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TRANSCRIPT
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WorldMeteorologicalOrganization
AMDAR
ONBOARD
SOFTWARE
FUNCTIONALREQUIREMENTS
SPECIFICATION
FrankTamis
3092012
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RevisionData
REVISIONSTATUS STATUSDATE DESCRIPTION
Draft January17,2012 Originalrelease,skeletondraft
F.C.Tamis,
AircraftDataEngineering&Consultancy
01 April18,2012 FirstConcept
F.C.Tamis,
AircraftDataEngineering&Consultancy
02 May15,2012 SecondConcept
F.C.Tamis,
AircraftDataEngineering&Consultancy
03 September29,2012 CompleteDraft
F.C.Tamis,
AircraftDataEngineering&Consultancy
04 October27,2012 RevisionstocompletedraftbasedonWMOinput.
F.C.Tamis,
Airdatec
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TableofContents
1 INTRODUCTION................................................................................................................. 5
1.1 BACKGROUND....................................................................................................................... 5
1.2 OBJECTIVES .......................................................................................................................... 5
1.3 INTENDEDAUDIENCEANDSCOPE.............................................................................................. 5
1.4 CONVENTIONS ...................................................................................................................... 6
1.5 APPLICABLEDOCUMENTS........................................................................................................ 6
1.6 ABBREVIATIONSANDACRONYMS.............................................................................................. 7
2 AMDARSYSTEMOVERVIEW.............................................................................................. 8
2.1 AMDARSYSTEM .................................................................................................................. 82.2 AMDARONBOARDPROCESS.................................................................................................. 9
2.3 OTHERSPECIFICATIONS......................................................................................................... 10
2.4 FURTHERREADING.............................................................................................................. 11
3 AMDARONBOARDSOFTWAREREQUIREMENTS ............................................................. 12
3.1 DATAACQUISITION.............................................................................................................. 13
3.2 DATAHANDLING ................................................................................................................. 15
3.2.1 Dataacquisitionrate...............................................................................................................15
3.2.2 DataValidation........................................................................................................................16
3.2.3 DataSmoothing ......................................................................................................................16
3.2.4 DerivedParameters ................................................................................................................ 163.2.4.1 PhaseofFlight.................................................................................................................16
3.2.4.1.1 Ground ...................................................................................................................... 16
3.2.4.1.2 Ascent .......................................................................................................................17
3.2.4.1.3 EnRoute ...................................................................................................................17
3.2.4.1.4 Descent .....................................................................................................................17
3.2.4.2 TurbulenceIndicator .......................................................................................................17
3.2.4.3 WaterVapor/RelativeHumidity/DewPoint................................................................17
3.2.4.4 RollAngleFlag.................................................................................................................17
3.2.4.5 AircraftConfigurationIndicator......................................................................................19
3.3 AMDAROBSERVATIONS...................................................................................................... 19
3.4 OBSERVATIONFREQUENCY .................................................................................................... 203.4.1 EnrouteObservations ............................................................................................................20
3.4.1.1 MaximumWindObservation ..........................................................................................20
3.4.2 PressureBasedScheme .......................................................................................................... 21
3.4.2.1 RoutineObservations......................................................................................................21
3.4.2.2 Ascent..............................................................................................................................21
3.4.2.2.1 InitialObservation.....................................................................................................21
3.4.2.2.2 AmbientStaticPressureatTakeOff.........................................................................21
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1 Introduction
1.1 Background
TheGlobalAircraftMeteorologicalDataRelay(AMDAR)ProgramisaprograminitiatedbytheWorld
MeteorologicalOrganization(WMO)incooperationwithaviationpartners,andisusedtocollect
meteorologicaldataworldwidefromcommercialaircraft.TheWMOAMDARObservingSystemisasub
componentoftheWMOIntegratedGlobalObservingSystem,whichisdefinedandmaintainedunder
theWMOWorldWeatherWatchProgram1.
Existingaircraftonboardsensors,computersandcommunicationssystemsareutilizedtocollect,
process,formatandtransmitthemeteorologicaldatatogroundstationsviasatelliteorradiolinks.Once
ontheground,thedataisrelayedtoNationalMeteorologicalServices,whereitisprocessed,quality
controlledandtransmittedontheWMOGlobalTelecommunicationsSystem(GTS).
Thedatacollectedisusedforarangeofmeteorologicalapplications,including,publicweather
forecasting,climatemonitoringandprediction,earlywarningsystemsforweatherhazardsand,
importantly,weathermonitoringandpredictioninsupportoftheaviationindustry.
1.2 Objectives
ThisdocumentprovidesacomprehensivefunctionalspecificationforonboardAMDARsoftware.Itis
intendedthatthespecificationprovidessufficientinformationtoenabledetailedtechnicalspecifications
tobeprovidedforAMDAROnboardSoftwareimplementationonsuitableavionicsplatforms.
1.3 IntendedAudienceandScope
Thespecificationisprimarilyintendedforusebybothmeteorologicalagenciesandavionicssoftware
developerstoallowthemtojointlydevelopAMDARsoftwarewithminimaladditionalinformation.It
definestheFunctionalSpecificationsoftheAMDAROnboardSoftwareonly.FunctionalSpecificationsof
otherpartsoftheAMDARdataflow,suchasgroundbasedprocessing,areoutsideitsscope.
Thespecificationwillbeapplicableforallkindsofonboarddataprocessingandcommunicationssystem
solutions,includingACARSand/orsuccessors.
Bydefinition,anaircraftbasedmeteorologicalobservingsystemthatconformstothisspecification,and
mostparticularlytothoserequirementsthataredesignatedasrequired(seeconventions,paragraph
1.4),canbeconsideredanAMDARobservingsystem.
1TheWMOWorldWeatherWatchProgramme:http://www.wmo.int/pages/prog/www/index_en.html
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1.4 Conventions
Thekeywords"must","mustnot","required","shall","shallnot","should","shouldnot",
"recommended","may",and"optional"inthisdocumentaretobeinterpretedasfollows:
1.ThetermsSHALL,"REQUIRED"or"MUST"meanthatthedefinitionisanabsoluterequirementof
thespecification.
2.ThephrasesSHALLNOTor"MUSTNOT"meanthatthedefinitionisanabsoluteprohibitionofthe
specification.
3.ThetermsSHOULDor"RECOMMENDED"meanthatthere mayexistvalidreasonsinparticular
circumstancestoignoreaparticularitem,butthefullimplicationsmustbeunderstoodand carefully
weighedbeforechoosingadifferentcourse.
4.ThephrasesSHOULDNOT or"NOTRECOMMENDED"meanthattheremayexistvalidreasonsin
particularcircumstanceswhentheparticularbehaviorisacceptableorevenuseful,butthefull
implicationsshouldbeunderstoodandthecasecarefullyweighedbeforeimplementinganybehavior
describedwiththislabel.
5.ThetermsMAYor"OPTIONAL"meanthatanitemistrulyoptional. Onevendormaychooseto
includetheitembecauseaparticularmarketplacerequiresitorbecausethevendorfeelsthatit
enhancestheproductwhileanothervendormayomitthesameitem.Animplementationwhichdoes
notincludeaparticularoptionMUSTbepreparedtointeroperatewithanotherimplementationwhich
doesincludetheoption,thoughperhapswithreducedfunctionality.Inthesameveinanimplementation
whichdoesincludeaparticularoptionMUSTbepreparedtointeroperatewithanotherimplementation
whichdoesnotincludetheoption(except,ofcourse,forthefeaturetheoptionprovides.)
1.5 ApplicableDocuments
Whereappropriate,referencesareprovidedtoWMO,InternationalCivilAviationOrganization(ICAO),
AeronauticalRadioIncorporated(ARINC)orotherdocumentsthataresubjecttoissueandreviewbythe
respectiveorganizations.Norecommendationsorotherinformationinthisspecificationoverridesor
supersedestherequirementscontainedinreferenceddocuments,unlessspecifiedotherwise.
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1.6 AbbreviationsandAcronyms
ACARSAircraftCommunicationAddressingandReportingSystem
ACMSAircraftConditionMonitoringSystem
AMDAR
Aircraft
Meteorological
Data
Relay
ARINCAeronauticalRadio,Incorporated
ASDARAircrafttoSatelliteDataRelay
DASDataAcquisitionSystem
DEVGDerivedEquivalentVerticalGust
EDREddyDissipationRate
GNSSGlobal Navigation Satellite System
IATAInternationalAirTransportAssociation
ICAOInternationalCivilAviationOrganization
Q/CQualityControl
SATStaticAirTemperature
TATTotalAirTemperature
UTCUniversalTimeCoordinate
WMOWorldMeteorologicalOrganization
VHFVeryHighFrequency
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2 AMDARSystemOverview
2.1 AMDAR
system
TheAMDARsystemisdefinedbythecharacteristicthatitisameteorologicalobservingsystemthat
utilizesaircraftinnatesensorsandonboardavionicsandcommunicationssystemsinordertocollect
processandtransmitmeteorologicaldatathathasbeendefined,sampledandprocessedaccordingto
WMOmeteorologicalspecifications.
ThefullAMDARsystemcomprisestheendtoendsystemofprocessesandpractices,startingfrom
measurementbyaircraftsensorsrightthroughtothedeliveryofthedatatoDataUsers.Ontheaircraft,
AircraftDataComputersobtainprocessandformatdatafromonboardsensors,andtransmitdatato
groundviastandardaircraftcommunicationsystems.Onceontheground,thedataarerelayedtothe
NationalMeteorologicalServices(NMS)andotherauthorizedusersasshowninFigure1.Dataare
receivedatthedataprocessingcentersoftheNMSwheretheyaredecodedandundergobasicquality
controlchecksbeforebeingreformatted fordistributiontoDataUsersbothinternaltotheNMSand
externallytootherNMSsviatheWMOGlobalTelecommunicationSystem(GTS).
Figure1:AMDARDataFlow
Thisdocumentisconcernedonlywiththespecificationoffunctionalrequirementsfortheairborneor
onboardsoftwarecomponentoftheAMDARsystem,theAMDAROnboardSoftware.
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2.2 AMDAROnboardProcess
ThepurposeoftheairbornepartoftheAMDARProcess,henceforthreferredtoastheAOP,istocollect,
processandtransmitmeteorologicaldatafromsensorsonboardtheaircraft.Theprimaryfunctionsof
theAOPare:
Interfacetoandacceptinputdatafromavarietyofaircraftinnateavionicsequipment;
Performhighlevelqualitychecksontheinputdata;
Performcalculationsupontheinputdatatoderiverequiredmeteorologicalvariables;
Atsetintervals,processcollecteddataintostandardoutputmessagesfortransmissionto
groundstations;and,
Acceptandprocessinputs,allowinguserstoaltertheAOSbehavior.
To meet these primary functional requirements, AMDAR relies on the availability of onboard data
acquisitionsystemsthatarecapableofbeingprogrammedtoperformtherequiredfunctions.Therefore,
the firstandmost fundamental requirementof theAMDAROnboardSystem is that theaircraftmusthaveaDataAcquisition System (DAS) thatmustbeprogrammableand support interfacing toall the
requireddatainputsandtotheaircraftscommunicationssystem.
AnexampleofsuchanonboardsystemisillustratedinFigure2,whichshowsschematicallytheprincipal
datasourcesfeedingintoaDAS.Notethattheconfigurationsandavailabilityofsystemsvarieswidely
betweenaircraftmodelsandairlinefleets.
Data Aqcuisition
System
(programmable)
ACARS
Clock
1. Temperature
Wind Speed
Wind Direction
Altitude
2. Latitude
Longitude
3. Tail Number
Flight Number
4. Time (UTC)
5. Vertical Acceleration
6. AMDAR report
CENTRAL
MAINTENANCE
COMPUTER
1
3AIR DATA
COMPUTERS
6
2
INERTIAL
REFERENCE
UNITS
4 5
Flight Data
Recorder
Figure2:ExampleDataAcquisitionSystem
TypicalinputstotheDASare,forexample,PressureAltitudeorStaticAirPressure,WindSpeed/
Directionandothers.Theseinputparametersareprocessedbythesoftwareaccordingtopredefined
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samplingfrequenciesandtheresultingdatavariablesarestoredasameteorologicalobservation.
Then,dependingonthecommunicationssystemusedandrequirementsassociatedwithmessagecosts
andefficiency,datalatency,phaseofflightandotherparameters,whentherequirednumberof
observationshasbeenobtained,theyarewrittentoastandardizedmessagethatissubsequentlysentto
theground.
Theactualtriggeringoftheprogrammaticprocessesthatcreatetheseobservationsdependsonseveral
parametersthatareembeddedinthesoftware,manyofwhichareconfigurablethroughaninterfaceto
theAMDARsoftwareprogram.Theseparameterstellthesoftwarewhentoreportornottoreport.
Examplesofsuchparametersarephaseofflight,i.e.whethertheaircraftisascending,descendingorin
levelflight, pressurealtitude,geographicalpositionoftheaircraft,i.e.observationsaremadeonly
withinoroutsideofpredefinedgeographicallocations,andtimeofday,i.e.reportingisonlydonewithin
adefinedtimeframe.Bymakingtheseparametersconfigurable,theobservingandreportingregimefor
AMDARisabletobemodifiedaccordingtochangingmeteorological,programmaticoreconomic
requirements.
Additionally,bytakingadvantageoftwowayaircrafttogroundcommunicationsthatareoften
availablewithmodernaircraftavionicsandcommunicationssystems,itispossibletofacilitate
modificationoftheseprogramparametersviacommandsembeddedwithinuplink messages,whichare
usuallycompiledandsentbyautomated,groundbasedcontrolsystemsinnearrealtime.Thisprocessis
knownasAMDARdataoptimization.AMDARoptimizationsystemsallowNMSandairlinestomanage
datavolumesandeliminateredundantobservationsandmessagesthroughrealtimeAMDARsoftware
modificationeitherpriortoorduringaircraftflightandonaflightbyflightbasis.
TheendresultoftheAMDARonboardsystemistheproductionoftheAMDARmessagescontainingthe
meteorologicalobservations.Thesemessagesaretransmittedtothegroundbysuitabledatalink
communicationsystemsandrelayedbyaviationDataServiceProviderstotheNMS. Thecontentsofthe
messagesareprocessedandthedataareingestedintometeorologicaldatabasesandapplications.
2.3 OtherSpecifications
Therearemanypossibleformatspecificationsformeteorologicalmessagesfromaircraft. Inorderto
avoidtheproliferationofdataformatsandreducetheoverheadsandcomplexityforcomplianceby
groundprocessingsystems,thisdocumentprovidesafunctionalrequirementsspecificationthatwillbe
knownasAMDAROnboardSoftwareFunctionalRequirementsSpecification(AOSFRS)Version1.0.This
specificationisbasedontheASDARSpecification2,theEAMDARAAAVersion2.0Specification(AAA
V2)3andtheAMDARAAAVersion3.0specification(AAAV3)4. Allinformationinthisdocument
supersedesthepreviouslymentioneddocuments.Someinformationinthisdocumentisderivedfrom
2SoftwareRequirementsSpecificationfortheASDARProject,Issue3,MatraMarconiSpaceUKLimited,October
1994(reference116300016444).
3EUMETNETAMDARAAAAMDARSoftwareDevelopmentsTechnicalSpecification,Version2,1August2000.
4PROGRAMOPERATIONSANDSTANDARDSOBSERVATIONSSPECIFICATION20061,AMDARAAAVersion3.0
SoftwareRequirementsSpecification,23November2006
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ARINCspecification620(meteorologicalreportversion1thru5).TheARINCspecificationhoweverisnot
supersededbythisdocument.
Sincemostmeteorologicalmessagesshareacommonapproachtoprocessing,triggeringand
transmittingdataitispossibletousethisspecificationinconjunctionwithotherspecifications.In
particular,theARINC620MeteorologicalReportspecificationisarecognizedstandardforAMDARanditisthereforefeasibleandacceptabletospecifythatparticulardownlinkformatstandardasanalternative
tothosespecifiedwithinthisdocument.
Toallowtheusertochoosebetweenoptionalformats,thisspecificationshallrefertotheARINC620
(latestversion)specificationwhereappropriate.
2.4 FurtherReading
AdetaileddescriptionoftheAMDARsystemisgivenintheAircraftMeteorologicalDataRelay(AMDAR)
ReferenceManual(WMONo958)availablefromtheWorldMeteorologicalOrganization,Geneva,
Switzerland:
http://www.wmo.int/amdar/Publications/AMDAR_Reference_Manual_2003.pdf
andintheWMOGUIDETOMETEOROLOGICALINSTRUMENTSANDMETHODSOFOBSERVATION,Part2,
Chapter3,AircraftObservations:
http://www.wmo.int/pages/prog/www/IMOP/CIMOGuide.html
http://www.wmo.int/amdar/Publications/AMDAR_Reference_Manual_2003.pdfhttp://www.wmo.int/amdar/Publications/AMDAR_Reference_Manual_2003.pdfhttp://www.wmo.int/pages/prog/www/IMOP/CIMO-Guide.htmlhttp://www.wmo.int/pages/prog/www/IMOP/CIMO-Guide.htmlhttp://www.wmo.int/pages/prog/www/IMOP/CIMO-Guide.htmlhttp://www.wmo.int/pages/prog/www/IMOP/CIMO-Guide.htmlhttp://www.wmo.int/pages/prog/www/IMOP/CIMO-Guide.htmlhttp://www.wmo.int/amdar/Publications/AMDAR_Reference_Manual_2003.pdf -
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3 AMDAROnboardSoftwareRequirementsAsdescribedinchapter2,theprimaryfunctionsoftheAMDAROnboardProcessare:
Acceptinputdatafromavarietyoftheaircraftinnateavionicsequipment.
Performhighlevelqualitychecksontheinputdata
Performcalculationsupontheinputdatatoderiverequiredmeteorologicalparameters
Atsetintervals,processcollecteddataintostandardoutputmessagesfortransmissionto
groundstationsand
Acceptinputs,allowinguserstoaltertheAMDAROnboardSoftwarebehavior.
Figure3showsahighlevelschematicoftheAMDARonboardprocess. Thischapteraimstotranslatethe
functionsinthisschematicintofunctionalrequirementsfortheAMDARonboardsoftware.
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Data Handling
AMDARMessage
Compiler
AMDAR MessageConfiguration
Message
SoftwareConfiguration
ConfigurationModule
ConfigurationMessage
Compiler
Observations
Observation
Scheduler
Aircraft Avionics Data In
AMDAR Inf ormation Out AMDAR Messages, AMDAR Configurati on
Message
Configuration
Setting
s(uplink/flightdeck/codechanges)
Data Aqcuisition
AMDAR ONBOARD SOFTWARE
Figure3:AMDAROnboardProcess
3.1 DataAcquisition
Thedataacquisitionsystemshallprovideadatainterfacetothehighestqualitydatasourcesavailable
fromtheaircraft.Incasethedirectsourceisnotavailabletotheacquisitionsystemitisacceptableto
useanindirectsource,aslongasthequalityofthedataismaintained(e.g.thelatitudecomesfromthe
inertialreferencesystembutthissourceisnotconnecteddirectly totheAOS.Latitudeishowever
transmittedtotheFMCandthissourceisavailabletotheAOS.Aslongasdataqualityismaintainedthe
latitudecanbeobtainedfromtheFMCinsteadofdirectlyfromtheIRS)
Thetablesbelowprovidetheinputsignalsthatneedtobeacquired.Distinctionismadebetweensignals
thatshallbeacquired(Table1
Table1:InputSignals Required
),shouldbeacquired(Table2)andsignalsthatareoptional(Table3).
DESCRIPTION UNIT RANGE ACQRATE
PREFERRED MAX
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AIRCRAFTID INT N/A N/A N/A
AIR/GROUNDSWITCHORWEIGHTONWHEELS DISCRETE N/A 1HZ 1HZ
COMPUTEDAIRSPEED KTS 0TO800KNOTS 1HZ 2HZ
DATEDAY DD 031 1HZ 4HZ
GMTHOURS HH 0023 1HZ 2HZ
GMTMINUTES MM 0059 1HZ 2HZ
GMTSECONDS SS 0059 1HZ 2HZ
LATITUDE DEGR 90STO90N 1HZ 4HZ
LONGITUDE DEGR 180ETO180W 1HZ 4HZ
PRESSUREALTITUDEINICAOSTANDARDATMOSPHERE1)
BAROMETRICALTITDUEINQNHADJUSTEDATMOSPHERE1)
FT1,000TO50,000
FEET1HZ 2HZ
STATICAIRTEMPERATURE DEGR.C 99CTO+99C 1HZ 2HZ
STATICPRESSURE2) HPA(=MB) 1HZ 1HZ
WINDDIRECTIONTRUE DEGR 0TO360 1HZ 2HZ
WINDSPEED KTS 0TO800KNOTS 1HZ 2HZ
Note1: PressureAltitudeinICAOStandardAtmosphere=PALT
BarometricAltitudeinQNHadjustedatmosphere=BALT
IfbothPALTandBALTareavailable,PALTshouldbeused.
Note2: Ifstaticpressureisnotavailablefromtheaircraftsystemsitcanbecalculatedfrompressurealtitude
ForPALTequaltoorlessthan36089ft.,staticpressure(SP)isrelatedtoPALT(ft)bythefollowingexpression:
SP(hPa)=1013.25[1106x6.8756(PALT)]
5.2559
IfPALTisgreaterthan36089ft,staticpressureisgivenby:SP(hPa)=226.32exp((PALT36089)/20805)
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Table2:InputSignals Recommended
DESCRIPTION UNIT RANGE ACQRATE
PREFERRED MAX
DEPARTURESTATION CHAR N/A N/A N/A
DESTINATIONSTATION CHAR N/A N/A N/A
VERTICALSPEED3)
FT/MIN 2000TO2000 1HZ 1HZ
GROSSWEIGHT KG N/A 1HZ 16HZ
VERTICALACCELERATION G 3GTO+6G 8HZ 4HZ
ROLLANGLE DEGR 180TO180 1HZ 1HZ
PITCHANGLE DEGR 90TO90 1HZ 1HZ
Note3: Verticalspeedisusedinphaseofflightdetermination.Verticalspeedmaybederivedfromaltituderateofchange
Table
3:
Input
Signals
Optional
DESCRIPTION UNIT RANGE ACQRATE
PREFERRED MAX
WATERVAPORDATA/RELATIVEHUMIDITY NOTE4 1HZ 4HZ
ICINGDATA DISCRETE N/A 1HZ 4HZ
FLAPS DEGR 1HZ 4HZ
GEARDOWN/UP DISCRETE N/A 1HZ 2HZ
GNSSALTITUDE FT 1,000TO50,000FEET 1HZ 1HZ
GROUNDSPEED KTS 0TO800KNOTS 1HZ 2HZ
TRUETRACK DEGR 1HZ 2HZ
TRUEHEADING DEGR 0TO360 1HZ 2HZTRUEAIRSPEED KTS 0TO800KNOTS 1HZ 2HZ
Note4: WaterVapor/Humidityismeasuredandreportedeitherasmixingratioorrelativehumidity,dependingonthetypeof
sensoremployed.Themassmixingratiovalueistobereportedasnnnnn=n1n2n3n4n5whichimpliesamassmixingratio
valueof(n1n2n3n4)x10(3n5)
kg/kg;e.g.,ifnnnnn=12345,thenthemassmixingrationisgivenby1234x10(3 5)
=1234x108
kg/kg.
RelativeHumidityisreportedasnnnnnwheretherangeofnnnnnisbetween00000and10000inhundredsofpercent.
3.2 DataHandling
3.2.1 Dataacquisitionrate
Input
data
can
be
acquired
at
different
acquisition
rates.
For
instance,
data
can
be
acquired
8
times
per
secondbutitisalsopossibletohaveparametersacquiredonceeverytwoorfourseconds.Following
rulesdescribehowtohandleacquisitionrates.
1. Forinputdataacquiredoncepersecond,nospecialruleapplies
2. Forinputdataacquiredmorethanoncepersecond,thelastvalidsamplewithinthatsecond
shallbeused
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3. Forinputdataacquiredlessthanoncepersecond,thelastvalidsampleshallbeused.
3.2.2 DataValidation
InputDatashouldonlybeusedwhen:
1. Itisvalidatedusingapplicableavionicsvalidationstandardsand,
2. ItpassestheoutofRangecheck.Inputdatavaluesshouldbecheckedagainsttherangegivenin
Table1,Table2andTable3.Whentheinputdatavaluefallsoutsidethisrangeitisconsidered
invalid.
Datathatisinvalidshallnotbeusedinanycalculation.Observationsshallcontinuebutinvaliddatashall
eithernotreported,orbemaskedasspecified,usuallywithasolidi(/).
3.2.3 DataSmoothing
WhilepreviousspecificationsfortheAOShaveincorporatedalgorithmsforsmoothingoraveragingdata
parameters,thispracticeisnotrecommendedwithoutclearscientificallybasedjustification.Smoothing
oraveragingshouldnotbeimplemented.
3.2.4 DerivedParameters
3.2.4.1PhaseofFlight
AMDARobservationintervalsshouldbelinkedtoaircraftflightphase.Thefollowingphasesofflight
conditionsshouldberecognized:
a) Ground
b) Ascent
c) Level
flight
(or
Cruise
or
En
route)
d) Descent
AnassessmentofthePhaseofFlightshouldbemadeatregularonesecondintervals.Theaircraftwillbe
consideredtooccupyoneofthephasesofflightatanytime,buttransitionfromonephasetoanother
doesnotnecessarilyfollowtheorderlistedabove,exceptthatPhaseAscentshallalwaysfollowPhase
or60se inimum.Groundf condsm
3.2.4.1.1 Ground
Theaircraftisconsideredonthegroundwhenitisnotinoneofthereportingflightmodes(ascent,en
routeordescent).Theaircraftisingroundphasewhen:
1. ComputedAirspeedisequaltoorlessthan100knotsorComputedAirspeeddataisinvalid,and
2. Air/groundswitchindicatesgroundorweightonwheelsistrue
Duringthisphasethesoftwareprocessesdatabutnoobservationnoraretransmissionsmade
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3.2.4.1.2 Ascent
Theaircraftisinascentwhen:
1. ComputedAirspeed>100ktsand
2. AltitudeRate>+200feet/minand
3. a.Pressurebasedscheme:PressureAltitudeTopofClimb(seeTable7)or
.Time eme:Flighttimesincetakeoff>Ascenttotalduration(seeb basedsch
3.2.4.1.4 Descent
)
Theaircraftisindescentwhen:
1. ComputedAirspeed>100ktsand
2. AltitudeRate
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Theflagisusedinoneoftwomodes:
Mode1:eitherasaqualityindicatorforwindspeedanddirectionbasedontheaircraftrollangle(RA)
andpitchangle(PA)(Mode1),or,
Mode2: toprovideanindicationofwhichrangebintheaircraftrollanglevaluelieswithin.
InMode1,theRollAngleFlagwilltakethevalueB,G,H,WorU,withthecorrespondingmeaning
providedinthetablebelow.
InMode2,theRollAngleFlagwilltakeeitherthevalueH,WorUwiththesamemeaningforMode1,or
anintegervaluefrom0to9.
ThevaluesWandUareusedwithinanEnrouteWeathermessageonlytoindicatethattheWindSpeed
constitutesaMaximumWindReportasperthecriteriadefinedinParagraph3.4.1.1.
Table4:RollAngleFlagvalues
ROLLANGLEFLAGVALUE MEANING MODE
B |RA| 5OR(|RA|3AND|PA| 3) 1
G |RA|
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3.2.4.5AircraftConfigurationIndicator
Aderivedparameterrepresentingtheaircraftconfigurationstatusmaybeaddedtothemeteorological
observationdata.Whenused,theparametershallbeassignedavalueaccordingtotheconfiguration
statusoftheaircraftasinthefollowingtable:
Table5:AircraftConfigurationIndicatorValues
VALUE MEANING
0 CONFIGURATIONUNDEFINED/NOTREPORTABLE
1 CLEANCONFIGURATION,GEARRETRACTED
2 FIRSTPOSITIONOFFLAPSEXTENSION,GEARRETRACTED
3 SECONDPOSITIONOFFLAPSEXTENSION,GEARRETRACTED
4 THIRDPOSITIONOFFLAPSEXTENSION,GEARRETRACTED
5TO7 RESERVED
8 ONLYLANDINGGEARDOWNANDINPLACE
9 FIRSTPOSITIONOFFLAPSEXTENSION+LANDINGGEARDOWNANDINPLACE
10 SECONDPOSITIONOFFLAPSEXTENSION+LANDINGGEARDOWNANDINPLACE
11 THIRDPOSITIONOFFLAPSEXTENSION+LANDINGGEARDOWNANDINPLACE
12TO14 RESERVED
15 WEIGHTONWHEELS=TRUE
3.3 AMDARObservations
AcrucialfunctionoftheAMDARsoftwareistotriggerandstoreobservations.Anobservationisasingle
setof(calculated)parametervaluesatapointinspaceandtime.
Observationsaremadeduringfollowingphasesofflightonly:
Ascent
Enroute(orCruise) Descent
Observationsshallbemadeeither:
1) Whenapresetstaticpressurelevelisreached(Pressurebasedscheme,default)
2) Whenapresettimeperiodhaselapsed(TimeBasedscheme)
Thesoftwareshallbecapableofswitchingbetweeneitherschemebutonlyoneschemeshallbeactive
atanygiventime.
Observationsshallbestoredinadedicatedareaofmemoryuntilrequired.
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3.4 ObservationFrequency
Thefrequenciesatwhichmeteorologicalobservationsaremadedependonthephaseofflightthe
aircraftisin.Eachobservationhasthesameorderingofmeteorologicalinformationbutthetriggering
frequencycanvarywithphase.
ThefigurebelowillustrateshowAMDARshoulddifferentiatebetweenthevariousflightphases.
Ascent
Part 1
Ascent
Part 2En-route
Descent
Part1
Descent
Part 2
Top of Climb
100hPa
Top of Descent
Figure4:AMDARflightphases
Thetablebelowdescribestheobservingfrequencyforthevariousflightphases.Paragraphsfollowing
providedetailedinformationontheobservingfrequency
Table6:AMDARobservingIntervalbyflightphase
Table6
PRESSUREBASEDSCHEME TIMEBASEDSCHEME
ASCENTPART1 5OR10HPAINTERVALSFORFIRST100HPA 3TO20SECSINTERVALS(DEFAULT6)FOR30TO200SECS
(DEFAULT90)
ASCENTPART2 25OR50HPAINTERVALSABOVEFIRST100HPA 20TO60SECSINTERVALS(DEFAULT20)FOR490TO
1050SECS(DEFAULT510)
EN
ROUTE: 1TO60MINUTEINTERVALS(DEFAULT7)
DESCENTPART1 25OR50HPAINTERVALSFROMTODTOLAST
100HPA
20TO300SECSINTERVALS(DEFAULT40)FROMTOPOF
DESCENTTOTOUCHDOWN.
DESCENTPART2 5OR10HPAINTERVALSFORLAST100HPA
Theparagraphsbelowprovidedetailedinformationonthecontentof .
3.4.1 En-routeObservations
TheEnrouteobservationfrequencyisgenerictoboththepressureandtimebasedscheme.
Observationsshallbetriggeredatsettimeintervalsonly. Enroutedatameasurementsshouldbeginat
theconclusionofAscentandterminatewhenDescentobservationmeasurementsbegin.
FortimeintervalvaluesseeTable8.
3.4.1.1MaximumWindObservation
Thisfacilityisrequiredtoaidinlocatingjetstreamcoresandisappliedinenrouteflightphaseonly.The
highestwindspeedmeasuredbetweenasequentialpairofroutineobservationsislabeledmaximum
wind.Maximumwindisderivedaccordingtothefollowingcriteria:
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1. Observationsofwindspeedmaximawillonlybereportedwhentheambientpressureis lower
than600hPa,and
2. Theaircraftisinenroute,and
3. Thewindspeedexceeds60knotsabsolute,and
4. The wind speed exceeds by 10 knots or more the value observed at the previous routine
observation,and
5. Thewind speedexceedsby10 knots ormore the valueobservedat the subsequent routine
observation.
TheMaximumWindoption,providesanadditionalobservationthatistakenatthetimeofoccurrence
ofthepeakwindmeasurement,usingthemaximumwindindicator(seeTable4)
3.4.2 PressureBasedScheme
3.4.2.1RoutineObservations
Routineobservationwillensuredataisstillcollectedatregulartimeintervalsinthecasewherethe
aircraftlevelsoffduringascentand/ordescentandstaticpressuretriggeringcannotbeusedsincethe
staticpressuredoesnotchangeduringlevelflight.Itwillalsoensurethatobservationsaretakenifthe
aircraftdoesnotreachthesetaltitudefortopofclimb.
Routineobservationsshallbemadeatsettimeintervalsduringflightphaseascentanddescent. The
intervaltimerresetsandcommencesfollowingeachobservation.Ifnopressurelevelchangeis
encounteredduringthepresettimeinterval,anobservationistriggeredandthetimerisreset.Thetime
intervalisthesameastheenrouteobservationtimeinterval(seeparagraph3.4.1)
3.4.2.2
Ascent
DuringPhaseofFlightAscent,observationsshallbemadeatdefinedAmbientStaticPressurelevels
whichwillbeknownas"AscentTargetPressures".ThesewillbereferencedtotheAmbientPressureat
takeoff.
3.4.2.2.1 Initial Observation
Meteoro dalogical (takeoff).tameasuredatthetimeoftheOFFevent
3.4.2.2.2 Ambient Static Pressure at TakeOff
Atthetimeoftakeoff,theAmbientStaticPressureshallbedeterminedbynotingtheaveragevalueofp
takenbetweenthesecondsuccessivemeasurementoftheComputedAirspeedthatexceeds60knots
andthesecondsuccessivemeasurementoftheComputedAirspeedthatexceeds90knots.TheAmbient
StaticPressureattake offwillbestored.
IftheComputedAirspeedfallsbackbelow60knotsbeforeAscentisentered,butafteranAmbientStatic
Pressureattakeoffvalueisstored,thenthevaluestoredshallbeoverwrittenwhentheComputed
Airspeednextincreasesfrom60through90knots.
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3.4.2.2.3 Ascent Part 1
ObservationsshallbemadewhentheAmbientStaticPressurefirstfallsbelowtheAscentTarget
Pressure.ThefirstAscentTargetPressureshallbethenearestmultipleof10hPa(modifiableto5hPa)
belowtheAmbientStaticPressureattakeoff.Thenextnine(modifiableto19if5hPaisused)Ascent
TargetPressuresshallfollowat10hPa(modifiableto5hPa)intervalsdecrementingfromthefirstAscent
essureTargetPr level.
3.4.2.2.4 Ascent Part 2
TheeleventhAscentTargetPressureshallbethenearestmultipleof50hPa(modifiableto25hPa)below
thetenthAscentTargetPressure.ThetwelfthandsubsequentAscentTargetPressuresshallfollowat50
hPa(modifiableto25hPa)intervalsdecrementingfromtheeleventhAscentTargetPressure.
Observationswillcontinueat50hPa(modifiableto25hPa)intervalsthroughouttheremainderofthe
AscentPhase.
ThecompleteAscentdataprofilewillthusconsistoftenobservationsat10hPa(ortwentyat5hPa)
intervalsoverthefirst100hPa,andObservationsat50hPa(or25hPa)intervalsthereafteruntilthe
Ascentiscomplete.
3.4.2.3Descent
DuringPhaseofFlightDescent,ObservationsshallbemadeatdefinedAmbientStaticPressurelevels,
whichwillbeknownas"DescentTargetPressures".
ThefirstDescentTargetPressureshallbethefirstmultipleof50hPa(modifiableto25hPa)abovethe
pressurerecordedwhentheDescentphasewasestablished.SubsequentDescentTargetPressuresshall
beat50hPa(modifiableto25hPa)intervals.ObservationsshallbemadewhentheAmbientStatic
PressurefirstrisesabovetheDescentTargetPressure.
Atandabove700hPathesoftwareshall,inadditiontothecontinuedformationofObservationsat50
hPaintervals,formObservationsat10hPaintervalsincrementingfrom700hPa.Onlythetenmost
recentObservationsat10hPaintervalsareretained.Thisadditionalsamplingshallcontinueuntilthe
Descentiscompleted.Intheeventoftheaircraftlandingbeforeacompletesetof50hPa(modifiableto
25hPa)observationshavebeenmadethemessagewillbepaddedoutwiththe/characterfollowedby
anewmessagewhichcontainsthetenObservationsmadebeforetouchdown.Thecompletesetof
DescentObservationsisthusaseriesofobservationsat50hPaintervals,augmentedbyadetailed
verticalsurveyofthelast100hPain10hPaincrements,whichshallnotincluderepeatsofobservations
at50hPaintervals.
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3.4.3 TimeBasedScheme
3.4.3.1A
3
scent
.4.3.1.1 Initial ObservationAninitial ationis
3.4.3.1.2 Part 1
observ triggeredattheOFFevent.
FollowingtheInitialobservation,observationsareaccumulatedatsettimeintervalsuntilthepart#1
limitis d,countedfromtheOFFevent.Forintervalanddurationvaluesseeduration reache
3.4.3.1.3 Part 2
Table7
Table7
ObservationsareaccumulatedfromtheexpirationofthePart#1dataacquisitionperiod.Part#2data
observationsaretakenatsettimeintervalsuntiltheAscenttotaldurationlimitisreached,countedfrom
theOFFevent.Forintervalanddurationvaluessee
3.4.3.2Descent
DescentdatameasurementsbeginatTopofDescentandareaccumulatedatasettimeinterval.Topof
Descentismodifiable.
ForTopofDescentandintervalvaluesseeTable9.
3.5 MessageCompilation
3.5.1 Content
Observationsarecollectedandstoredduringflight.Whenapresetnumberofobservationsarestored,
amessageshallbeformedcontainingtheseobservations.Afteramessageistransmitted,the
observationsshallbediscarded.Themessageshallhaveatleastthefollowinginformation:
IdentificationasAMDARdata
Softwareversionindicatori.e.whatspecificationitconformsto
Reportingscheme(timebasedorpressurebased)
Observationdata
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3.5.2 Format
Themessageformatdependsonthestandardadopted.ForAOSFRS(thisdocument)seeAppendixA.
3.5.3 Transmission
Regardlessoftheformat,messagesshallbesendtothegroundassoonastheyarecompleteviathe
bestmeanspossible.
Pendingmessagesshallbesendeventhoughthepresetnumberofobservationshasnotbeenreached
insituationsoutlinedbelow:
1. Flightphasetransitions
Forexample;theaircrafttransitionsfromflightphaseascenttoflightphaseenroute,thepre
setnumberofobservationsistenbutonlyfiveobservationsarestored.Inthiscase,amessage
shallbesendwithonlyfiveobservations.
2. Reportingturnedoffbysoftwarecontrol
Forexample;reportingduringdescentisturnedoninitially.Duringdescent,reportingis
switchedoffbyuplinkcommand.Atthattimeonlysevenobservationswerestored.Inthiscase,
amessageshallbesendwithonlysevenobservations.Moreinformationonsoftware
configurationcontrolcanbefoundinparagraph3.6.
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3.6 SoftwareConfigurationControl
Itshallbepossibletoconfigurethesoftwaretoallowreportingbehaviortobealtered.
Changesinconfigurationareestablishedbyanycombinationofthefollowingmethods(inorderof
preference):
1. ACARSuplinkcommands
2. Manualentrythroughflightdeckinterfacedisplays
3. Codechanges
Changestotheconfigurationbyoneofthemethodsdescribedaboveareconsideredpermanentuntil
changedagain.Ifforwhateverreasontheconfigurationsettingsarelost,thesettingsshallrevertto
default.
3.6.1 ObservationFrequency
Control
FollowingtablesdescribetherequiredobservationfrequencycontrolparametersforAscent,Enroute
andDescent.
Table7:Ascentobservationcontrolparameters
CHARACTERS DATA DESCRIPTION REMARKS
1 0OR1 PRESSUREBASEDSCHEME(0)ORTIMEBASEDSCHEME
(1)
DEFAULT =0
2 SS ASCENTPART1TIMEINTERVAL(SECONDS) TIMEBASEDSCHEME
DEFAULT=06
RANGE=0320
3 SSS ASCENTPART1DURATION(SECONDS) TIMEBASEDSCHEMEDEFAULT=090
RANGE=030200
2 SS ASCENTPART2TIMEINTERVAL(SECONDS) TIMEBASEDSCHEME
DEFAULT=20
RANGE=2060
3 SSS ASCENTTOTALDURATION(SECONDSX10) TIMEBASEDSCHEME
DEFAULT =051
RANGE=051111
2 NN PART1PRESSUREINTERVAL(HPA) PRESSUREBASEDSCHEME
VALUE=5OR10
DEFAULT=10
2 NN NUMBEROFOBSERVATIONSMADEDURINGASCENTPART1.
PRESSUREBASEDSCHEMEVALUE=10OR20
DEFAULT=10
NOTE:PART1PRESSUREINTERVALXPART
1NUMBEROFOBSERVATIONSMUSTBE100
2 NN PART2PRESSUREINTERVAL(HPA) PRESSUREBASEDSCHEME
VALUE=25OR50
DEFAULT=50
3 NNN TOPOFCLIMB(X100FT) DEFAULT=200
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RANGE=1503501)
1 0OR1 ROUTINEOBSERVATIONSENABLED(1)ORDISABLED(0) DEFAULT=1
Note1:DefaultsettingsfortheTopOfClimbmustbechosentomatchoperationalprofilesoftheaircrafttype,i.e.
theymustbesetlowerthanthecommoncruisealtitudefortheaircrafttypethesoftwarewillbeinstalledon.
Table8:
En
route
observation
control
parameters
CHARACTERS DATA DESCRIPTION REMARKS
2 MM OBSERVATIONINTERVAL(MINUTES) DEFAULT=7
RANGE=160
1 0OR1 ENABLE(1)ORDISABLE(0)MAXIMUMWIND
REPORTING
DEFAULT=1
Table9:Descentobservationcontrolparameters
CHARACTERS DATA DESCRIPTION REMARKS
1 0OR1 PRESSUREBASEDSCHEME(0)ORTIMEBASEDSCHEME
(1)
0=DEFAULT
3 SSS DESCENTTIMEINTERVAL(SECONDS) TIMEBASEDSCHEMEDEFAULT=040
RANGE=010300
2 NN DESCENTPRESSUREINTERVAL(HPA) PRESSUREBASEDSCHEME
VALUE=25OR50
DEFAULT=50
3 NNN TOPOFDESCENT(X100FT) DEFAULT=200
RANGE=150350
1 0OR1 ROUTINEOBSERVATIONSENABLED(1)ORDISABLED(0) DEFAULT=1
3.6.2 ReportingControl
3.6.2.1
Reporting
on/off
Itshallbepossibletoturnreportingonoroffcompletelyorbyflightphase,inaccordancewiththetable
below:
Table10:AMDARswitch
CHARACTERS DATA DESCRIPTION REMARKS
1 N REPORTACTIVATIONFLAG 0=REPORTINGOFF(DEFAULT)
1=DESCENTPHASEONLYACTIVE
2=ENROUTEPHASEONLYACTIVE
3=ENROUTE&DESCENTPHASESACTIVE
4=ASCENTPHASEONLYACTIVE
5=ASCENT&DESCENTPHASESACTIVE
6=ASCENT&ENROUTEPHASESACTIVE
7=ALLFLIGHTPHASESON
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3.6.2.2GeographicalControlboxes
Itshallbepossibletoconfigureaminimumof10geographicalboxesinwhichreportingisenabledor
disabled.Outsidetheseboxesreportingisdisableddependingontheairportlimitation(see
paragraph0).
Aboxisdefinedbysettingtwolateralandtwolongitudinalboundariesindegrees.Whendefiningthe
boundaries,SOUTHandWESTarenegativei.e.20Sis20and40Wis040
TheareawillalwaysbedefinedasthatbetweenLAT1toLAT2inasoutherlydirection,andLON1to
LON2inaneasterlydirection(20N80S,120W50Eforexample).
Figure5:GEOboxdescription
Theorderofpriorityfortheseboxesshouldbefrom10(ormoreifimplemented)to1,thusallowinga
largeareatobeenabledforreportingusingbox1andasmallerregiontobedisabledwithinthisbox,
usingbox2forexample. Defaultsettingsareasfollows:
Table11:Geographicalcontrolboxdefaultsettings
BOX LAT1 LAT2 LON1 LON2 STATUS
1 90 90 180 180 DISABLEREPORTING
2 90 90 180 180 DISABLEREPORTING
3 90 90 180 180 DISABLEREPORTING
4 90 90 180 180 DISABLEREPORTING
5 90 90 180 180 DISABLEREPORTING
6 90 90 180 180 DISABLEREPORTING
7 90 90 180 180 DISABLEREPORTING
8 90 90 180 180 DISABLEREPORTING
9 90 90 180 180 DISABLEREPORTING10 90 90 180 180 ENABLEREPORTING
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3.6.2.3Airportspecificreporting
Itshallbepossibletoconfigureaminimumof20airportsaroundwhichreportingforascent,descentor
both,canbeenabledordisabled.Thesettingsappliedtothesespecificlocationsshalltakepriorityover
thegeographicallimitingfunction.
EachairportshallbedescribedbyitsfourletterICAOairportdesignator.Aflagisusedtocontrol
whetherobservingduringascent,descentorbothisactivatedordeactivatedforthislocation.Following
tableshowstheparameterconfigurationforthefirstairport.Thisistoberepeated19times.
Table12:Airportcontrolparameters
CHARACTERS DATA DESCRIPTION REMARKS
4 IAIAIAIA ICAOAIRPORTDESIGNATOR 0000 =DEFAULT
1 FA AIRPORTACTIVATIONFLAG 0=ASCENTON/DESCENTON(DEFAULT)
1=ASCENTON/DESCENTOFF
2=ASCENTOFF/DESCENTON3=ASCENTOFF/DESCENTOFF
3.6.2.4TimeLimiting
Itshallbepossibletoconfigureasingletimewindowduringwhichreportingisinhibited.
Table13:Timelimitcontrolparameters
CHARACTERS DATA DESCRIPTION REMARKS
4 H1H1H2H2 DISABLEOBSERVATIONSBETWEENSELECTED
HOURS(0023)UTC,EVERYDAY
H1H1=STARTOFINHIBITPERIOD
H2H2=ENDOFINHIBITPERIOD
DEFAULT=0000Thedefaultvalueisinterpretedasnointervalselectedandreportthoughall24hourperiods.Theinhibit
periodstartsatthefirstdesignatedhourinthedayandendswhenthenextdesignatedhourisreached
thesameornextday.Thus2301meansinhibitbetween2300hoursand0100hoursthenextday,every
day.(twohoursspanningmidnightUTC).
3.6.3 ConfigurationMessage
Thesoftwareshallprovideforamessagethatliststhecurrentsettingsforallofthecontrolparameters
mentionedinpreviousparagraph.
Themessagecanberequestedviaeither(inorderofpreference)
1. Anuplinkcommand.
2. Manualrequestthroughflightdeckinterfacedisplays
ForcontentsandformatoftheconfigurationmessageseeAppendixB
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3.6.4 AMDAROptimizationMessage
AnAMDARoptimizationmessagemaybesenttotheNMSand/orairlinepriortodepartureofevery
flight.ThismessageallowstheNMSand/orairlinetoalterthesoftwareconfigurationpriortoflightand
therebymanagedatavolumesandeliminateredundantobservationsandmessages.
Forexample,anascentprofileisrequiredforanairportonlyonceperhour.Butifduringthathourmore
thenoneAMDARequippedaircrafttakesoff,thesystemisfilledwithdatathatisnotrequired.Inorder
topreventmultipleaircraftsendingAMDARmessages,agroundbasedsystemdetermineswhataircraft
toswitchoffbyusingtheinformationintheoptimizationmessage.
TheoptimizationmessagemaybeastandardOOOImessagebutshouldatleastcontain:
AircraftIndicator
TimeOut(leavinggateorparkingposition)
Departure/ArrivalStation
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AppendixA AOSFRSmessageformatversion04
A.1 Introduction
ThisappendixspecifiestheAOSFRSmessageformat.TheAOSFRSmessageformatprovidesabasicmeteorologicalmessagewithonlytheminimumamountofinformationthatwillstillrenderamessage
usefulasameteorologicalmessage.Atthesametimeitallowsmaximumflexibilitytoaddinformation
thatenhancesthebasicreport,ifthisinformationisavailable.
Reasonforthisapproachistoallowtheformattobeusedonawidevarietyofaircraft/airlineswhere
somemayonlyhavethebasicinformationavailable,andothersmaybeabletoprovidealotmore
information.
Thedatathatissendtothegroundissetupintwosections,thefirstaheadersectionwithinformation
suchastheAOSFRSmessageversionandtheaircraftidentifier,thesecondpartconsistsof10
observationswiththerelevantparametervalues.Adetaileddescriptionisgivenbelow.
A.2 Header
Eachmessageshallhaveaheadercontainingtheinformationasdescribedinthetablebelow.
Table14:AOSFRSmessageheader
LINE
NUMBER
CHARACTER
NUMBER
#OFCHAR CONTENT FORMAT NOTES
1 13 3 AMDARMESSAGEVERSION A04
2 126 1TO26 OPTIONALPARAMETERINDICATION #ORATHRUZ SEEOPTIONAL
PARAMETERS
3 17 8 AMDARAIRCRAFTIDENTIFIER AAAAAAAA 1
3 8 1 NORMAL(N)ORCOMPRESSED(C) NORC 2
3 9 1 TIMEBASED(0)ORPRESSUREBASEDSCHEME
(1)
0OR1
3 10 1 ALTITUDEREFERENCE:PRESSUREALTITUDE
(P)ORBAROMETRICALTITUDE(B)
PORB 3
3 1114 4 DEPARTUREAIRPORT AAAA 4
3 1518 4 ARRIVALAIRPORT AAAA 4
Notes:
1. TheAMDARidentifierisassignedbytherequestingmetoffice.
2.
Normal means the data is not compressed. Compressed means the data is encoded using the
compressionschemedescribedinAppendixD.
3. PressureAltitudeinICAOStandardAtmosphere=PALT;
BarometricAltitudeinQNHadjustedatmosphere=BALT;
IfBALTisreported,conversiontothePressureAltitude(PALT)scalewillbenecessaryingroundprocessing
usingrunwayorareaQNHatthetimeoftheobservation.Thisisessentialbeforedatacanbeusedor
exchanged.IfbothPALTandBALTareavailable,PALTispreferred.
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4. DepartureandArrivalairportarerepresentedbytheirICAOcode.Reportingofthesefieldsisoptionalbut
ifavailable,stronglyrecommended.
A.3 Body
Theheadershallbefollowedby10meteorologicalobservations,eachobservationononeline.The
observationsshallcontaintheBasicObservationSequenceasdescribedin .Allparametersshallberightjustified.
Table15
Table15:AOSFRSBasicObservationSequenceformat
A.3.1 BasicObservationsequence
CHARACTER
NUMBER
#OF
CHAR
CONTENT FORMAT NOTES EXAMPLE
1 1 PHASEOFFLIGHTINDICATOR A 1 R
26 5 LATITUDEINMINUTES SNNNN SOUTHISNEGATIVE 2976
712 6 LONGITUDEINMINUTES SNNNNN WESTISNEGATIVE 6081
1319 7 DAY/TIME NNNNNNN 2 8796612023 4 ALTITUDEINTENSOFFEET NNNN 3899
2427 4 STATICAIRTEMPERATURETENTHSOFC SNNN 525
2830 3 WINDDIRECTION NNN 160
3133 3 WINDSPEED NNN 025
Notes:
1. PhaseofFlightisindicatedasfollows:
Ascent =A
Enroute=R
Descent=D
2. The
day/time
is
presented
as
seconds
into
the
month,
and
is
calculated
as
follows:
( ( DATEDD- 1) *86400) + ( GMTHH*3600) + ( GMTMM*60) + GMTSS
Example1:
AnobservationismadeonJuly1stat20:53:22UTC,thecorrespondingday/timewillbe
((11)*86400)+(20*3600)+(53*60)+22=75202secondsintothemonth
Example2:
AnobservationismadeonNovember11that04:21:01UTC,thecorrespondingday/timewillbe((11
1)*86400)+(4*3600)+(21*60)+1=879661secondsintothemonth
A.3.2 OptionalParameters
TheBasicObservationSequencemaybeamendedwithoptionalparameters,iftheyareavailable.
OptionalparametersareassignedaHeaderIndicator(A,B,Cetc.)Thisletterisusedintheheaderto
indicatethatthebasicobservationsequenceisfollowedbyoneormoreoptionalparameter.Foreach
optionalparameterthatisaddedtothebasicobservationsequence,theHeaderIndicatorassociated
withtheoptionalparametershallbeaddedinline2intheheader.Thesequenceoftheletters
determinestheorderinwhichtheoptionalparametersareadded.A#inline2indicatesnoadditional
parametersfollowthebasicobservationsequence.
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OptionalparametersaredescribedinTable16
Table16:AOSFRSOptionalParametersFormat
below.Allparametersshallberightjustified.
HEADERINDICATOR
#OFCHAR
CONTENT
FORMAT
NOTES
EXAMPLE
A 1 ROLLANGLEFLAG N SEEPARAGRAPH3.2.4.4 U
B 1OR9 EDR C
ORCNNNNNNNN
E12345678
C 3 DEVG NNN 7
D 3 TRUEAIRSPEED NNN 854
E 3 TRUEHEADING NNN 145
F GNSSALTITUDE NNNN 3750
G 1 ANTIICE(ENGINEORWINGORBOTH?) N 1 1
H 2 A/CCONFIGURATIONINDICATOR NN SEEPARAGRAPH0 01
I 6 WATERVAPOR NNNNNQ SEEAPPENDIXC.2ORCIMO? 123450
J
6
RELATIVE
HUMIDITY
NNNNNQ
SEE
APPENDIX
C.2
OR
CIMO?
05000U
K 1 ICING N 2 1
Notes
1.Antiice
Antiiceshallbereportedusingthefollowinglogic:
1 = Antiicenotactivated
2 = Antiiceactive
/ = Antiiceundeterminedorinvalid:
2.Icing
Icingwillbereportedasvalue1whentheaircrafticingsensorindicatesnoiceaccretion,asvalue2when
thesensorindicatesiceaccretionisoccurring,andasvalue0whenthestatusoficingisnotabletobe
determined(noterequiresseparatesysteminstalled,movenotetotable3inCH3)
Example1
Amessagewithonlythebasicobservationsequencewouldlookasfollows:
A4#AZ0001N1PEHAMKJ FKR- 2976 6081 8796613899- 525160 25R- 2976 6081 8796613899- 525160 25R- 2976 6081 8796613899- 525160 25
R- 2976 6081 8796613899- 525160 25R- 2976 6081 8796613899- 525160 25R- 2976 6081 8796613899- 525160 25R- 2976 6081 8796613899- 525160 25D- 2976 6081 8796613899- 525160 25D- 2976 6081 8796613899- 525160 25D- 2976 6081 8796613899- 525160 25
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Thisindicatesthattheobservationsinthemessagearebasicobservationsonly,aircraftAZ0001isflying
fromAmsterdamtoNewYork,thedataisnotcompressedandtheobservationsinascentanddescent
arebasedonthepressurescheme,usingBarometricaltitude.
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Example2:
GNSSandAntiiceareavailableandareaddedtothebasicobservationsequence.Amessagewould
thenlookasfollows
A04FGAZ0001N1BEHAMKJ FKA- 2976 6081 8796613899- 525160 25U38540A- 2976 6081 8796613899- 525160 2538540A- 2976 6081 8796613899- 525160 2538540A- 2976 6081 8796613899- 525160 2538540A- 2976 6081 8796613899- 525160 2538540A- 2976 6081 8796613899- 525160 2538540A- 2976 6081 8796613899- 525160 2538540
A- 2976 6081 8796613899- 525160 2538540A- 2976 6081 8796613899- 525160 2538540R- 2976 6081 8796613899- 525160 2538540
ThisindicatesthattheobservationsinthemessagearebasicobservationsamendedwithGNSSandAnti
iceinformation,aircraftAZ0001isflyingfromAmsterdamtoNewYork,thedataisnotcompressedand
theobservationsinascentanddescentarebasedonthepressurescheme,usingBarometricaltitude.
Example3:
WaterVapor,TrueAirspeed,Antiice,A/CconfigandEDRareavailableandaddedtothebasic
observationsequence,inthatorder.Themessagewouldlooklike:
A04I DGHBNL0032N0BWMKKYMMLA- 2976 6081 8796613899- 525160 25123450854101E12345678A- 2976 6081 8796613899- 525160 25123450854101E12345678R- 2976 6081 8796613899- 525160 25123450854101E12345678R- 2976 6081 8796613899- 525160 25123450854101E12345678R- 2976 6081 8796613899- 525160 25123450854101E12345678R- 2976 6081 8796613899- 525160 25123450854101E12345678R- 2976 6081 8796613899- 525160 25123450854101E12345678R- 2976 6081 8796613899- 525160 25123450854101E12345678D- 2976 6081 8796613899- 525160 25123450854101E12345678D- 2976 6081 8796613899- 525160 25123450854101E12345678
ThisindicatesthattheobservationsinthemessagearebasicobservationsamendedwithWaterVapor,
TrueAirspeed,Antiice,A/CconfigurationandEDRinformation,aircraftNL0032isflyingfromKuala
Lumpur toMelbourne,thedataisnotcompressedandtheobservationsinascentanddescentare
basedonthetimebasedscheme,usingBarometricaltitude
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AppendixB AOSFRSConfigurationMessageAconfigurationmessagecanberequestedtoallowausertocheckthecurrentstatusofthe
configurationparametersusedbytheAOS.Theconfigurationmessageisonlyrequiredwhenitcanactuallyberetrievedfromtheaircraftsomehow.Adetaileddescriptionisgivenbelow.
SA4
I AI A DDDDAAAA Sp AsI phAaG:IsgA:IsaT:Ist
AI ntA1/N/I nt
A2RI nt
RDI nt
D1/ I nt
D2
TOCTL1
TODTL2
H1H2H3H4
BBN
LatY1/Lat
Y2Long
X1/Long
X2S
BBB
NLat
Y1/Lat
Y2Long
X1/Long
X2S
B
BBN
LatY1/Lat
Y2Long
X1/Long
X2S
BBB
NLat
Y1/Lat
Y2Long
X1/Long
X2S
B
BBN
LatY1/Lat
Y2Long
X1/Long
X2S
BBB
NLat
Y1/Lat
Y2Long
X1/Long
X2S
B
BBN
LatY1/Lat
Y2Long
X1/Long
X2S
BBB
NLat
Y1/Lat
Y2Long
X1/Long
X2S
B
BBN
LatY1/Lat
Y2Long
X1/Long
X2S BB
NLat
Y1/Lat
Y2Long
X1/Long
X2S
B
B
A1I CAON/S
AA5I CAO
N/S
AA9I CAO
N/S
AA13I CAO
N/S
AA17I CAO
N/S
A
A2I CAON/S
AA6I CAO
N/S
A10I CAO
N/S
A14I CAO
N/S
A18I CAO
N/S
A A A A
A3 I CAON/S
AA7 I CAO
N/S
AA11I CAO
N/S
AA15I CAO
N/S
AA19I CAO
N/S
A
A4 I CAON/S
AA8 I CAO
N/S
AA12I CAO
N/S
AA16I CAO
N/S
AA20I CAO
N/S
A
TheBoldand/charactersarefixedcharacters.
Table
17:
AOSFRSconfigurationmessage
contents
PARAMETER DESCRIPTION FORMAT NOTES EXAMPLE
SA04 STATUSFORAOSFRSMESSAGEVERSION AAAA SA04
I AI A AMDARIDENTIFIER(MAX8CHARACTERS) AAAAAAAA AU0013
DDDD DEPARTUREAIRPORT AAAA ICAOCODE EHAM
AAAA ARRIVALAIRPORT AAAA ICAOCODE KJFK
SP PRESSUREBASED(P)ORTIMEBASED(T)SCHEME A P
AS AMDARSWITCHSETTING N 7
IPH FLIGHTPHASEATTIMEOFREQUEST A 1 A
AA AMDARACTIVEATTIMEOFREQUEST(Y/N) A 2 Y
ISG GEOGRAPHICALINRANGEATTIMEOFREQUESTY/N A N
ISA AIRPORTACTIVEATTIMEOFREQUESTY/N A Y
IST TIMEWINDOWACTIVEATTIMEOFREQUEST A Y
INTA1 OBSERVINGINTERVALDURINGASCENTPART1,INHPAORSECONDS NN 10
N NUMBEROFOBSERVATIONSMADEDURINGASCENTPART1 NN 10
INTA2 OBSERVINGINTERVALDURINGASCENTPART2,INHPAORSECONDS NN 50
INTR OBSERVINGINTERVALDURINGLEVELFLIGHTINSECONDS NNN 420
INTD1 OBSERVINGINTERVALDURINGDESCENTPART1,INHPAORSECONDS NN 50
INTD2 OBSERVINGINTERVALDURINGDESCENTPART2,INHPA NN 10
TL1 TOPOFCLIMBSETTINGINTHOUSANDSOFFEET NNNN 2000
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TL2 TOPOFDESCENTSETTINGINTHOUSANDSOFFEET NNNN 2000
H1H2H3H4 TIMEWINDOWSETTING NNNN 0000
BN GEOGRAPHICALBOXNUMBER(0TO9) N 1
LATY1 LATITUDEVALUEY1APPLIEDTOBOXBNINDEGREES SNN 30
LATY2 LATITUDEVALUEY2APPLIEDTOBOXBNINDEGREES SNN 50
LONGX1 LONGITUDEVALUEX1APPLIEDTOBOXBNINDEGREES SNNN 40
LONGX2 LONGITUDEVALUEX2APPLIEDTOBOXBNINDEGREES SNNN 120
SB STATUSOFBOXBN(1=REPORTINGACTIVE, 0=REPORTING
DISABLED)
N 1
ICAON ICAOCODEOFAIRPORTNUMBERAN AAAA EHAM
SA STATUSOFAIRPORT(1=REPORTINGACTIVE,0=REPORTING
DISABLED)
N 1
Notes:
1. Flightphasecharacters
G = Ground
A = Ascent
R = Enroute
D = Descent
2. AMDARactiveshowsifAMDARisreporting,asfollows
Y = AMDARisreporting
N = AMDARisinactive
MessageExample
SA04AU0113 EHAMKJ FK P 7 A Y G:0A:1 T:1
A10/ 10/ 50R420 D50/ 10TOC 20TOD20 0000B060/ 20 - 100/ 601 B5 0/ 0 0/ 0 0B1 0/ 0 0/ 0 0B6 0/ 0 0/ 0 0B2 0/ 0 0/ 0 0B7 0/ 0 0/ 0 0B3 0/ 0 0/ 0 0B8 0/ 0 0/ 0 0B B9 0/ 0 0/ 0 04 0/ 0 0/ 0 0
A1 EHAM/ 1A5 0000/ 0A9 0000/ 0A130000/ 0A170000/ 0A2KJ FK/ 0A6 0000/ 0A100000/ 0A140000/ 0A180000/ 0A A A A A3 0000/ 0 7 0000/ 0 110000/ 0 150000/ 0 190000/ 0A4 0000/ 0A8 0000/ 0A120000/ 0A160000/ 0A200000/ 0
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AppendixC OptionalDerivedParametersThisappendixdescribesthederivationforparametersthatarenotpartofthebasicobservation
sequence.
C.1 Turbulence
C.1.1 DerivedEquivalentVerticalGust
TheDerivedEquivalentVerticalGustVelocity(DEVG)isaturbulenceindicatordefinedasthe
instantaneousverticalgustvelocitywhich,superimposedonasteadyhorizontalwind,wouldproduce
themeasuredaccelerationoftheaircraft.Theeffectofagustonanaircraftdependsonthemassand
othercharacteristics,butthesecanbetakenintoaccountsothatagustvelocitycanbecalculatedwhich
isindependentoftheaircraft.
TheinformationbelowisanextractfromtheAustralianDepartmentofDefence,StructuresReport418,
TheAustralianImplementationofAMDAR/ACARSandtheuseofDerivedEquivalentGustVelocityasa
TurbulenceIndicator,DouglasJ.Sherman,1985.
Thevelocityofthederivedequivalentverticalgust,U ,(intenthsofmeterspersecond)maybe
calculatedbytheformula:
de
V
nAmDEVG
=10
wheren = peakmodulusvalueofdeviationofaircraftnormalaccelerationfrom1ginunitsofg.
m= totalaircraftmassin(metric)tonnes
V= calibratedairspeedatthetimeofoccurrenceoftheaccelerationpeak,inknots.
A= Anaircraftspecificparameterwhichvarieswithflightconditions,andmaybeapproximatedbythe
following
formulae:
A A c A cm
m= +
4 5 1( )
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A cc
c H kft = +
+12
3 ( )
=ValueofAwhenmassofaircraftequalsreferencemass
H= altitudeinthousandsoffeet
m= Referencemassofaircraftin(metric)tonnes
Theparameters dependontheaircraft'stypicalflightprofile.Forvariousaircraft,the
appropriateconstants,basedontheflightprofilesindicated,areshownin
c c c1 2 5, , ,K
Table18.
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Table18:DEVGaircraftconstants
Aircraft V1 Vc Mc h1 hc m c1 c2 c3 c4 c5
knot knot Mach ft ft Tonne kft
A300B4 130 300 0.78 5000 30000 120 0.971 2690 79 0.49 19.6
A310 130 300 0.78 5000 35000 120 19.6 574 32 0.52 23.5
A318 120 300 0.78 5000 35000 40 34.7 878 28 0.52 40.3
A319 120 300 0.78 5000 35000 50 33.9 846 29 0.45 39.6
A320-200 120 300 0.78 5000 35000 55 35.9 771 27 0.44 40.7
A321 120 300 0.78 5000 35000 60 34.8 716 28 0.41 39.3
A330-200 120 300 0.82 5000 35000 170 5.88 1010 55 0.44 13.7
A330-300 120 300 0.82 5000 35000 170 5.89 1010 54 0.44 13.6
A340-200 120 300 0.82 5000 35000 190 6.36 949 54 0.41 13.7
A340-300 120 300 0.82 5000 35000 190 6.34 948 54 0.41 13.6
B727 120 300 0.84 5000 30000 50 6.45 4580 83 0.54 37.3
B737-200 120 300 0.73 3000 35000 30 62.0 351 14 0.64 59.4
B737-300 120 300 0.73 3000 35000 40 56.4 328 15 0.56 54.7
B737-400 120 300 0.73 3000 35000 40 56.3 329 15 0.56 54.5
B737-500 120 300 0.75 3000 35000 40 56.4 303 14 0.57 54.3
B737-600 120 300 0.78 3000 35000 40 45.4 420 18 0.57 45.3
B737-700 120 300 0.78 3000 35000 50 42.4 374 19 0.54 42.4
B737-800 120 300 0.78 3000 35000 50 42.2 350 18 0.57 41.9
B747-200 140 300 0.85 5000 40000 250 -2.41 2230 97 0.65 11.5
B747-300 140 300 0.85 5000 40000 200 2.27 1630 81 0.69 13.3
B747-400 140 300 0.85 5000 40000 250 -7.78 3260 120 0.62 10.2
B747SP 140 300 0.85 5000 40000 250 7.44 644 48 0.74 12.4
B757-200 140 300 0.8 3000 40000 100 29.2 298 22 0.55 30
B757-300 140 300 0.8 3000 40000 100 28.9 292 21 0.55 29.7
B767-200 140 300 0.8 3000 40000 110 12.8 918 46 0.65 19.8
B767-300 140 300 0.8 3000 40000 100 13.1 821 42 0.69 19.4
B767-400 140 300 0.8 3000 40000 150 12.9 701 45 0.54 18.3
B777-200 140 300 0.82 3000 40000 170 12.6 198 21 0.72 13.0
B777-300 140 300 0.82 3000 40000 210 13.1 147 19 0.65 12.9
BAC111-200 120 280 0.7 3000 30000 30 55.8 924 27 0.54 60.1
BAC111-475 120 280 0.7 3000 30000 30 50.6 930 28 0.54 55.3
DC10-30 150 300 0.82 5000 30000 200 -6.45 4080 130 0.56 15.0
Electra 100 350 0.7 5000 30000 30 48.9 220 9.1 0.57 41.2
Fokker-100 130 280 0.7 3000 30000 35 52.9 917 27 0.52 57.2
KingAir 100 110 200 0.6 9000 25000 3 70.6 2280 89 0.74 223.
L1011-500 120 300 0.83 5000 35000 150 11.7 712 47 0.59 17.1
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C.1.2 EddyDissipationRate(EDR)
DetailsoftheEDRalgorithmandtheencodingprocesswillbeprovidedinafuturesupplementtothis
standard.
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C.2 AtmosphericWaterVaporContent
Dependingonthewatervaporsensorinstalled,thesoftwarewillbecapableofreportingatmospheric
watervaporcontentfordownlinkin3ways:
1. Mixingratio(r):definedtobetheratioofthemassofwatervaporcontenttothemassofdryair
ofanairsample.Theunitsofrareg/kg.
Resolution:1x103
g/kg.
Range:0to38g/kg.
2. Relativehumidity(RH):definedtobethedensityofwatervaporpresentintheatmosphere
expressedasapercentageofthedensityofwatervaporpresentwhentheairsampleis
saturated(airpressureandtemperatureheldconstant).Thatis:
RH=100x(densityofactualwatervapor/densityofsaturatedwatervapor)
Resolution:0.1%.
Range:0to100%
3. Dewpointtemperature(DPT):thetemperaturetowhichairmustbecooledinorderforitto
becomesaturated(airpressureheldconstant.TheunitsofDPTaredegreesCelsius(C).
Resolution:0.1C
Range: 99to49C
Thesoftwarewillrequireaconfigurationparametertodeterminefromwhichsensorthewatervapor
contentshouldbeacquiredand,asaconsequence,howthewatervaporcontentshouldbeencoded.
WatervaporcontentwillbereportedinthedownlinkmessageasnnnnnQ.Wherennnnisthecoded
watervaporcontentandQisaqualitycontrolparameter.ThevalueofQwillbedependentonthetype
ofsensoremployedandtheunitsinwhichthewatervaporcontentisreported.
Table19:WaterVapourConfigurationCriteria
WATERVAPORSENSOR CONFIGURATIONPARAMETER DOWNLINKFORMAT(NNNNN) QCFORMAT(Q)
NONE 0 ///// 9
WVSSII 1 MIXINGRATIO SEETABLE20
? 2 HUMIDITY U
? 3 DEWPOINTTEMPERATURE D
Inordertoobtainthehighestqualitywatervaporcontentdataontheground,itisalwayspreferableto
downlinkthewatervaporsensoroutputvariableasprovidedratherthanconvertingtooneofthetwo
alternativederivedvariables,e.g.ifthesensorprovidesmixingratio,thenthatiswhatshouldbe
reportedratherthanconvertingtorelativehumidityordewpointtemperatureforreporting.
AtthetimethisspecificationwaspreparedonlydetailsontheWVSSIIsensorwereknown.
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C.2.1 TheWVSSIISensor
C.2.1.1 Introduction
ThesecondgenerationWaterVaporSensingSystem(WVSSII)forcommercialaircraftusesadiodelaser
fortheaccuratemeasurementofwatervaporinformation.Thewatervaporinformationavailableisthe
massatmosphericwatervapormixingratioinkilogramsperkilogram(kg/kg).
TheWVSSIIhasaSystemsElectronicsBox(SEB)thatsendsthemixingratioinARINC429message(Octal
Label303)andbitsinOctalLabel270(relatedtoQvalues)totheavionicsbox(DFDAUorequivalent).
FirststepistocheckthestatusbitsinARINC429messageLabel270(seeSectionC.2.1.4below).If,asa
resultofthestatusbitchecks,theQvaluehasbeensetto2,3,4,or5,thennocalculationismadeand
thedatavaluesformixingratioaresetto(/////)asinSectionsC.2.1.3andC.2.1.4 below.
Ontheotherhand,iftheQvaluehasnotbeensetbytheabovebitchecking,thentheQvalueissetto0
andcalculationsproceedasinSectionC.2.1.2below.Theencodingofthemixingratiovaluethen
proceedsasinSectionC.2.1.3below.
C.2.1.2 CurrentInputVariablesandCalculation
ThevariablesthatareinputtotheprocessingintheDFDAUareasfollows:
Ts: statictemperatureexpressedindegreesKelvin;i.e.,add273.15todegreescentigrade
Ps: staticpressureexpressedinPascals;i.e.,ifpressureinmillibarsorhPa,thenmultiplyby100
NotethatthismaybeobtainedasSTATICPRESSUREorcalculatedfromPRESSUREALTITUDE.
r: (mixingratioinkg/kg). ObtainedfromdiodelaseroftheWVSSIIissuppliedindigitalformtothe
DFDAUatarateofonceeverytwoseconds.
Themixingratioisusedintheobservationbuttherelativehumidity(RH)isusedasacontrolvariable.
Withtheaboveinputvariables,thecalculationofRHisperformedonceeverytwoseconds(usingthe
latestpressureandtemperature)asfollows:
Step1: Calculatewatervaporpressure(e)fromequation(1)
e = (Ps) ( r )/ (r + 0.62197) (1)
Step2: Calculatesaturationvaporpressure(es)fromequation(2)
es= 10 ** [(10.286 Ts 2148.909) / (Ts 35.85)] (2)
Step3: CalculateRHfromequation(3)
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RH = (e/es)(100) (3)
Step4:RoundtheRHvaluetothenearestinteger
Add0.5tothefloatingpointRHvalue,andthentruncatethevaluetoaninteger.
Step5: IFRHlessthan101%,THEN
(i) Presentthemixingratiointhe5charactercode(NNNNN)accordingtoSectionC.2.1.3below.
(ii) Set the control character (Q) in the water vapor information field (NNNNNQ) to Q = 0 (see
SectionC.2.1.4below).
IFRHequaltoorgreaterthan101%,THEN
(i) Presentthemixingratiointhe5charactercode(SectionC.2.1.3below)
(ii) SetQ=1(SectionC.2.1.4below)
C.2.1.3 Presentingthe5-characterMixingRatioField
ThemassmixingratioisbroadcastfromthespectraSensorsWVSSIIsensoronARINC429label303.For
detailedinformationseeSpectraSensorsDWGNo.0102100027,REV.C
ThemassmixingratioiscomputedwithintheWVSSIIsoftwareasafloatingpointnumberinkg/kg.In
ordertorepresentthisnumberasanintegervariableinthe32bitARINCword,thisnumberismultiplied
by220andsendtotheavionicsbox.Soinordertousethevalueneedstobedividedby2
20beforethe
datacanbeencoded.
Thewatervaporinformationispresentedasasixcharacterfield(NNNNNQ)wherethefirstfive
charactersareintegers(NNNNN)withthefollowingmeaning:
NNNNN = N1N2N3N4N5= N1 N2 N3 N4x 10(-3 N5)
Example:12345=1234x1035 =1234x108kg/kg
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C.2.1.4 TheQualityControlCharacter(Q)
ThevalueQisaqualitycontrolcharacteranditsultimatenaturehasthemeaningdefinedintheTable
below.
Table20
:WVSII
Quality
Control
Parameter
Q SystemState SoftwareLogic DataOutput
0 Normaloperation Air/Ground=Air NNNNN0
1 RHgreaterthanorequalto101% RH>thanor=to101% NNNNN1
2 Inputlaserpowerlow Laser
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(/////)andtheQissetto8sothe6charactercodeis/////8.
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AppendixD DataCompression
Inordertominimizethenumberofcharacterinamessageandtherebytransmissioncost,twocodingtechniquesareappliedtothemessagecontents.Thefirsttechniquecodescodessomenumericvalues
intheremainingobservationsasdeltachangesfromtheirpreviousvaluesthisisasavingbecausemost
ofthequantitiesarephysicalvaluesthatvaryslowlywithtime. Thesecondtechniquecodesallinteger
numericvaluesinthemessageintothefullsetofavailableprintablecharacterse.g.arangeof19to
+20canbemappedonto40printablecharacters,thesocalledbase40compression.
D.1 Base-40Compression
Abase40datacompressionschemecanbeappliedtotheintegervaluesinthemessage.Theinteger
valuesaremappedto40printablecharactersaccordingtoTable21
Table21:Base40ConversionChart
.
0 1 2 3 4 5 6 7 8 9
0X 0 1 2 3 4 5 6 7 8 9
1X A B C D E F G H I J
2X K L M N O P Q R S T
3X U V W X Y Z : , .
Findtherangethatthevaluetocompresswillfallinto. [0(40^y)/2,(40^y)/21]willbetheformoftherange,whereyisthesmallestinteger=>1tomakethevaluetocompressfallintotherange
(seeTable22).Addthebase40offsetprovidedinNotes:
1. TheAMDARidentifierisassignedbytherequestingmetoffice.
2. Normal means the data is not compressed. Compressed means the data is encoded using the
compressionschemedescribedinAppendixD.
3. PressureAltitudeinICAOStandardAtmosphere=PALT;
BarometricAltitudeinQNHadjustedatmosphere=BALT;
IfBALTisreported,conversiontothePressureAltitude(PALT)scalewillbenecessaryingroundprocessing
usingrunwayorareaQNHatthetimeoftheobservation.Thisisessentialbeforedatacanbeusedor
exchanged.IfbothPALTandBALTareavailable,PALTispreferred.
4. DepartureandArrivalairportarerepresentedbytheirICAOcode.Reportingofthesefieldsisoptionalbut
ifavailable,stronglyrecommended.
Table24and
.Thebase40offsetisaddedtotheintegervaluetoensureonlypositiveintegers.Table25
Takethenewvalueandconverttoabase40characterstring.
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Table22:DynamicRanges
CHARACTERSREQUIRED(YVALUE) MINIMUMVALUE MAXIMUMVALUE
1 20 19
2 800 799
3 32,000 31,999
4 1,280,000 1,279,9995 51,200,000 51,199,999
6 2,048,000,000 2,047,999,999
Importantitemstonote
Valuesoutsideoftherange[2,048,000,000..2,047,999,999]cannotbeconvertedandshallreturn/;
Decompressingastringcontainingnonvalidcharacterswillreturn2147483647;
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D.2 Messageformat,Compressed
WhenapplyingdeltaBase40theformatforthemessageformatchangesasfollows:
Table23:Header,compressed
LINE
NUMBER
CHARACTER
NUMBER
#OFCHAR CONTENT FORMAT NOTES
1 13 3 AMDARMESSAGEVERSION A04
2 126 1TO26 OPTIONALPARAMETERINDICATION #ORATHRUZ SEEOPTIONAL
PARAMETERS
3 17 8 AMDARAIRCRAFTIDENTIFIER AAAAAAAA 1
3 8 1 NORMAL(N)ORCOMPRESSED(C) NORC 2
3 9 1 TIMEBASED(0)ORPRESSUREBASEDSCHEME
(1)
0OR1
3 10 1 ALTITUDEREFERENCE:PRESSUREALTITUDE
(P)ORBAROMETRICALTITUDE(B)
PORB 3
3
1114
4
DEPARTUREAIRPORT
AAAA
4
3 1518 4 ARRIVALAIRPORT AAAA 4
Notes:
5. TheAMDARidentifierisassignedbytherequestingmetoffice.
6. Normal means the data is not compressed. Compressed means the data is encoded using the
compressionschemedescribedinAppendixD.
7. PressureAltitudeinICAOStandardAtmosphere=PALT;
BarometricAltitudeinQNHadjustedatmosphere=BALT;
IfBALTisreported,conversiontothePressureAltitude(PALT)scalewillbenecessaryingroundprocessing
usingrunwayorareaQNHatthetimeoftheobservation.Thisisessentialbeforedatacanbeusedor
exchanged.IfbothPALTandBALTareavailable,PALTispreferred.
8. DepartureandArrivalairportarerepresentedbytheirICAOcode.Reportingofthesefieldsisoptionalbut
ifavailable,stronglyrecommended.
Table24:BasicObservationFormat,compressed
CHARACTERSDESCRIPTION TYPE BASE40
OFFSET
ABSOLUTE
RANGE
DELTA
ALLOWED
RANGE FIRST
OBS
SUBSEQOB
S
PHASEOFFLIGHTINDICATOR 10XABSOLUTE N/A N/A N/A 1 1
LATITUDE(INSECONDS) 1XABSOLUTE
9XDELTA
1,280,000
32,000
324000TO
+324000
SECONDS
32000
TO
+31999
SECONDS
4 3
LONGITUDE(INSECONDS) 1XABSOLUTE
9XDELTA
1,280,000
32,000
648000TO
+648000
SECONDS
32000
TO
+31999
SECONDS
4 3
DAY/TIME(UTC) 1XABSOLUTE 0 0TO 0TO 5 3
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9XDELTA 0 2678399
SECONDSINTO
THEMONTH
32000
SECONDS
PRESSUREALTITUDEINTENSOFFEET
(REFERENCESAGAINSTSTANDARD
ICAOATMOSPHERE)
10XABSOLUTE 32,000 100TO
+5,000TENS
OFFEET
N/A 3 3
TEMPERATURE 10XABSOLUTE 800 800TO+799TENTHSOFC
N/A 2 2
WINDDIRECTION 10XABSOLUTE 0 0TO360
DEGREES
N/A 2 2
WINDSPEED 10XABSOLUTE 0 0TO+800
KNOTS
N/A 2 2
TOTALS 23 19
Table25:Optionalparameters,compressed
CHARACTERSDESCRIPTION TYPE BASE40
OFFSET
ABSOLUTE
RANGE
DELTA
ALLOWED
RANGE FIRST
OBS
SUBSEQOB
S
ROLLANGLEFLAG 10XCHARACTER 0 N/A N/A 1 1
EDR 10XCHARACTER N/A N/A N/A 1+8*
1+8*
DEVG 10XABSOLUTE 0 0TO800
TENTHSM/SEC
N/A 2*
2*
TRUEAIRSPEED 10XABSOLUTE 0 0TO999 N/A 3 3
TRUEHEADING(TENTHOFDEGREES) 10XABSOLUTE 0 0TO3590 N/A 3 3
GNSSALTITUDE 10XABSOLUTE 0 100TO
+5,000TENS
OFFEET
N/A 3 3
ANTIICE 10XABSOLUTE 0 0TO2 N/A 1 1
A/CCONFIGURATIONINDICATOR 10XABSOLUTE 0 OTO15 N/A 1 1
WATERVAPOR 10XABSOLUTE 0 0TO99999 N/A 4 4
WATERVAPORQUALITY 10XCHARACTER N/A N/A N/A 1 1
ICING 10XABSOLUTE 0 0TO2 N/A 1 1
TOTALS 21+7*
21+7*
*ThenumberofcharactersdependsonwhetherEDRorDEVGischosenastheturbulenceindicator.IfEDRis
chosen,italsodependsthevalueforEDR.Inthesetotals,DEVGisassumed(2characters),ifEDRischosen,the
totalnumberwouldbe21+7=28