Copying Birds May Save Aircraft FuelBoth Boeing and Airbus have trumpeted the efficiency of their newest aircraft.The 787 and 350 respectively.Their clever designs and lightweightcompositescertainly make a difference.But a group of researchers at Stanford University,led by Ilan Kroo,has suggested that airlines could take a more naturalisticapproach to cutting jet-fuel use and it would not require them to buy newaircraft.The answer,says Dr Kroo,lies with birds.Since 1914,scientists have known thatbirds flying in formation-a V-shape-expend less energy.The air flowing over abird's wings curls upwards behind the wingtips.a phenomenon known asupwash.Other birds flying in the upwash experience reduced drag,and spendless energy propelling themselves.Peter Lissaman,anaeronautics expert whowas formerly at Caltech and the University of Southern California,has suggestedthat a formation of 25 birds might enjoy a range increase of 71%.When applied to aircraft,the principles are not substantially different.Dr Krooand his team modeled what would happen if three passenger jets departing fromLos Angeles,San Francisco and I as Vegas were to assemble over Utah,assume aninverted V-formation occasionally change places so all could have a turn in themost favourable positions,and proceed to London.They found that the aircraftconsumed as much as 15%less fuel（coupled with a reduction in carbon-dioxideoutput）.Nitrogen-oxide emissions during the cruising portions of the flight fellby around a quarter.There are,of course,knots to be worked out.One consideration is safety,or atleast the perception of it.Would passengers feel comfortable travelling incompanion?Dr Kroo points out that the aircraft could be separated by severalnautical miles,and would not be in the intimate groupings favoured by displayteams like the Red Arrows,A passenger peering out of the window might noteven see the other planes.Whether the separation distances involved wouldsatisfy air-traffic-control regulations is another matter,although a working groupat the International Civil Aviation Organisation has included the possibility offormation flying in a blueprint for new operational guidelines.It remains to be seen how weather conditions affect the air flows that makeformation flight more efficient.In zones of increased turbulence,the planes'wakes will decay more quickly and the effect will diminish.Dr Kroo says this isone of the areas his team will investigate further.It might also be hard for airlinesto co-ordinate the departure times and destinations of passenger aircraft in a waythat would allow them to gain from formation flight.Cargo aircraft,in contrast,might be easier to reschedule,as might routine military flight.As it happens,America's armed forces are on the on case already.Earlier thisyear the country'S Defence Advanced Research Projects Agency announcedplans to pay Boeing to investigate formation flight,though the programme hasyet to begin.There are reports that some military aircraft flew in formation whenthey were low on fuel during the Second World War,but Dr Lissaman says theyare unsubstantiated."My father was an RAF pilot and my cousin the skipper of aLancaster lost over Berlin,"he adds.So he should know
Formation flight is more comfortable because passengers can not see theother plans.
错误
由题干关键词Formation flight is more comfortable可推测答案依据在原文第四段第三句。通过关键词passengers cannotsee the other planes则还可以回文定位其后本段第五句。第三句的passengers feel comfortable和本题的题干是同义替换,但是原文句子是一个疑问句,文中并未给出结论,因此并不能据此判断题干后半部分的原因是否正确。第五句话中的"might not"表示的是可能性,而题干的"cannot"表示的是事实。更重要的是文章的第五句话是为了说明第四句话Dr.Kroo points that the aircraft could be separated by several nautical miles,and would not be in the intimate groupings favored by display teams like theRed Arrows.本句主要强调飞机间距会比较大,第五句是来形象说明这个距离大到'乘客都看不到其他飞机”,而这个与是否舒服并没有明确的直接关系。再看本段第一句和第二句话,可知这里所谓的不舒服,其实就是指的不安全感。因为编队飞行时客机距离会很远，飞机乘客甚至看不到其他飞机的存在,就会觉得不安全。从常识可以判断出不安全感和舒适感是相反的，因此编队飞行更舒适这个命题是错误的。答案为F.
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