2020年度等级考试-英语四级-真题

evelopedaflight-memoryrecorderthatwouldtrackbasicinformationlikealtitudeanddirection.Thatwasthefirstmodeforablackbox,mercialflightsby1960.Earlymodelsoftenfailedtowithstandcrashes,however,pletelyredesignedandmovedtotherearoftheplane–thearealeastsubjecttoimpact–fromitsoriginalpositioninthelandingwells(起落架舱).Thesameyear,theFederalAviationAuthorityrequiredthattheboxes,whichwereneveractuallyblack,bepaintedorangeoryellowtoaidvisibility. Modernairplaneshavetwoblackboxes:avoicerecorder,whichtrackspilots'conversations,andaflight-datarecorder,whichmonitorsfuellevels,enginenoisesandotheroperatingfunctionsthathelpinvestigatorsreconstructtheaircraft'sfinalmoments.Placedinaninsulated(隔绝的)caseandsurroundedbyaquarter-inch-thickpanelsofstainlesssteel,theboxescanwithstandmassiveforceandtemperaturesupto2,000