpressmygreatgratitudetowardsmy
family,andespeciallymyparentsforthesupporttheygavemethroughoutmyentirestudiesinDelft.
N.H.M.vandenDungen
Delft,April,2017
iii

A
BSTRACT
Researchintomoreefficientandsustainableaircraftisadrivingmotivationforaircraftengineerstodevelop
innovativeconcepts.Theadvancedconventionalairlinersofthepresentdaystilllooksimilartothosedevel-
opedintheearlyyearsofaviation. Insearchofrevolutionarysustainableconcepts,radicalout-of-thebox
designsarebeingexplored.
A thesis research is done to investigate the feasibility of the conceptual design of the Delft University
UnconventionalConfiguration(DUUC),anaircraftfeaturingaducted-fanpropulsiveempennage(DFPE).By
integratingthepropulsionsystemwithastabilizingring-wingliftingsurfaceandjetcontrolvanes,alighter
andmorefuelefficientdesigncouldbeachieved. Themainbenefitoftheductedfanisanincreasedstatic
thrustperformance,whereadditionallytheefficientring-wingdesigncontributestothestabilityandbalance
oftheaircraft. Secondarybenefitsincludeblade-containmentprotectionandnoiseshielding. Thisthesis
researchfocusesonducted-fansystem(DFS)performanceestimation,propulsionsystemmassestimation,
aircraftsizingforlongitudinalstaticstabilityandbalance,andaircraftperformancecomparison.
The Aircraft Design Initiator, a program designed to quickly synthesize realistic aircraft for initial per-
formancestudiesofnewconcepts, isusedtomakemodelsoftheDUUCandasimilarsizedconventional
referenceaircraft. OncebothaircraftaremodeledwithintheInitiator,theirperformancesarecomparedin
termsofoperationalemptymass(OEM),maximumtake-offmass(MTOM),fuelconsumption,andaircraft
drag,tostudytheeffectoftheDUUCconceptontheoverallaircraftdesign. Basedontheoperationalveloc-
ityregionofductedfansandthepreviousresearchwithintheInitiatortoturbopropaircraft,theATR72-600
(high-wing,T-tail,turboprop)ischosenasreferenceaircraft. AsignificantupdatetotheInitiatorcorewas
donesuchthattheuserhasthefreedomtodesigneachofthefollowingpropulsioncomponentsindividually:
motor(gas-generator),centerbody,fan,nacelle(duct)andpylon.
Thefandiameterissizedbasedonthefanrotationalvelocity,cruiseMachnumber,andmaximumfantip
Machnumber. Dividingthefandiameterbytheductaspectratioyieldstheductchordlength. Combined
withapredefinedductairfoil,fan-ductlongitudinaloffset,andfan-ducttipclearance,thetotalDFSgeometry
isdetermined. Thepylonissizedsuchthatitleavesaclearancebetweentheductandthefuselage. Forthe
stabilityandbalancecalculations,theequivalenttailarearesultsfromthehorizontalprojectedsurfaceareaof
theductandpylon.Thepylonareainsidetheductdoesnotcontributetothetailarea,onlytheareabetween
theductandthefuselageandthepylonareaaftoftheduct.
AerodynamicpropertiesoftheDFPEarederivedfromacombinationofexistingempiricalmethodsfor
planarwings(forthepylon)andring-wings(fortheduct). Basedonwindtunnelexperimentsthrusteffects
ontheliftpropertiesoftheDFSareimplemented,whichincreaseboththeliftgradientasthemaximumlift
coefficient. Becauseofunknowninteractionsbetweentheduct,fan,centerbody,pylon,andjetvanes,itis
assumedthatthemaximumliftcoefficientoftheentireDFPEisdominatedbytheDFSonly.Thegeometries
ofthejetvanesarenotsized,howevertheirthrust-vectoringeffectsareincludedinthecalculationofthelift
coefficient, whereitisassumedbasedonexperimentalwindtunnelresearchthattheywillincreasethelift
with20%foramaximumvanedeflection.
Apropelleranalysisprogramisdeveloped,whichintegratesunductedandducted-fananalysistoolsto
performpropellerperformancecomparisonsandaparametricducted-fandesignstudy. Analysiswiththe
Ducted Fan Design Code (DFDC) tool indicates that a large duct aspect ratio is beneficial in terms of the
propulsiveefficiency.DFDCisimplementedintheInitiator,howeveritisnotactiveincalculatingthepropul-
siveefficiencies.TheDFDCmodulerequiresadetaileddesignofthefanbladegeometriesandductairfoil,to
resultinrealisticoutput,e.g. thrust,torque,power. Becausethefanbladegeometrydesignmoduleisbeing
developedinparallelbyanotherInitiatorthesis,theDUUCfangeometryischosenarbitrarilybasedonexper-
imentalresearchonductedfansystems.ThepropulsiveefficienciesoftheDUUCarebasedontheHamilton
StandardF568propellerinstalledontheATR72-600,whereitisassumedthattheDFShas10%highertake-off
propulsiveefficiencyduetotheincreasedstaticthrustperformance.
TheInitiatorClass2WeightEstimationmethodisupdatedwiththemodifiedenginemodel. Anaddi-
tionalcomponentbasedweightestimationmethodfortheductisimplemented. Firstofall,thealuminium
ductshellthicknessisbasedonthepressurevesseltheory,whichusesthestaticpressureandinternalduct
pressure.Theinternalductpressureduringmaximumthrustattake-offisacquiredwiththeDFDCmodule.
v
vi ABSTRACT
Theductshellmassscaleswithairfoilshape. Secondly,thethicknessofaKevlarbladecontainmentlineris
calculatedincaseofabladerelease.Themassofthebladecontainmentlinerisaboutoneorderofmagnitude
lower than the duct shell mass. A weight correction factor of 1.5 is included to account for the structural
reinforcementsinsidetheductandthejetvanes.Thepylonmassisassumedtobe30%ofitstipmass,which
consistsoftheengine,centerbody,fan,andduct. Becausetheductmassscaleswiththechordlengthand
ductdiameter,thepylonmassscalesaccordingly.
Sizingforlongitudinalstaticstabilityandcontrollability(LSSC),wherecontrollabilityreferstotrimming,
isidentifiedasthecruxoftheDUUCconcept. ForminimumOEMtheDFPEshouldbeassmallaspossible,
however for LSSC it is beneficial to have a certain tail area, to prevent that the DFPE generates too large
downforcestomaintainabalancedaircraft.Torenbeek’s"X-Plot"methodismodified,suchthathisequations
canbeusedtodeterminetheLSSClimitsfortheDUUC.BecausethetailareaoftheDFPEisfixedbychoosing
theductaspectratioandfandiameteratthebeginningoftheaircraftdesignconvergence,theDUUCcanonly
modifythewingpositiontoguaranteeastableandtrimmabledesign. Awing-positioningdiagramaidsthe
aircraftdesignertoplacethewingasmuchforwardaspossible,whilecomplyingtotheLSSCrequirements.
ThetrimdragoftheDUUCiscalculatedbasedontheresultsofthetrimdiagram,whereitisassumed
thatalinearrelationbetweenthetail-offliftandthetaildownforceexists. Itisassumedthatthecenterof
gravity(c.g.) shiftduringflightiswithin1%ofthemeanaerodynamicchord(MAC),suchthatthetailarm
doesnotchange. Bydoingso,theforwardc.g. locationacquiredfromtheaircraftloadingdiagramcanbe
usedtodeterminethemomentarmoftheDFPE.Asuperpositionmethodisappliedtocombinethetail-off
liftdragpolarwiththetaildownforceandtrimdrag,toacquirethetotaltrimmedaircraftlift-dragpolar.
Topreventbookkeepingerrorsthefollowingruleismaintained: AllDFPEpropertieswhichcontributein
generatingadownforcearebookedunderthehorizontalstabilizercontributions, andallparameterswhich
contributeingeneratingdragduetothefanfrontalareaarebookedunderthepropulsioncontributions.
TheATR72-600baselinemodelhas-2.2%MTOM,-0.8%OEM,and-22.1%harmonicfuelmass,compared
tothereferenceaircraft.Thelargediscrepancyinthefuelmassiscausedbyanunderestimationofthepower
loading,whichislimitedbytherequirementtohaveaclimbgradientof2.1%afterabalkedlandingwithone
engineout. Withahigherrequiredenginepower,theenginemassincreases. Thiseffectispresentforboth
theATR72-600andDUUCmodels,howevertheDUUCexperiencesalargeraftshiftedOEMc.g.
IncludingtheuncertaintiesintheDFPEweightestimation, theDUUCindicatesthattheMTOMvaries
from +5.8% to +20.2%, OEM varies from +9.1% to +31.8%, and harmonic fuel burn varies from +8.4% to
+21.9%,withrespecttotheATR72-600Initiatormodel.DuetotheheavyDFPE,theOEMincreases.Therefore
theenginesneedtobemorepowerfultolift-offtheaircraft,whichincreasestheaircraftmassinthenextit-
erationinthedesignconvergence.Secondly,theheavyDFPEshiftsthec.g.faraft.Thisreducesthemoment
armbetweentheaerodynamiccenter(a.c.)oftheDFPEandc.g.,andthereforetheDFPEneedstogeneratea
largerdownforcetokeeptheaircraftbalancedduringflight.Thelargedownforceresultsinalargetrimdrag,
whichconsequentlyincreasesthetotalfuelconsumption. Thea.c. ofthetaillessaircraftislocatedafterthe
mostforwardc.g.location,duetothecontributionsofthefuselageshapeandthefrontalareaofthefans.
Asensitivityanalysisindicatesthatsmallerducts,bydecreasingitschordordiameter,resultinalighter
andmorefuelefficientdesign.Unfortunatelythedecrementinductsizeislimitedbythestabilityandbalance
constraints,andmanualchecksarerequiredtoverifythefeasibilityofthewing-positioningdesignspace. If
theductsbecome too small, thehorizontal projectedsurfaceareaisnotbigenoughtogenerateacertain
downforce,assuchtheaircraftbecomesinstable.
Asensitivityanalysisofthetake-offpropulsiveefficiencyconcludesthatanincreaseinstaticthrustper-
formancehasmarginaleffectontheoverallaircraftmassesandfuelconsumption.Thetake-offfuelsavingis
insignificantcomparedtothecruisephasefuelburn.Thereforethemainperformancebenefitoftheducted
fan, theincreasedstaticthrustperformancecomparedtosimilarsizedunductedpropellers, isnotsignifi-
cantlybeneficialfortheoverallDUUCconcept.
An"ideal"aircraftcomparisonwithmaximumpropulsiveefficienciesand"super-lightweight"ductde-
signforboththeATR72-600andDUUCmodelsisperformed. TheidealDUUCshows+5.1%MTOM,+7.8%
OEM,+7.6%fuelconsumption.ThisresultindicatesthatthestatedassumptionsonDFPEpropulsiveperfor-
manceandweightestimationdonotchangetheoveralloutcomeoftheaircraftcomparison.
ThefeasibilitystudytotheDUUCconceptshowsthattheheavyDFPEandlargetrimdragmakeitun-
likelythatamorefuelefficientandlighterdesignresultscomparedtoasimilarsizedconventionalreference
aircraft.
C
ONTENTS
Preface iii
Abstract v
Nomenclature xi
ListofFigures xv
ListofTables xvii
1 Introduction 1
1.1 HistoryofDucted-FanAircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 DefinitionofaDucted-FanEngine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 AircraftDesignInitiator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 ResearchObjective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.5 ScopeofThesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.6 OutlineofThesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 TheoryofDuctedandUnductedFans 9
2.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 SizingoftheDucted-FanPropulsiveEmpennage . . . . . . . . . . . . . . . . . . . . . 9
2.1.2 AdvanceRatio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.3 ActivityFactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.4 PropellerPerformanceCoefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 PropellerPerformanceAnalysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.1 ActuatorDiskTheory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.2 BladeElementMethod. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 Ring-Wing&DuctedFanAerodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.1 Ring-WingLiftGeneration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.2 Ring-WingAerodynamicMoment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3.3 DuctedFan:ThrustEffectsonRing-Wing . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3.4 DFPEParasiteDragEstimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3 PropellerAnalysisProgram 19
3.1 Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.1 BEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.2 XROTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.3 DFDC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2.1 AirfoilPolarInterpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.2 MultiAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.3 PropellerMapAnalysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3.1 BEMvsXROTOR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3.2 DFDCValidation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3.3 MultiAnalysisforDuctedFans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4 PropulsionWeightEstimation 27
4.1 Turboprop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.1.1 Raymer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.1.2 Roskam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.1.3 TurbopropWeightEstimationTrade-Off. . . . . . . . . . . . . . . . . . . . . . . . . . 28
vii
viii CONTENTS
4.2 Propeller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.1 Torenbeek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.2 HamiltonStandard-NASA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.3 PropellerWeightEstimationTrade-Off. . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.3 Duct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.1 Raymer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.2 Torenbeek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3.3 CranfieldUniversitySemi-EmpiricalMethod . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.4 CranfieldUniversityComponent-BasedMethod. . . . . . . . . . . . . . . . . . . . . . 31
4.4 Pylon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5 SizingforLongitudinalStaticStabilityandControllability 35
5.1 TailVolumeCoefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.2 HorizontalTailEffectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.3 X-PlotMethod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.4 LongitudinalStaticStability&ControllabilityConstraints . . . . . . . . . . . . . . . . . . . . 37
5.4.1 FreeBodyDiagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.4.2 SizingforStickFixedLongitudinalStaticStability . . . . . . . . . . . . . . . . . . . . . 38
5.4.3 SizingforLongitudinalStaticControllability(Trimming) . . . . . . . . . . . . . . . . . 38
5.4.4 BookkeepingofDFPEProperties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.5 DUUCWing-Positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.5.1 GeneralProcedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.5.2 Wing-PositioningPlot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.6 Trimming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.6.1 TrimDiagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.6.2 TrimDrag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
6 Results&Discussion 47
6.1 ReferenceAircraftValidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
6.1.1 PropellerPerformance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
6.1.2 GeneralCommentsonFinalResult . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
6.1.3 Class2WeightEstimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
6.2 DUUCBaseline&ComparisonATR72-600 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
6.2.1 PropellerPerformance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
6.2.2 GeneralCommentsonFinalResult . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
6.2.3 Class2WeightEstimationComparison . . . . . . . . . . . . . . . . . . . . . . . . . . 53
6.2.4 DragComparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
6.2.5 HorizontalStabilityEstimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
6.3 SensitivityAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
6.3.1 DuctAspectRatio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
6.3.2 FanTipMachNumber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
6.3.3 FanRPM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
6.3.4 NumberofFanBlades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.3.5 Take-OffPropulsiveEfficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
6.3.6 Take-OffDistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.3.7 PropulsionWeightFactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.3.8 EngineLongitudinalLocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.3.9 IdealAircraft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.3.10 SummaryonDesignPhenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
7 Conclusion&Recommendations 73
7.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.1.1 ImplementationofTurbopropReferenceAircraftintheInitiator. . . . . . . . . . . . . . 73
7.1.2 ImplementationofDUUCConceptintheInitiator . . . . . . . . . . . . . . . . . . . . 74
7.1.3 PerformanceComparisonofDUUCandATR72-600Models. . . . . . . . . . . . . . . . 74
7.1.4 DUUCSensitivityAnalysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
7.1.5 OverallConclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75