用英语介绍飞机

Whatisaircraft?

Anaircraftisamachinethatisabletoflybygainingsupportfromtheair.Itcounterstheforceofgravitybyusingeitherstaticliftorbyusingthedynamicliftofanairfoil,orinafewcasesthedownwardthrustfromjetengines.

Thehumanactivitythatsurroundsaircraftiscalledaviation.Crewedaircraftareflownbyanonboardpilot,butunmannedaerialvehiclesmayberemotelycontrolledorself-controlledbyonboardcomputers.Aircraftmaybeclassifiedbydifferentcriteria,suchaslifttype,aircraftpropulsion,usageandothers.

Thehistoryofaircraft:

Flyingmodelcraftandstoriesofmannedflightgobackmanycenturies,howeverthefirstmannedascent–andsafedescent–inmoderntimestookplacebylargerhot-airballoonsdevelopedinthe18thcentury.EachofthetwoWorldWarsledtogreattechnicaladvances.Consequently,thehistoryofaircraftcanbedividedintofiveeras:

Pioneersofflight,fromtheearliestexperimentsto1914.

FirstWorldWar,1914to1918.

AviationbetweentheWorldWars,1918to1939.

SecondWorldWar,1939to1945.

Postwarera,alsocalledthejetage,1945tothepresentday.

Impactsofaircraftuse:

Aircraftpermitlongdistance,highspeedtravelandmaybeamorefuelefficientmodeoftransportationinsomecircumstances.Aircrafthaveenvironmentalandclimateimpactsbeyondfuelefficiencyconsiderations,however.Theyarealsorelativelynoisycomparedtootherformsoftravelandhighaltitudeaircraftgeneratecontrails,whichexperimentalevidencesuggestsmayalterweatherpatterns.

Usesforaircraft:

1.Military

Amilitaryaircraftisanyaircraftthatisoperatedbyalegalorinsurrectionaryarmedserviceofanytype.Militaryaircraftcanbeeithercombatornon-combat.

2.Civil

Civilaircraftdivideintocommercialandgeneraltypes,howevertherearesomeoverlaps.

Commercialaircraftincludetypesdesignedforscheduledandcharterairlineflights,carryingpassengers,mailandothercargo.Thelargerpassenger-carryingtypesaretheairliners,thelargestofwhicharewide-bodyaircraft.Someofthesmallertypesarealsousedingeneralaviation,andsomeofthelargertypesareusedasVIPaircraft.

Generalaviationisacatch-allcoveringotherkindsofprivate(wherethepilotisnotpaidfortimeorexpenses)andcommercialuse,andinvolvingawiderangeofaircrafttypessuchasbusinessjets(bizjets),trainers,homebuilt,gliders,warbirdsandhotairballoonstonameafew.Thevastmajorityofaircrafttodayaregeneralaviationtypes.

3.Experimental

Anexperimentalaircraftisonethathasnotbeenfullyproveninflight,orthatcarriesanFAAairworthinesscertificateintheExperimentalcategory.Often,thisimpliesthattheaircraftistestingnewaerospacetechnologies,thoughthetermalsoreferstoamateurandkit-builtaircraft—manybasedonprovendesigns.

4.Model

Amodelaircraftisasmallunmannedtypemadetoflyforfun,forstaticdisplay,foraerodynamicresearchorforotherpurposes.Ascalemodelisareplicaofsomelargerdesign.