SustainableAviationTechnologyandOperations
ResearchandInnovationPerspectives
Editedby RobertoSabatini
Professor,DepartmentofAerospaceEngineering CollegeofEngineering
KhalifaUniversityofScienceandTechnology AbuDhabi,UAE
HonoraryProfessor,AerospaceEngineeringandAviation SchoolofEngineering,STEMCollege
RMITUniversity,Melbourne Victoria,Australia
AlessandroGardi
AssistantProfessor,DepartmentofAerospaceEngineering CollegeofEngineering
KhalifaUniversityofScienceandTechnology AbuDhabi,UAE
AssociateofRMITUniversity AerospaceEngineeringandAviation,SchoolofEngineering STEMCollege,Melbourne Victoria,Australia
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Names:Sabatini,Roberto,editor.|Gardi,Alessandro,editor.
Title:Sustainableaviationtechnologyandoperations:researchand innovationperspectives/RobertoSabatini,Professor,DepartmentofAerospace Engineering,KhalifaUniversityofScienceandTechnology,AbuDhabi, UAE;AlessandroGardi,AssistantProfessor,DepartmentofAerospace Engineering,KhalifaUniversityofScienceandTechnology,AbuDhabi,UAE
Description:Hoboken,NJ,USA:Wiley,2024.|Series:Aerospaceseries
Identifiers:LCCN2020025457(print)|LCCN2020025458(ebook)|ISBN 9781118932582(cloth)|ISBN9781118932612(adobepdf)|ISBN 9781118932605(epub)
Subjects:LCSH:Aeronautics–Technologicalinnovations.|Aerospace engineering.|Sustainabledevelopment.
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Contents
ListofContributors vii
AbouttheEditors ix
AbouttheCompanionWebsite x
1SustainableAviation:AnIntroduction 1
RobertoSabatiniandAlessandroGardi
SectionIAviationSustainabilityFundamentals 29
2ClimateImpactsofAviation 31
YixiangLim,AlessandroGardi,andRobertoSabatini
3NoisePollutionandOtherEnvironmentalandHealthImpactsof Aviation 49
AlessandroGardi,RohanKapoor,YixiangLim,andRobertoSabatini
SectionIISystemsforSustainableAviation 79
4SystemsEngineeringEvolutions 81
AnthonyZanetti,ArunKumar,AlessandroGardi,andRobertoSabatini
5LifeCycleAssessmentforCarbonNeutrality 113 EndaCrossin,AlessandroGardi,andRobertoSabatini
6AirTrafficManagementandAvionicsSystemsEvolutions 145
AlessandroGardi,YixiangLim,NichakornPongsakornsathien,RobertoSabatini, andTrevorKistan
7OptimisationofFlightTrajectoriesandAirspace 165
AlessandroGardi,YixiangLim,andRobertoSabatini
SectionIIIAerostructuresandPropulsiveTechnologies 213
8AdvancedAerodynamicConfigurations 215
MatthewMarino,AlessandroGardi,RobertoSabatini,andYixiangLim
9LightweightStructuresandAdvancedMaterials 241 RajDasandJoelGalos
10Low-EmissionPropulsiveTechnologiesinTransportAircraft 263 KavinduRanasinghe,KaiGuan,AlessandroGardi,andRobertoSabatini
11ApprovedDrop-inBiofuelsandProspectsforAlternativeAviation Fuels 301
GrahamDorrington
SectionIVResearchCaseStudies 323
12OverallContributionofWingtipDevicestoImprovingAircraft Performance 325
NikolaGavrilovi´c,BoškoRašuo,VladimirParezanovi´c,GeorgeDulikravich,and Jean-MarcMoschetta
13IntegrationofNaturallyOccurringMaterialsinLightweight Aerostructures 343
JoseSilva,AlessandroGardi,andRobertoSabatini
14DistributedandHybridPropulsion:ATailoredDesign Methodology 355
MartinBurston,KavinduRanasinghe,AlessandroGardi,VladimirParezanovic, RaficAjaj,andRobertoSabatini
15IntegrationofHybrid-ElectricPropulsionSystemsinSmall UnmannedAircraft 393
JacobSliwinski,AlessandroGardi,MatthewMarino,andRobertoSabatini
16BenefitsandChallengesofLiquidHydrogenFuelsforCommercial TransportAircraft 417
StephenRondinelli,AlessandroGardi,andRobertoSabatini
17Multi-ObjectiveTrajectoryOptimisationAlgorithmsforAvionicsand ATMSystems 433
AlessandroGardi,RobertoSabatini,andTrevorKistan
18Energy-Optimal4DGuidanceandControlforTerminalDescent Operations 457
YixiangLim,AlessandroGardi,andRobertoSabatini
19ContrailModellingfor4DTrajectoryOptimisation 475
YixiangLim,AlessandroGardi,andRobertoSabatini
20TrajectoryOptimisationtoMinimisetheCombinedRadiativeForcing ImpactsofContrailsandCO2 499
YixiangLim,AlessandroGardi,RobertoSabatini,andTrevorKistan
21TheWLifeCycleModel–SanFranciscoAirportCaseStudy 509
AnthonyZanetti,AlessandroGardi,andRobertoSabatini
22ConclusionsandFutureResearch 517
RobertoSabatiniandAlessandroGardi
Index 523
ListofContributors
RaficAjaj DepartmentofAerospaceEngineering KhalifaUniversityofScienceand Technology,AbuDhabi,UAE
MartinBurston SchoolofEngineering,RMITUniversity Melbourne,Victoria,Australia
EndaCrossin UniversityofCanterbury Christchurch,NewZealand
RajDas SchoolofEngineering RMITUniversity Melbourne,Victoria,Australia
GrahamDorrington SchoolofEngineering RMITUniversity Bundoora,Victoria,Australia
GeorgeDulikravich FloridaInternationalUniversity Miami,Florida,USA
JoelGalos DepartmentofMaterialsEngineering CaliforniaPolytechnicStateUniversity SanLuisObispo,CA,USA
AlessandroGardi DepartmentofAerospaceEngineering KhalifaUniversityofScienceand Technology,AbuDhabi,UAE
NikolaGavrilovi´c ISAE-SUPAERO UniversityofToulouse Toulouse,France
KaiGuan RMITUniversity Bundoora,Victoria,Australia
RohanKapoor SchoolofEngineering RMITUniversity Bundoora,Victoria,Australia
viii ListofContributors
TrevorKistan ThalesAustralia Melbourne,Victoria,Australia
ArunKumar SchoolofEngineering RMITUniversity Bundoora,Victoria,Australia
YixiangLim AgencyforScience,Technologyand Research(ASTAR)
Singapore
MatthewMarino SchoolofEngineering RMITUniversity Bundoora,Victoria,Australia
Jean-MarcMoschetta Jean-MarcMoschettaAerodynamics EnergeticsandPropulsionDepartment ISAE-SUPAEROToulouse,France
VladimirParezanovi´c DepartmentofAerospaceEngineering KhalifaUniversityofScienceand Technology,AbuDhabi,UAE
NichakornPongsakornsathien SchoolofEngineering RMITUniversity Bundoora,Victoria,Australia
KavinduRanasinghe InsitecPtyLtd Melbourne,Victoria,Australia
BoškoRašuo FacultyofMechanicalEngineering UniversityofBelgrade Belgrade,Serbia
StephenRondinelli RMITUniversity Melbourne,Victoria,Australia
RobertoSabatini DepartmentofAerospaceEngineering KhalifaUniversityofScienceand Technology,AbuDhabi,UAE
JoseSilva SchoolofEngineering RMITUniversity Melbourne,Victoria,Australia
JacobSliwinski RMITUniversity Bundoora,Victoria,Australia
AnthonyZanetti RMITUniversity Melbourne,Victoria,Australia
AbouttheEditors
RobertoSabatini isaProfessorofAerospaceEngineeringatKhalifaUniversityofScience andTechnology(UAE)andanHonoraryProfessorofAerospaceEngineeringandAviation atRMITUniversity(Australia).Previously,Prof.SabatiniwasalsoaffiliatedwithCranfield University(UK),whereheledtheresearchteamcontributingtotheEuropeanUnion CleanSkyJointTechnologyInitiativeforAeronauticsandAirTransport–Systemsfor GreenOperationsIntegratedTechnologyDemonstrator.Prof.Sabatiniholdsvarious academicqualificationsinaerospaceandgeospatialengineering,includingaPhDfrom CranfieldUniversityandaPhDfromtheUniversityofNottingham.Additionally,he holdsthelicensesofprivatepilot,flighttestengineerandremotepilot.Throughouthis career,Prof.Sabatinilednumerousresearchprojectsfundedbynationalgovernments, internationalorganizationsandaerospace/defenceindustrypartners.Hehasauthored, co-authored,oreditedseveralbooks,andhashadmorethan300articlespublishedin refereedinternationaljournalsandconferenceproceedings.Since2019,hehasbeenlisted bytheStanfordUniversity’srankingamongthetop2%mostcitedscientistsgloballyin thefieldofaerospaceandaeronautics.Prof.SabatiniisaFellowoftheRoyalAeronautical Society(RAeS),theRoyalInstituteofNavigation(RIN),theInstitutionofEngineers Australia(IEAust),andtheInternationalEngineeringandTechnologyInstitute(IETI), aswellasaSeniorMemberoftheAmericanInstituteofAeronauticsandAstronautics (AIAA)andtheInstituteofElectricalandElectronicsEngineers(IEEE).Hewasconferred prestigiousnationalandinternationalawards,including:Best-in-fieldNationalScientist inAviationandAerospaceEngineering–TheAustralianAnnualResearchReport(2021); DistinguishedLeadershipAward–Aviation/AerospaceAustralia(2021);Scientistofthe Year–AustralianDefenceIndustryAwards(2019);ScienceAward–SustainableAviation ResearchSociety(2016);andArchT.ColwellMeritAward–SocietyofAutomotive Engineering(2015).Since2017,Prof.SabatinihasrepresentedtheAustralianGovernment inseveraloccasionsattheICAOCommitteeonAviationEnvironmentalProtection (CAEP)ImpactandScienceGroup(ISG).Morerecently,hehasalsocontributedtothe activitiesoftheJointAuthoritiesforRulemakinginUnmannedSystems(JARUS),the ICAODroneEnableinitiative,theFAANextGenTechTalkprogram,andtheNASAUAS TrafficManagement(UTM)andAdvancedAirMobility(AAM)workinggroups.Currently, heservesasDistinguishedLectureroftheIEEEAerospace&ElectronicSystemsSociety (AESS),ChairoftheAESSAvionicsSystemsPanel(ASP)andmember-at-largeofthe AESSBoardofGovernors.Additionally,heisafoundingEditoroftheIEEEPressSeries
onAeronauticsandAstronauticsSystems,EditorforProgressinAerospaceSciences, andAssociateEditorforAerospaceScienceandTechnology,Robotica,theJournalof Navigation,andtheIEEETransactionsonAerospaceandElectronicSystems.
AlessandroGardi isanAssistantProfessorinAerospaceEngineeringatKhalifa UniversityofScienceandTechnology(UAE),withmorethantenyearsofexperience inaerospacesystemsresearchandeducation.HereceivedhisBScandMScdegreesin AerospaceEngineeringfromPolitecnicodiMilano(Italy)andaPhDinthesamefield fromRMITUniversity(Australia).Hisworkfocussesonavionics,airtrafficmanagement, andsustainableaviationtechnologyforconventionalandautonomousaerospacevehicles. Inthisdomain,hespecializesinmultidisciplinaryandmulti-objectiveoptimizationwith emphasisonoptimalcontrolmethodsandArtificialIntelligence(AI)techniquesforair andspacevehicledesignandoperations.BeforejoiningKhalifaUniversity,DrGardiwas affiliatedwithCranfieldUniversity(UK)asamemberoftheSystemsforGreenOperations IntegratedTechnologyDemonstrator(SGO-ITD)oftheEuropeanUnionCleanSkyJoint TechnologyInitiativeforAeronauticsandAirTransport,oneofthelargestprograms addressingaviationsustainabilityglobally.Successively,hewasawardedamulti-year ThalesresearchfellowshipinAustralia,duringwhichhecontinuedandextendedhis researchworkonsustainableanddigitalaviationtechnologies.Morerecently,DrGardi hasworkedonadvancingsystemsandsoftwareengineeringmethodologiesforthedesign ofaerospaceanddefencehuman-machinesystems,utilizingneurophysiologicaland systemintegritymonitoring,InternetofThings(IoT)technologyandcyber-resilience functionalitiestooperateautonomouslyforextendedperiodsoftimeevenindegraded conditions.Thesecontributionsalsoresultedinhimbeingconferredthe2020Early CareerAwardbytheIEEEAerospaceElectronicsSystemsSociety(AESS),aswellasinhis appointmentasmemberoftheJointAuthoritiesforRulemakinginUnmannedSystems (JARUS)AutomationWorkingGroupandoftheAESSAvionicsSystemsPanel(ASP).To date,Dr.Gardihasbeenaseniorinvestigatorinmorethantenresearchprojectsfundedby industryandgovernmentpartners,andhasproducedmorethan150refereedpublications. InadditiontohisprimaryaffiliationatKhalifaUniversity,Dr.GardiisanAssociateof RMITUniversityandservesaseditorandreviewerforseveralhigh-impactjournals.
Thisbookisaccompaniedbythefollowingwebsite: www.wiley.com/go/sustainableaviation
Thiswebsiteincludescolorversionofselectedfigures.
SustainableAviation:AnIntroduction
RobertoSabatiniandAlessandroGardi
DepartmentofAerospaceEngineering,KhalifaUniversityofScienceandTechnology,AbuDhabi,UAE SchoolofEngineering,RMITUniversity,Melbourne,Victoria,Australia
Theaviationindustryplaysanimportantroleintheglobaleconomy.Beforetherecentcrisis causedbytheCoronavirusDisease2019(COVID-19)pandemic,airtransportalonecontributedUS$2.7trilliontotheworldGDP(3.6%)andsupported65.5millionjobsglobally[1]. Forseveraldecades,thesectorhasbeenonanalmostuninterruptedexponentialgrowthtrajectory,whichdemonstratedaremarkableresiliencetoeconomicandgeo-politicalcrises. AccordingtoforecastspredatingtheCOVID-19pandemic,airtrafficwasexpectedtodouble approximatelyevery25years[2].Itwasalsoexpectedthatwithoutintervention,aviation wouldcontributeabout6-10%ofallhuman-inducedclimatechangeby2050[3],whilehalf ofallairtrafficwouldtakeoff,land,ortransitthroughtheAsia-Pacificregion.Intheperiod 2019–2020,theCOVID-19pandemichasledtoareductioninglobalpassengertrafficin theorderof60%(2,703millionpassengers)andtheairlinesexperiencedalossofapproximatelyUS$372billionofgrosspassengeroperatingrevenues[4,5].Thesituationgradually improvedin2021and2022,witharecoveryofabout11%and31%inthenumberofpassengers,reflectedbyrevenuelossesofaboutUS$324billionin2021andUS$175in2022 (comparedto2019).
Whilesendingthisbooktothepress,COVID-19travelrestrictionshavebeenremoved inmostregionsandthelatestreportsoftheInternationalCivilAviationOrganization (ICAO)showthatbothdomesticandinternationalairtravelareresumingpre-pandemic levels[5–7].Factorsthatcouldcontributetoacceleratefurthertheaviationmarketrecoveryandgrowthinclude:(1)anincreasingdemandforcommercialUnmannedAircraft Systems(UAS)andAdvancedAirMobility(AAM)services;(2)technologicaladvancesin eco-friendlydesignsolutions(i.e.,aerospacevehicles,propulsion,digitalflightsystems andground-basedinfrastructure);(3)uptakeofsustainableaviationtechnologiesand associatedevolutionsoflegalframeworks,design/certificationstandardsandoperational procedures.Inthelongerterm,theexpansionofcommercialaviationoperationsabove FlightLevel6-0-0(FL600)andtheintroductionofpoint-to-pointspacetransportcould alsocontributetoafurtherevolutionandexpansionoftheaviationsector[8,9].Factors thatcouldhinderthegrowthoftheaviationsectorincludeairlines’bankruptcy,order cancellations,increasedcyberthreats,insufficientinvestmentinaviationinfrastructure,
SustainableAviationTechnologyandOperations:ResearchandInnovationPerspectives,FirstEdition. EditedbyRobertoSabatiniandAlessandroGardi. ©2024JohnWiley&SonsLtd.Published2024byJohnWiley&SonsLtd. CompanionWebsite:www.wiley.com/go/sustainableaviation
increasinggeopoliticaltensions,escalationofconflicts,andglobalrecession,manyof whicharebeingobservedinthepostpandemicera.
Overtheyears,theconcomitanceofseveraleconomic,technologicalandenvironmental factorshasputthesectorunderintenseandgrowingpressure.Keyfactorsincludethe risingcostsofoperationsandfuels;aspikingglobalcompetitioninrelationtotherapid liberalisationofthemarketandtheproliferationofalternativeformsofhigh-speedtransport;increasedairtraffic;capacitybottlenecksatmajorairports;theneedtoreducethe environmentalimpactandachievegreatersustainabilityinairportandaircraftoperations; aswellasnewregulationsandprocessestocaterfornewgenerationaircraftthatare technologicallymorecomplexandhavenewmaintenancerequirements.
Toensuretheaviationsectorcontinuestoplayavitalroleinsupportingeconomicdevelopmentandemploymentworldwide,thefutureairtransportationsystemneedstobecome evenmorecustomer-orientated,timeandcost-efficient,secure,andenvironmentallysustainablethanitistoday.Oneofthemainprioritiesforthesectoristherapiduptakeofdigital technologyand,inparticular,Cyber-PhysicalSystems(CPS)thatcansupporttheintroductionofhigherlevelsofautomation,increasedairspacecapacity,andsignificantadvances inenvironmentalsustainabilityofbothpassengerandcargoairtransportoperations.From theenvironmentalsustainabilityperspective,overthepasttwodecades,variouscountries havesetunprecedentedperformancetargetsforfutureairtransport,suchasgreenhousegas emissionshavingtohalveby2020(relativeto2000)andbecompletelyoffsetby2050[10]. Addingtothesedemandsaretherisingfuelcosts,whichhaveincreasedfourfoldinthepast 20years,impedingtheprofitabilityofbothlargeairlinesandsmalleraviationcompanies.
1.1SustainabilityFundamentals
IntegratingEnvironmentalSusitainability(ES)intobusinessmodelsandassociated businessfunctionsisanopenchallengefacedbymanyindustrysectors,including aviation.ThereisnouniversallyaccepteddefinitionforESwhileathematicsearchof theexistingliterature1 showsaprevailingemphasisontheresponsibleinteractionwith theenvironmenttoavoiddepletionordegradationofnaturalresourcesandallowfor long-termenvironmentalqualitybothlocallyandglobally.Untilrecently,businesseshave notbeenheldaccountableforthecostofdamagesmadetotheenvironmentandsociety. Onepossibleapproachistoquantifytheenvironmentaldegradationcausedbyasector andtherequiredmeasuresforrestoringthepre-existingconditions.Thedamagesand restorationcostsincludevarioussector-specificcontributingfactors.However,inmost cases,suchcostsareassociatedair/land/seapollutionandnoise.Asproposedby[11], thefollowingequationcouldbeusedtoquantifythecostofenvironmentaldegradations causedbyeconomicdevelopmentactivities:
EDT = N × GN × EDG (1.1) where EDT isthetotalenvironmentaldegradation(indollars), N isthepopulation(total numberofpeople), GN istheGrossNationalProduct(GNP)percapita(indollars)and EDG istheenvironmentaldegradationperunitofGNP.
1Thematicsearchon“EnvironmentalSustainability”.Source: ScienceDirect (https://www.sciencedirect .com/topics/agricultural-and-biological-sciences/environmental-sustainability).
So,accordingtoEq.(1.1),anincreaseinpopulationwouldrequireaproportionalreductionoftheenvironmentaldegradationperunitofGNPinordertomaintaintheoverall environmentaldegradationatthesamelevel.Similarly,agrowthoftheGNPpercapita wouldrequireacommensuratereductionoftheenvironmentaldegradationperunitof GNP.However,inpractice,thisequationfindsalimitedapplicabilityasitdoesnotcapturetheneedforabalancebetweenenvironmentalimpactsandthesocialbenefitstobe obtainedbyeconomicdevelopment[12].EffortstoaddresstheselimitationsofearlyquantitativeapproacheshaveplacedemphasisontheconceptofSustainableDevelopment(SD). TheUnitedNation(UN)1987BruntlandReport2 [13]describesSDas: “Developmentthat meetstheneedsofthepresentwithoutcompromisingtheabilityoffuturegenerationstomeet theirownneeds.”
TheconceptsofsustainabilityandSDhavebeensubjectsforextensiveresearchandpoliticaldebateformmanyyears.Whatissustainablecanbeillustratedusingtheso-calledTriple BottomLine(TBL)orthe“ThreeSpheresofSustainability”conceptoriginallyintroduced by[14].AmodernreinterpretationofthisconceptisshowninFigure1.1.
OneoftheadvantagesoftheTBLapproachisthatitrecognisestheimportanceof deliveringsustainableeconomicvaluetoshareholdersbyfocusingonthebottomline profitthatisgenerated.Italsoconsidersthatifanenterpriseistobesustainable,italso needstoevaluateitsperformanceintermsofthecorrespondingenvironmentalandsocial bottomlines[15].SeveralvariantsoftheTBLmodelhavebeenproposedbutessentially thisremainsavalidhigh-levelreferencestillutilisedincurrentresearchworkaddressing thedevelopmentofSBMinthecorporateenvironment.Theconceptsofcorporatesocial
Socio‐Environmental Measures
• Environmental policy
• Environmental laws/regulations
• Natural resources stewardship
• Social awareness and action
Natural resources use
Pollution prevention
Recycling processes
Waste management
Noise reduction
Enviro‐Economic Measures
• Energy efficient design/operations
• Incentives for renewable energy
• New professions/job creation
• R&D investment
Health
Wellbeing
Security
Safety
Education
Community
Inclusion
Socio‐Economic Measures
• Business ethics and integrity
• Fair trade arrangements
• Communication/marketing strategy
• Workforce rights
Figure1.1 Thethreespheresofsustainability.Inspiredby[14].
2In1987,theWorldCommissiononEnvironmentandDevelopment(WCED),publishedareportentitled “Ourcommonfuture”.Thedocumentcametobeknownasthe“BrundtlandReport”afterthe Commission’schairwoman,GroHarlemBrundtland.Itdevelopedguidingprinciplesforsustainable developmentanditisstilladoptedtodayasakeyreferenceinthesector.
responsibilityandenvironmentalaccountabilityhavebeenwidelydiscussedintheliterature[16,17].ThemainfunctionoftheTBLapproachistomakecorporationsawareof theenvironmentalandsocialvaluestheyaddordestroyintheworld,inadditiontothe economicvaluetheyadd[18–20].
Overtheyears,TBLhasbecomeadominantapproachintermsofcorporatereporting [21,22]andcompaniesadoptingTBLreportinghaveintroducedsignificantchangesto thewaytheydo,oratleastthinkabout,business[23].Thethreemajorcriticismsofthe TBLapproachareinitsmeasurementapproach,itslackofintegrationacrossthethree dimensionsanditsmainfunctionasacompliancemechanismratherthanabasisforthe developmentofSBM[24].Totackletheselimitationsandthegrowingneedformorespecificapproachesapplicabletodifferentindustrysectors,researchershaveproposedvariousapproachestoSBM(orbusinessmodelsforsustainability).However,earlyattempts todevelopandintroduceSBMdesignmethodologieswherehinderedbyastrongfocuson compliance(withexistinglawsandregulations)andresponsiblemanagement(i.e.,achievingsomekindofperceivedormeasurableoptimalbalanceinthesocio-economicaldimension).Almostinvariablytheseearlyresearchersconcludedthatmoredetailedinvestigations wereneededtoassesswhetherSBMcouldhelpdevelopingintegrativeandcompetitive solutionsbyreducingnegativeand/orcreatingpositiveexternaleffectsforthenaturalenvironmentandsociety[25–28].
Theseapproacheslimitedtheimpactofthisbodyofresearchandlargelyoverlooked thehugetransformativepotentialofSBMthatintroducenewmechanismsforcommercial valuecreationandvaluecapturebothinternallyandexternallytoaparticularenterprise. Recentresearchhasaddressedtheselimitationsanddevelopedmoreholisticapproaches toSBMdevelopment.Geissdoerferetal.(2016)definesaSBMas: “Asimplifiedrepresentationoftheelements,theinterrelationshipbetweentheseelements,andtheinteractionswithits stakeholdersthatanorganisationalunitusestocreate,deliver,capture,andexchangesustainablevalue.” Themainideapursuedhereistoradicallymodifytheconventionalapproach tobusinessmodellingbyembeddingsustainabilityintothevaluechainsofanorganisation [29].ItisnowacommonviewthatthetransitiontowardsSBMrequiresthepractitionersto lookbeyondthespecificboundariesofanorganisation,anditrequiresinnovationactivities tocreatesustainablevaluesforthestakeholders[30].
SustainableDevelopment(SD)inaviationistypicallymappedtothefollowingfundamentalconcepts[31,32]:
● Theconsumptionofnaturalresourcesismanagedataratewhichallowsfuturegenerationstomeettheirneedsaswellaswedo–i.e.,usageratesofrenewable(e.g.,biofuels) shouldnotexceedtheratesoftheirregeneration,andtheusageratesofnon-renewable resources(e.g.,petroleumfuel)shouldnotexceedthedevelopmentrateoftheirsubstitutes(e.g.,biofuels).
● Thegrowthofaviationsupportsaliveableenvironmentforfuturegenerations–i.e., theratesofpollutingemissionsshouldnotexceedtheassimilativecapacityoftheenvironmentandtheaircraftnoiseexposure(perceivednoiselevelsbythepopulationand frequencyofnoisedisturbanceorawakeningevents)shouldnotleadtoadegradedhealth andqualityoflife.
AsillustratedinFigure1.2,thethreefundamentalcomponentsinsustainableaviation aretheaircraft,theairportandtheAirTrafficManagement(ATM)systems.
Figure1.2 Thethreepillarsofsustainableaviationresearchandinnovation.
Designing/upgradingtheaircrafttobemoreaerodynamicallyandoperationallyefficient entailsadvancesinthefollowingareas:
● Propulsionandpower: targetingimprovementsinfuelefficiency,atransitiontomore sustainableenergymanagementtechnologies,withassociatedreductionsingaseousand noiseemissions.
● Aerodynamics: targetingdragreductionandconsequentialimprovementofaerodynamicefficiencyinvariousflightconditions,aswellasreductionsinairframenoiseand waketurbulence.
● Navigationandguidance: leadingtooptimisedflightpathsforreductionsingaseous andnoiseemissions.
● Computing,informationandcommunication: leadingtomoreefficientmanagementofon-boardsystemsaswellasmorecollaborativeandhigherlevelsofdecision making,supportingmoreeffectiveflightplanningandoperations.
● Structuralmechanicsandmaterials: targetingweightreductionacrosstheaircraft, aswellaslowerimpactsfromthedisposalprocesses.
ATMplaysanimportantroleisdevelopingsystemsandprocedurestosupportefficient useofairspaceandnetworkingbetweenthevariousstakeholders.Thesesolutionsenhance theefficiencyandeffectivenessofflightoperationsbyincreasingthelevelofautomation, improvingthedecision-makingprocessandtargetingtheintroductionofsafety/security measures.Themostpromisingtechnologiesinclude[33]:
● Communication,NavigationandSurveillance (CNS)systemsenabling4DimensionalTrajectory(4DT)basedoperations.
● ATMsystemssupporting4DTPlanning,NegotiationandValidation (4-PNV)with theNextGenerationofFlightManagementSystems(NG-FMS)on-boardaircraft.
AirportsalsoplayafundamentalroleintheSDofaviation.Designing/upgradingtheairportinfrastructureandoperationstobemoreenvironmentallyfriendly,entailstheadoption ofvariousmeasures,suchas:digitaltechnologyandmultimodaltransformation;operationalproceduresandrestrictions[34];landplanningandmanagement;financialmeasures(e.g.,noiseandatmosphericpollutioncharges);measuringandcollectingdata(on noiseandpollutants);preventing/containingfuelandde-icingspillages;andmanagingthe impactonwildlife[35].
Despitetheexistenceofmultipleinterrelatedsocio-technicalfactors,theairtransport literaturediscussesthetopicofsustainabilityadoptingarelativelynarrowperspective andheavilyfocussingonreducingcompliancecostsorbetterutilisingtheexistingairline/airportinfrastructuretoincreaseefficiency/qualityofserviceandrevenues.Other importantsustainabilityfactors(atailoreduptakeofkeyaircraft/ATMtechnologies, airport“greening”andmultimodaltransformation,properdisposal/recyclingofaircraft partsandconsumables,etc.)havetypicallyreceivedlessattentionintheaviationpolitical debate,despitethesignificantbodyofresearchpublishedinthescientificandtechnical literature[12,31,33,34,36].Asaresultofthis,theregulatoryinitiativesledbyICAO andothernational/internationalaviationauthoritieshavebeenrelativelylimitedinthese sectors.Differentmodelsareusedtodescribetheprocessesoccurringintheatmosphere. Uncertaintiesinpredictionscanbeattributedto[37]:
● Theprocessesbeingmodelled(missingorincorrectprocesses).Sinceourunderstanding oftheatmosphericphysicsimprovesovertime,theseuncertaintiescanalsoreduce.
● Differentfactorsinfluencingclimatechange.Uncertaintiesinaviationdevelopmentsalso makeitdifficulttopredicttheimpactofaviationonclimatebeyond5to10years.
Factorsconsideredinpreviousresearchinclude:
● Costofairtravel(andhencenumberofaircraftinoperations);
● Economicactivityandnewmarketopportunities;
● Airtransportliberalizationandsubsides;
● Improvementsinaircraftfuelefficiency;
● Improvementsinengineefficiency.
Toreducetheimpactofaviationontheenvironment,itisclearlynecessary,firstand foremost,toreducetheaircraftemissions.Neweraircrafthaveimprovedfuelefficiency, leadingtoreducedemissions.However,duetothegrowthofairtrafficvolume(expectedto doubleevery20years),theseimprovementsarenotsufficienttobalancetheenvironmental impactofaviation.
1.2InternationalPolicyFramework
TheestablishmentofaninternationalpolicyframeworkwithintheUNallowstechnologicalimprovementsandoperationalchangestobeimplementedthroughpolicydocuments, technical/operationalstandards,recommendationsandeconomicmeasures,whichare typicallytranslatedintolegislation/regulationsbynationalgovernments.Thisprovidesan opportunityforpolicymakers,scientistsandindustrytocommunicateandbetterassess thecostsandbenefitsofimplementingdifferentmeasures.Additionally,theexistenceof
aninternationalframeworkprovidesassurancetoproducersandconsumersthatadopt newtechnologiesandoperationalmeasures,allowingforacoordinateduseofpolicy instrumentstoreduceenvironmentalimpactsandtoincreasethecost-effectivenessofthe variousmitigation/adaptationmeasures.Thecurrentpolicyframeworkincludes:
● UNFrameworkConventiononClimateChange(UNFCCC): aninternationaltreaty addressingclimatechange,originallysignedattheUNConferenceonEnvironmentand Development(UNCED)in1992.TheUNFCCCseeksforthestabilizationofGreenhouse Gasses(GHG)concentrationsintheatmosphereatalevelthatwouldpreventdangerous anthropogenichuman-inducedinterferencewiththeEarth’sclimatesystem.Suchalevel shouldbeachievedwithinatimeframesufficienttoensureecosystemstoadaptnaturally toclimatechange,toensurethatfoodproductionisnotthreatenedandtoalloweconomic developmenttoproceedinasustainablemanner.
● IntergovernmentalPanelonClimateChange(IPCC): ascientificandintergovernmentalbodyaddressinghuman-inducedclimatechange.TheIPCCwasoriginally establishedin1988bytheWorldMeteorologicalOrganisation(WMO)andtheUNEnvironmentalProgramme(UNEP)andwaslaterendorsedbytheUNGeneralAssembly. IPCCdoesnottypicallyconductitsownoriginalresearchbutinsteadperformsdetailed reviewsoftheexistingbodyofscientificknowledge,whicharepubliclydisseminatedin theformofcomprehensiveimpactassessmentreports.
● InternationalCivilAviationOrganization(ICAO): aspecializedagencyoftheUN responsibleforharmonizingtheinternationalpolicies,standardsandpracticesconcerningaviation.TheCommitteeonAviationEnvironmentalProtection(CAEP)isatechnical committeeofICAO,responsibleforassessingandformulatingspecificstandardsandrecommendationsrelatedtoaviationandtheenvironment.
Cost-BenefitAnalysis(CBA)hasbeenwidelyadoptedtoassesstheeffectsof(realor projected)environmentalmitigationmeasuresandcanbeausefultooltoguidepolicydecisions,butcanbelimitedbyuncertaintiesand/orincorrectassumptionsintroducedinthe analysis[12,34,37].Moreadvancedeconometricanalysistechniques/toolshavebeenintroducedbyCAEPandElasticityofDemand(EOD)hasbeenwidelyusedbyindustrytoassess theresponsivenessofconsumerstoairfareincreases(i.e.,howcostincreasesduetonew policiesarepassedtoconsumersandsubsequentlyaffectdemandforaviationservices).
Deregulationoftheairlineindustryhasbecomeapredominanttrendinvarious markets.Deregulationhasresultedincheaperflightsandmorecompetitioninthe industry.However,deregulationhasalsocontributedtoincreasesintrafficvolume,fuel use,airport/airspacecongestionandnoise[2,37,38].Fuelcostandconsumptionare importantdriversformitigationmeasures.Airlineshavetraditionallyinvestedtheir profitsintoacquiringnewtechnologiesandmoreefficientaircraftforreducingoperating coststhroughmoreefficientuseofaircraft,optimalfleetmixandgreaterengineefficiency.However,itisobservedthattherateofimprovementachievablewithpresently knownaerodynamicandpowerplanttechnologieswillnotallowoffsettingtheprojected airtrafficgrowthpost-COVID.So,thecurrentResearchandInnovation(R&I)trends andopportunitiesidentifydigitalaviationtechnologiesaswellasadvancesinenergy production(inparticularbio-fuels)asthemainpathwaystomitigatingtheenvironmental impactofaviation[12,33,39].
ICAOhasbeenthemainregulatorydriverinmodernisingCommunication,Navigation, Surveillance(CNS)forATMandavionicssystemsbutthefocus,sofar,hasbeenalmost exclusivelyonincreasingefficiency(andsafety)oftheairtransportationsystem.This, unfortunately,hasnotyettranslatedinsuccessfulworldwidecooperationefforts.Despite theambitionstargetssetbylarge-scaleregionalR&IprogramssuchasSESAR(Single EuropeanSkyATMResearch)andNextGen(NextGenerationAirTransportManagement), itappearsthattheimpactoftheseUSandEUinitiativeshasbeenhinderedbyanumber ofcontributingfactorsand,sofar,theyhavenotdeliveredtotheirpromises,[40].The situationisevenmorefragmentedintheAsia-Pacificregionthat,beforeCOVID-19,was thefastestgrowingaviationmarketintheworld[41].
Variouspotentialeconomicinstrumentshavebeenproposedovertheyearsandmanyof themhavebeenexperimentedorintroducedinvariousnations.Theseinstrumentsinclude:
● Fueltaxesandchargestopromotefuelefficiencyandreducedemand;
● Emissionschargesaimedatencouragingtheadoptionofloweremittingtechnology;
● Emissionstradingtoencourageemissionsreductionsthroughmarketforces;
● Leviesonemptyaircraftseatstopromoteimprovementinseatloadfactor;
● Leviesonexcessivetrafficperdestinationservedortypeofequipmentservinga destination;
● Leviesonroutelengthtoreducethenumberofflightsexceedingtheminimumdistance;
● Subsidiesorrebatestoactasanincentiveforpolluterstochangetheirbehaviour,suchas grants,softloans,taxallowancesordifferentiation,andinstrumentssimilartoeffluent, product,oradministrativecharges.
Otherinstrumentsidentifiedincludedvoluntarymeasures(e.g.,carbonoffsetting)and multi-modaltransport(e.g.,encouragingrailinplaceofairtransport).
1.3SustainabilityAgenda
Asdiscussedabove,CAEPisatechnicalcommitteeofICAOthatassiststhenationsinformulatingnewpolicesandadoptingnewStandardsandRecommendedPractices(SARPs) relatedtotechnologies/operationsthatreduceaircraftnoiseandGHG/noxiousemissions, andmoregenerallymitigateandkeepsundercontroltheaviationenvironmentalimpacts.
CAEPundertakesspecificstudiesasrequestedbyICAO.Itsscopeofactivitiesencompasses theassessmentofaircrafttechnology,operationalimprovement,market-basedmeasures andalternativefuels.CAEPhasthefollowinghigh-levelgoals:
● Tolimitorreducethenumberofpeopleaffectedbysignificantaircraftnoise;
● Tolimitorreducetheimpactofaviationgreenhousegasemissionsontheglobalclimate;
● Tolimitorreducetheimpactofaviationemissionsonairqualityandwater/land contamination.
CAEPiscomposedbyfourpermanentworkinggroupsandsixdedicatedtask/support groupsasillustratedinFigure1.3.CAEPWorkingGroup1(WG1)addressesaircraft noisetechnicalissues.ThemainaimofWG1istokeepinternationalaircraftnoise certificationstandards(Annex16,VolumeI)up-to-dateandeffective,whileensuringthat thecertificationproceduresareassimpleandinexpensiveaspossible.WG2addresses
Doc9889–Airport AirQualityManual
Doc.9184–Airport PlanningManual
ProcedureforNoise
Figure1.3 CAEPorganisationchart.Source:ICAO(https://www.icao.int/environmental-protection/pages/caep.aspx).
Annex16,Vol.II–AircraftEngine Emissions
Annex16,Vol.III–AeroplaneCO2 Emissions
Annex16,Vol.IV-Carbon OffsettingandReduction SchemeforInternational Aviation(CORSIA)
Annex 16, Vol IV - C Offsetting and Redu Scheme for Internat Aviation (CORSIA
aircraftnoiseandemissionsissueslinkedtoairportsandoperations.WG3dealswith aircraftperformanceandemissiontechnicalmatters,includingtheupdatingofAnnex 16–VolumeIIandthedevelopmentofthenewaircraftCO2 Standard,Annex16–Volume III.TheModellingandDatabasesGroup(MDG)carriesoutmodellingeffortstosupport theactivitiesoftheotherCAEPgroupsandmaintainsvariousdatabasessuchasthe movements,fleetandpopulationdatabases.TheForecastingandEconomicAnalysis SupportGroup(FESG)hastheimportantroleofdevelopingandmaintainingthemodels anddatabasesnecessarytoperformeconomicanalysisandforecastingfleetgrowth.It providessupporttotheotherworkinggroupswithinCAEPandworkswiththemondata issuesthatconcernmorethanoneworkinggroup.
TheAviationCarbonCalculatorSupportGroup(ACCS)hasthetaskofdevelopingand updatinganimpartial,transparentmethodologyforcomputingtheCO2 emissionsfrom passengerairtravel.TheImpactsandScienceGroup(ISG)iscomposedofacademics, scientistsandengineersresponsibleforinformingtheCAEPSecretariatonscientific findings(atmosphericpollutionandnoise)andthemeasuresthattheaviationindustry shouldimplementtolimittheincreaseinglobalaveragetemperaturetolessthan2∘ C abovepre-industriallevels.TheGlobalMarketBasedMeasureTechnicalTaskForce (GMTF)hasamandatetodeveloprecommendationsfortheMonitoring,Reportingand Verification(MRV)systemofinternationalaviationemissionsandforthequalityofoffset remitsforuseinaglobalmarket-basedmeasureforinternationalaviation.TheAlternative FuelsTaskForce(AFTF)assessesthepotentialemissionreductionsattainablefromthe useofalternativefuelsinaviation.
Towardstheendofthe1990’s,theUSandEUstartedaddressingaviationSDasan integralpartoftheirpolicyagendasandinitiatedlarge-scaleR&Iinitiatives.TheEU AdvisoryCouncilforAviationR&IinEurope(ACARE)initiallydevelopedVision2020 and,successivelyFlightPath2050,settingunprecedentedemissionreductiontargets(both forgaseouspollutantsandnoise).Inparallel,theCleanSky(EUFramework7)andClean Sky2(Horizon2020)programswerelaunchedtoaddressaircrafttechnologyevolutions, whiletheATMquotawasassignedtoSESAR.IntheUS,theNASAEnvironmentally ResponsibleAviation(ERA)programaddressedobjectivessimilartoCleanSky/CleanSly 2butwithamuchsmallerbudgetandwithoutprogressingtothehighTechnicalReadiness Level(TRL)requiredintheEUindustry-drivenprograms.TheERAprogramcompleted itsmandatein2016andwasfollowedbytheStrategicImplementationPlan(SIP),which isstillongoingandpursuessimilarobjectivestoEUFlightPath2050(Figure1.4). Someoftheopenquestionsthattheglobalaviationcommunityisfacingare:
● Largeuncertaintiesoverfuturetrendsintraffic,technology,andthereforeemissions, dependingonthescenarios/assumptionsselectedfortheprojections.Keycontributing factorsincludeuncertaintiesaboutthepaceofintroductionofgame-changingtechnologiesandtheimpactsofthecurrentinfrastructureconstraints(“bottlenecks”)inlimiting growthbothinairport/airspacecapacityanddemand.
● Themonetaryimpactofaviationemissionsontheenvironmentandthemonetary benefitsofmitigatingthoseimpacts.Asalreadymentioned,differentmodelsand differentscenarios/assumptionsproducedifferentresultsandthereisnoconsensuson theappropriatelevelatwhichanyenvironmentallevyshouldbeset.
● Astheenvironmentalbenefits(reductionofgaseousandnoiseemissions)achievable withconventionalaircraft/powerplantsconfigurationshavereachedaplateau,itis
A/C
ACARE – SRA and SRIA (vs. 2000) NASA – ERA (vs. 1998) and SIP (vs. 2005)
ACARE ‐ Advisory Council for Aviation R&I in Europe, SRA ‐ Strategic Research Agenda, SRIA ‐ Strategic Research and Innovation Agenda, ERA ‐ Environmentally Responsible Aviation, SIP ‐ Strategic Implementation Plan
A/C ‐ Aircraft, LTO ‐ Landing and Take/Off, CRZ ‐ Cruise, *Below CAEP6, **Below Chapter 4. All % reductions are in Passenger‐km
Figure1.4 Fuel,gaseousemissionsandnoisegoals.
MAPPING OUT THE INDUSTRY COMMITMENTS
Figure1.5
essentialtoinvestigatemoreradicalapproaches.Theseincludeadvancedroute/airspace optimisationtechniquesthroughtheadoptionofnetwork-centricATMandavionics technologies,innovativeaircraft/enginedesignapproachesandalternativeaviationfuel, includingbiofuels.ThisconceptisgraphicallyillustratedinFigure1.5.Althoughthe illustrationreferstoCO2 emissionreductiongoals,similarconclusionshavebeenfound forotherGHGandnoxiousemissions[42].
Additionally,thereislimitedpracticalexperiencewithemissiontaxesandtrading schemesatagloballevelandthereareuncertaintiesregardingtheapplicabilityofmany economicandtechnicalmeasurestocountriesnotincludedintheUNFCCC.
Currentstrategiesforensuringaviationsustainabilityincluderegulatingaircraft design/operationswithenvironmentally-friendlypolicies(carbontax/offsettingschemes, noiseemissioncharges,replacingorruling-outoldfleet,etc.).However,inthelongterm, digitaltransformationinitiativesareessentialandwillradicallytransformproductand servicelifecyclemanagementprocessesbothintheaerospaceandaviationindustries. Suchinitiativeswillinclude:
● AdoptingMultidisciplinaryDesignOptimisationandMulti-ObjectiveMissionOptimisation(MDO/MOMO)toolstodevelopnewCNS/ATMandAvionics(CNS+A)systems foreco-friendlyflightoperations(i.e.,managementofairspace,trajectoryandmission) [33,39,43].
● AdoptingMDOandotherdigitaltools(e.g.,artificialintelligence,roboticprocess automationanddigitaltwins)forDesign,Development,TestandEvaluation(DDT&E) andMaintenance,RepairandOverhaul(MRO)ofmoreenergyefficientand“cleaner” (i.e.,lesspolluting)propulsivesystems[39].
● AdoptingMDOandotherdigitaltoolsforDDT&E/MROoflighterandmoreaerodynamicallyefficientmanned/unmannedaircraft[39].
● Enablingthecost-effectiveintroductionofalternativeaviationfuels,especiallythirdgenerationbiofuels,bydeployingtherequiredCPSarchitectures(e.g.,distributedsensor networksandAI-basedhealth/qualitymonitoring)toimprovecropquality,maximise fuelyieldandminimiselandtake[44].
● DevelopingIntelligentTransportSystems(ITS)formultimodalairporttransformation. Thesewillincludeadvanceddigitalsolutions(e.g.,sensornetworks,user-apps,centralise/distributedtrafficmanagement,connectedautonomousvehicletechnologies) whichaimtoprovideinnovativeservicesrelatingtovariousinterconnectedmodesof transportandenableuserstobebetterinformedandmakesafer,morecoordinatedand “smarter”useofthetransportnetwork[12,45].
However,thereisaneedtoassesstheimpactsofvariouspossiblemeasuresforencouragingtheadoptionofdigital/sustainableaviationtechnologies,includingtheapplicability toaviationofmaturesolutionsand/orpromisingoperationalconceptsdevelopedinother sectors.
1.4EmissionTaxes,TradingandOffsetting
Oneoftheearliestpropositionsbroughtforwardattheonsetoftheglobalwarmingdebate wasataximposedoncompaniesbasedontheamountofemissionstheyproduce,specificallyonGHGssuchasCO2 andwascommonlyknownas“CarbonTax”(CT).CTissimply adirectpaymenttogovernment(collectionbody),basedonthecarboncontentofthefuel beingconsumed.Giventhattheprimaryobjectiveoftheabatementpolicyistolowercarbondioxideemissions,carbontaxesmakesenseeconomicallyandenvironmentallybecause theytaxtheexternality(carbon)directly.
UnderanEmissionTrading(ET)system,thequantityofemissionsisfixed(oftencalleda "cap")andtherighttoemitbecomesatradablecommodity.Thecap(say10,000tonsofcarbon)isdividedintotransferableunits(10,000permitsof1tonofcarboneach).Permitsare oftenreferredtoas"GHGunits,""quotas"or"allowances."Forcompliance,actorsparticipatinginthesystemmustholdanumberofpermitsgreaterorequaltotheiractualemissions level.Oncepermitsareallocated(byauction,saleorfreeallocation)totheactorsparticipatinginthesystem,theyarethentradable.Thisenablesemissionsreductionstotakeplace whereleastcostly.SomekeycharacteristicsofETschemesinclude:
● Theemissionlevelsarespecifiedupfront,allowingmorepredictableestimatesofemissions.Thisalsoallowsforcountriestoagreeuponspecificemissionsreductionlevels, makinginternationalenvironmentalagreementsmorenegotiable.
● Emissionstradingismoreappealingtoprivateindustry,asfirmscanprofitbysellingtheir excessgreenhousegasallowances.Creatingsuchamarketforpollutioncouldpotentially driveemissionsreductionsbelowtargets.
● EmissionstradingisbetterequippedthantaxestodealwithallsixGHGsincludedinthe KyotoProtocolandsinks(e.g.treeswhichabsorbandstorecarbon)inonecomprehensive strategy.Eachgashasa"greenhousegaspotential"(GWP,basedoncarbondioxide).Thus, firmsemittingmorethanoneGHGhavemoreflexibilityinmakingreductions.
● Permitsadjustautomaticallyforinflationandexternalpriceshocks,whiletaxesdonot. Forexample,theUShasalreadyexperiencedanextendedperiodofstablegreenhouse gasemissionslevelsfrom1972to1985becauseofhighoilprices.Taxeswouldneedtobe designedtoadjustforsuchexternalshocks.
ComparedtoET,CTofferabroaderscopeforemissionsreductions,extendingtoall carbon-basedfuelconsumption,includinggasoline,homeheatingoilandaviationfuels.
● Comparedtoemissionstrading,whichinvolvessignificanttransactioncosts,taxes involvelittletransactioncost,overallstagesoftheirlifetime.
● Taxesarenotsusceptibletospeculativeorhoardingbehaviourbyfirmsornongovernmentalorganizationswhichmayharmthemarketforces.
● Comparedtoemissionstrading,whichrelyonthesupplyanddemandofemission permitstocontrolemissions,carbontaxesprovideapermanentincentivetoreduce emissions.Improvementsintechnologyandoperationsmightleadtoreductionsinthe permitprice,loweringtheincentivetoreduceemissions.
● Emissionstradingproposalsarehighlycomplicatedandtechnical,unliketaxeswhichare familiarinstrumentstopolicymakers.Ongoingcostsarealsolowfortaxsystemsbecause ofthelackofmonitoringandenforcementrequirements.
● Emissionstradingmaypreventmeaningfuldomesticreductionsfromtakingplace,as somecountriesmightchoosetobuyemissionpermits.Thisrisessignificantequityissues amongdeveloped,developingandtransitionaleconomies.
● Carbontaxesearnrevenue,whichcanbe"recycled"backintotheeconomybyreducing taxesonincome,labourand/orcapitalinvestment.Permitsystemshavethepotentialto earnrevenue,butonlyifpermitsareauctioned.
Carbonoffsettingallowsindividualsandcompaniestoreducetheircarbonfootprintby investinginenvironmentalprojectselsewhere.Creditsareusuallypurchasedandusedby
individualsorcompaniestocanceloutor“offset”theemissionstheygenerateduringtheir day-to-daylifeornormalcourseofbusiness(e.g.,usingairtransport).Carbonoffsetscanbe usedtooffsetemissionsvoluntarilyortomeetregulatoryrequirements.Carbonoffsetting projectsmayinclude:
● Reducingthecostdifferentialofrenewableenergysuchaswind,solar,hydroelectric powerorbiofuel,therebyincreasingitscommercialviability;
● Combustionorcontainmentofmethanegeneratedbylandfills,industrialwasteorfarm animals–convertingmethanetoCO2 ;
● Increasingtheenergyefficiencyofbuildings,vehiclesorpowerplants;
● Reforestationinitiatives.
In2009,theAirportsCouncilInternationalEurope(ACIEurope)introducedacarbon managementinitiativeforairports,calledthe AirportCarbonAccreditation program,which allowsairportstoberecognised(throughaccreditation)fortheireffortsinmanagingand reducingtheircarbonemissions.Airportscanbeaccreditedtooneoffourlevelsinthe program[46]:
● Level1:Mapping,requiringcarbonfootprintmeasurement;
● Level2:Reduction,requiringacarbonmanagementplantobeinplace;
● Level3:Optimisation,requiringairportstoengagestakeholders(airlines,catering,air trafficcontrol,groundservices,rail,etc.)toreducetheairport’scarbonfootprint;
● Level3+:Neutrality,requiringairportstoneutraliseanyresidualemissionsthrough carbonoffsetting.
Theaccreditationrequiresairportstoverifytheiractivities(e.g.,carbonmonitoringand managementprocesses)byagroupofindependentverifiers.Thecarbonfootprintofan airportisverifiedinaccordancewiththeISO14064standard(GreenhouseGasAccounting), whichrequiresspecificsupportingevidence.
1.5ATMandAvionicsSystems
Inthelasttwodecades,anumberofmajorATMmodernisationinitiativessuchasthe SingleEuropeanSkyATMResearch(SESAR)andtheNextGenerationAirTransportation System(NextGen),werelaunchedaroundtheglobetocopewiththerapidgrowthof airtrafficandmitigatethegrowingcongestionandinefficiencyissues.Theseinitiatives supportanevolutionoftheATMsystemintoahighlyintegratednetworkwherecivil, military,andremotelypilotedaircraftwillcontinuouslyanddynamicallysharethe commonairspaceinahighlyautomatedandcollaborativedecision-makingenvironment. Tomeetthegoalsofenhancedflightsafety,environmentalperformance,andefficiency whilesimultaneouslyaccommodatingthepredictedtrafficgrowth,severalkeypolicy directionshavebeenidentifiedbyvariousgovernmentsinternationally[47]:robustand integratedplanning,adoptionofadvancedtechnology,internationalharmonisationof ATMsystems,enhancedregionalaviationsafety,andenvironmentalimpactmitigation. Inthiscontextonekeystrategicpriorityforcountriesistoplan,develop,andimplement
anewATMplatformthatmeetsthefutureneedsofbothcivilandmilitaryaviationwhile enhancingATMbusinesscompetitivenessbyaddressingservicecapability,continuity, andenvironmentalsustainability[48].Withairtrafficexpectedtogrowmoresubstantiallywithinthelifespanofthenewtransportaircraft,alongwiththeintroductionofnew conceptstoimproveairspaceorganisationandairportoperations,thesemajoraviationrenovationprogrammesaroundtheworldwillplayacriticalroleinthesuccessfultransition tonewtechnologiesandoperationalstandards.Researchisthereforeneededtodevelop anewATMregulatoryframeworkandnewsystemsfordynamicairspacemanagement (DAM),free-flightandintent-basedoperations.Thisalsoencompassesthedevelopment ofinnovativemethodsandalgorithmsforthedynamicallocationofcivil/militaryairspace resourcesandofCNS+Atechnologiesenablingtheunrestrictedaccessofremotelypiloted aerialsystems(RPASs)toallclassesofairspace.
Ground-basedautomaticdependentsurveillancebroadcast(ADS-B)currentlyprovides wideareasurveillancecoverage,includingthosevastregionsoftheplanetthatarenot underprimaryorsecondarysurveillanceradar(SSR)coverage.Areceiverautonomous integritymonitoring(RAIM)systemenablescontrollerstoanticipateandplanforareversiontoproceduralseparationifaGPSoutageispredicted.Forareasthatareunderradar surveillance(majoraircorridorsandterminalmanoeuvringareas)sensor-fusedradar andADS-Bdatahaveprovedtobesuperiortoradardataalone,particularlyfortracking manoeuvringaircraft.Space-basedADS-BpromisestoexpandthebenefitsofADS-Bto oceanicairspaceandaddressesthelowreportingrateofautomaticdependentsurveillance contract(ADS-C).OptimisedATMproceduressuchastailoredarrivals[49]andthe GreenRNPproject[50]havebeentrialledoralreadyimplemented.Agrowingnumberof airport/airlineslotmanagementandAirTrafficFlowManagement(ATFM)centresaround theworldhavecontributedtooptimisestheallocationofairportandairtrafficcontrol (ATC)slots,whiletrafficmanagementinitiatives,suchasgrounddelaysprogrammes, tacklecriticalcongestionsituations,therebysimultaneouslyreducingfuelconsumption, noiseandgaseousemissions.Collaborativedecisionmaking(CDM)proceduresimprove commonsituationalawarenessandpermitpre-tacticalslotswapping.Currentinitiatives includeuserpreferredroutes(UPRs)andtheextensionofnationalCDMandATFM operationstosupportlong-rangeATFMstrategiesforentireworldregions.Conducting ATFMacrossnationalborderswillimproveitseffectiveness,particularlyforcommercial airlinecompanies.Forexample,delaycanbeabsorbeden-routeorallocatedasground delayifcongestionisanticipatedatthedestinationairportseveralFIRsaway.Achieving thisintheAsia-Pacificregionwithoutasingleregulatoryauthority,likeEurocontrolor theFederalAviationAdministration(FAA),isoneoftheissuestobeaddressedbutthe benefitsareevident.EarlyregionalCDMtrialsbetweenBangkokandSingaporehave provedpromising[51],anditisclearthatinteroperabilityandharmonisationofstandards willbekeyfactorsinmovingforward.
InlinewiththeICAO’sASBUimplementationtimelines,newhigh-integrityand safety-criticalCNS+Asystemswillbedevelopedanddeployedforstrategic,tactical,and emergencyATMoperations,andinparticular:
● Civil/militarydual-useCNS+Atechnologies,includingasecureandreliablenetwork infrastructureandairbornedatalinkforinformationsharingandCDM,network-centric
ATMtechnologiesforstrategicandtacticalATFM,DAMandreal-timefour-dimensional trajectory(4DT)operability.
● CNS+AtechnologiesforRPAS,reliablymeetingtherequiredcommunication,navigation,andsurveillanceperformance(RCP,RNP,andRSP)standardsforunrestricted accessofRPAStoairspace(non-segregatedoperations).Inthisperspective,essential stepsaretheadoptionoffusedcooperative/non-cooperativesurveillancesystems, beyondline-of-sight(BLOS)communicationsystems,high-integritynavigationsystems andintegratedavionicsarchitectures.
● Satellite-basedCNSsystems,suchasmulti-constellationglobalnavigationsatellitesystems(GNSS)andspace-baseddatalinkandADS-B,forimprovedcoverageofremoteand oceanicairspace,precisionapproach,andauto-land.
● AirportATMsystems,mainlyconsistingofsafetynetsforgroundandairtrafficoperations,remotetowersystems(RTSs)andnewstandardisedairtrafficcontroloperator (ATCO)workpositions.Inparticular,theadvancedsurfacemovementguidanceandcontrolsystem(A-SMGCS)willalsoproviderunwayincursionandexcursiondetectionand alertingsimilartotheairportmovementareasafetysystem(AMASS)andrunwayawarenessandadvisorysystem(RAAS)developedinEuropeandtheUS.
Anetwork-centriccommunicationapproachisrequiredtoallowgreatersharingofATM information,suchasweather,airportoperationalstatus,flightdata,airspacestatusand restrictions.Keynetworkbuildingblocksincludehigh-integrity,high-throughputand secureavionicsdata-linksfordualcivil/militaryusageaswellasasystemwideinformation management(SWIM)system.Webservicetechnologiesformobile,internet-basedaccess willalsobeincludedtoflexiblyexpandthenumberofparticipantsintheCDMprocesses. BusinessintelligenceandbigdatawillalsobeimplementedaspartofSWIMforenhanced datamining.Theimplementationofenterprise-widedatawarehousesbyANSPswill enableATMtomovebeyondpost-eventreportingandtomineyearsofhistoricaldatato determineunderlyingtrafficflowpatternsandemissionlevelssoastoderiveenhanced modelstoaddressthem.Automatedairtrafficflowmanagement(A-ATFM)systemswill enhancethecontinuousbalancingofair-trafficdemandwithcapacitytoensurethesafe andefficientutilisationofairspaceresources.Automateddynamicairspacemanagement (ADAM)willenabletheseamlessoptimalallocationofairspaceresources.Real-time multi-objective4DToptimisationandnegotiation/validationalgorithms,implemented inthenextgenerationofground-basedandairborneCNS+Asystems,willpromotea continuousreductioninenvironmentalimpacts,whichwillbeparticularlysignificant inseverecongestionandweatherconditions.Toenhancetheoperationalefficiencyat bothregionalandgloballevels,itisessentialtoaddresstheinteroperabilityoftheATM regulatoryframeworkevolutionswithinandacrossregions,preferablytakingthemove fromtheEuropean/USframeworks(beingdefinedbySESARandNextGen).Thiswilllikely contributetotheglobalICAOinitiativesinthisdomain,suchastheAviationSystemBlock Upgrades(ASBUs).Fromatechnologicalperspective,interoperabilityisalsorequiredat variouslevels,includingsignal-in-space(SIS),systemlevelandhuman-machineinterface andinteraction(HMI2 ).
SESAR[10]hasdefinedthreephasesofATMsystemdevelopmentinanevolutionary roadmap,representedinFigure1.6.Thesephasesare:
Figure1.6 Evolutionaryroadmapfor ATMOperations.
Time-Based Operations
Trajectory-Based Operations
Performance-Based Operations
● Time-basedoperations,forwhichATMstrategicandtacticalactions(includingATFM) areaimedatoptimaltrafficsynchronisation.
● Trajectory-BasedOperations(TBO),focussingonafurther-evolvedpredictability,flexibility,andenvironmentsustainabilityofairtraffic,unleashingadditionalcapacity.
● Performance-basedoperations,forwhichalltheavailableCNSperformanceisexploited toestablishahigh-performance,network-centric,collaborative,integrated,andseamless ATMsystem,supportinghigh-densityoperations.
TBOarebasedontheadoptionof4DTdefiningtheaircraft’sflightpathinthree spatialdimensions(i.e.latitude,longitude,andaltitude),andintimefromoriginto destination[52]andoftheassociatedpreciseestimationandcorrectionofcurrentand predictedtrafficpositions.Eachaircraftfollowsa4DT,whichisdeterminedviaaCDM processinvolvingnovelsystems,suchasthenextgenerationflightmanagementsystem (NG-FMS),andevolvingtacticallyfromtheoriginalreferencebusinesstrajectory.Increased efficiencyandhigherthroughputareobtainedinaCNS+Acontextbyactivelymanaging 4DT.InthePBOcontext,thenextgenerationairtrafficmanagement(NG-ATM)services willbematchedtotheperformancecapabilityofaircraft.AirlinesdeployingPBO-capable equipmentwillbenefitfromhigherschedulingpriorityandeasieraccesstocongested areas.Theseregulationswillimposerequirementsintermsofsystemperformancerather thanintermsofspecifictechnologyorequipment.
1.6LightweightStructuresandMaterials
Thecontinuouspushtoreduceweightandenhancemechanicalpropertiesofaerostructureshasledtosignificantadvancesinaircraftdesignandlifecyclemanagementprocesses, asdemonstratedbycontemporaryairlinerssuchastheBoeing787“Dreamliner”andthe AirbusA350ExtraWide-Body(XWB)aircraft.Theseaircraftdeliversubstantialimprovementswhencomparedtopreviousgenerationairliners,largelythroughtheselectiveuse ofnewadvancedmaterialsinvariouspartsoftheairframeandpropulsivecomponents [53,54].Inparticular,theadoptionofcarbonfibrecompositesandotherhybridmaterialshasfacilitatedtheimplementationofmuchlighteraircraftdesignswhileimprovingthe overallmechanicalpropertiesofaerostructures[55].
Lighteraircrafttranslatesintoreducedthrustandfuelconsumption,withassociated enhancementsinpayloadcapacity,rangeandendurance.Additionally,thelowerthrust requirementsallowfortheintegrationofsmaller,lighterandquieterengines,thereby leadingtonoisereductionandfurtherfuelsavings.Openresearchchallengesandopportunitiesincludemethodsforfatiguelifeassessment,maintenanceandtestingofcomposite structures(e.g.,newcompositerepairtechnologiesusinghybridmaterialsystemsand
newnanotechnologiestoimproveadhesivebondingprocesses,thermalpropertiesand lightningprotection);sandwichstructureoptimisationtopreventbucklingandwrinkling ofthesoftcore;net-likeanisogridstructurestoincreasetorsionalrigidityandtherebyavoid flutter;usingnaturalfibresandbinders(e.g.,bamboo,cork,resinsandlatexes)toenhance certainmechanicalpropertiesandrecyclabilityofcompositematerials;andreducingthe production,assemblyandoperatingcostsofcomposites,whicharesignificantlyhigher thanaluminiumalloys.Theglobalcarbonfibremarketisprojectedtogrowfrom$2.33 billionin2021to$4.08billionin2028atacompoundannualgrowthrate(CAGR)of8.3% intheforecastperiod2021-2028[56].Theglobaldemandforcarbonfibreisverylarge andrapidlygrowing.Currently,theproductionandmaintenanceofmodernairliners(e.g., AirbusA380,AirbusA350,Boeing787andBoeing777),requiresapproximately15,000 tonsofcarbonfibreperannum.Thus,withthecurrentratesofproduction(significantly impactedbyCOVID-19),itisprojectedthattherewillbeashortageofsupplytomeet demandinthenearfuture.
1.7AdvancedAerodynamicConfigurations
Intermsofdesign,aircrafthavenowforquitealongtimebeenfollowingaconventional configurationwhichincludesacentralfuselageandamainwing,plushorizontaland verticaltailplanes.Thisconfigurationpresentsafewpracticaladvantagesbutisrather farfromthetheoreticalefficiencylimits,asitreliesonthefunctionalseparationbetween payload-carryingandlift-producingelements.Keylimitationsofthisapproachinclude:
● thefuselageproducingsubstantialdragbutinsignificantlift,whichweighsheavily againstaerodynamicefficiency(i.e.,theratiobetweenliftanddragoftheentireaircraft inrepresentativeoperationalconditions);
● theconcentrationofverysignificantshearstressesandbendingmomentsinsmall sectionsofthewingroot,whichthenhavetobereinforcedadequately,adding substantialstructuralweight;
● naturaltendencytodeveloplargetipvortexes,whichresultinanenergy-dissipatingand operationallyhazardousturbulentwake.
Advancedaircraftconfigurationsattempttoenhancetheaerodynamicefficiencyofthe aircraftinrepresentativeoperationalflightconditions,comparedtoconventionaldesigns. Varioussolutionshavebeenproposedthroughouttheyears,includinghybridwing-bodies (e.g.,blendedwing-body,flyingwing),box-wingaircraftandadvancedmorphingaircraft technologies.Someofthekeygainsinsuchtechnologiesincluderespectivelya30%increase inaerodynamicefficiencyora40%reductionininduceddrag.Despitetherelativelyhigh confidenceinthesetheoreticalefficiencygainsandsomesuccessfuloperationalexperience inthedefencesector,theactualadoptionoftheseadvancedconceptsintheciviltransport domainhasbeenencumberedbythelimitedmaturityofcertaintechnologiesandalukewarmattitudebymajoraircraftmanufacturers,whichadoptedamorerisk-averseapproach financially,resultinginfurtherevolutionsoftheconventionalconfiguration.Morerecently, thediminishingreturnsassociatedwithfurtherinvestmentsinconventionalaerodynamic technologiesiselicitingamorecourageousattitudeinembracingthenewconfigurations.
