BlackBox
Youneverseethembutthey'rewithyoueverytimeyoufly.Theyrecordwhereyou'regoinghowfastyou'retravelingandwhethereverythingonyourairplaneisfunctioningnormally.Theirabilitytoresistalmostanydisastermakesthemseemlikesomethingoutofacomic(漫画) book.They'reknownastheblackbox.
WhenplanesfallfromtheskyasaYemeniairlinerdidonitswaytotheComorosIslandsintheIndianOceanonJune302009theblackboxisthebestmethodforidentifyingwhatwentwrong.SowhenaFrenchsubmarine(潜水艇) discovereditshomingsignalfivedayslateritmarkedahugesteptowarddeterminingthecauseofthedisasterinwhich152passengerswerekilled.
In1958.AustralianscientistDavidWarrendevelopedaflight-memoryrecorderthatwouldtrackbasicinformationlikealtitudeanddirection.ThatwasthefirstmodelforablackboxwhichbecamearequirementonallUScommercialflightsby1960.Earlymodelsoftenfailedtoresistcrasheshoweversoin1965itwascompletelyredesigned.ThatsameyeartheFederalAviationAuthorityrequiredthattheboxeswhichwereneveractuallyblackbepaintedorangeoryellowtobeeasiertosee.
Modemairplaneshavetwoblackboxes:avoicerecorderwhichtrackspilots'conversationsandaflight-datarecorderwhichmonitorsfuellevelsenginenoisesandotheroperatingfunctionsthathelpexpertsreconstructtheaircraft'sfinalmoments.Theboxescanresistpowerfulforceandtemperaturesupt02OOOoF.They'realsoabletosendoutsignalsfromdepthsof20000ft.ExpertsbelievetheboxesfromAirFranceFlight447 whichcrashednearBrazilonJune12009 areinwaternearlythatdeepbutstatisticssaythey'restilllikelytoturnup.Intheapproximately20deep-seacrashesoverthepast30yearsonlyoneplane'sblackboxeswereneverrecovered.
【小题1】Whatcanweleamabouttheblackboxfromthepassage?