单选题 Both Boeing and Airbus have trumpeted the efficiency of their newest aircraft, the 787 and A350 respectively. Their clever designs and lightweight composites certainly make a difference. But a group of researchers at Stanford University, led by Ilan Kroo, has suggested that airlines could take a more naturalistic approach to cutting jet-fuel use, and it would not require them to buy new aircraft.
The answer, says Dr. Kroo, lies with birds. Since 1914, and a seminal paper by a German researcher called Carl Wieselsberger, scientists have known that birds flying in formation—a V-shape, echelon or otherwise—expend less energy. The air flowing over a bird's wings curls upwards behind the wingtips, a phenomenon known as upwash. Other birds flying in the upwash experience reduced drag, and spend less energy propelling themselves. Peter Lissaman, an aeronautics expert who was formerly at Caltech and the University of Southern California, has suggested that a formation of 25 birds might enjoy a range increase of 71%.
When applied to aircraft, the principles are not substantially different. Dr. Kroo and his team modeled what would happen if three passenger jets departing from Los Angeles, San Francisco and Las Vegas were to rendezvous over Utah, assume an inverted V-formation, occasionally swap places so all could have a turn in the most favourable positions, and proceed to London. They found that the aircraft consumed as much as 15% less fuel (with a concomitant reduction in carbon-dioxide output). Nitrogen-oxide emissions during the cruising portions of the flight fell by around a quarter.
There are, of course, kinks to be worked out. One consideration is safety, or at least the perception of it. Would passengers feel comfortable travelling in convoy'? Dr. Kroo points out that the aircraft could he separated by several nautical miles, and would not be in the unnervingly easy groupings favoured by display teams like the Red Arrows. A passenger peering out of the window might not even see the other planes. Whether the separation distances involved would satisfy air-traffic-control regulations is another matter, although a working group at the International Civil Aviation Organization has included the possibility of formation flying in a blueprint for new operational guidelines.
It remains to be seen how weather conditions affect the air flows that make formation flight more efficient. In zones of increased turbulence, the planes' wakes will decay more quickly and the effect will diminish. Dr. Kmo says this is one of the areas his team will investigate further. It might also he hard for airlines to coordinate the departure times and destinations of passenger aircraft in a way that would allow them to gain from formation flight. Cargo aircraft, in contrast, might be easier to reschedule, as might routine military flights.
As it happens, American's armed forces are on the ease already. Earlier this year the country's Defense Advanced Research Projects Agency announced plans to pay Boeing to investigate formation flight, though the programme has yet to begin. There are reports that some military aircraft flew in formation when they were low on fuel during the Second World War, hut Dr. Lissaman says they are apocryphal. "My father was an RAF pilot and my cousin the skipper of a Lancaster lost over Berlin," he adds. So he should know.

单选题 From the first two paragraphs, we can learn that ______.
A. energy cost reduced in a formation of V-shape and echelon or otherwise
B. 25 birds might enjoy 71% less energy consuming
C. a naturalistic airline works well than clever designs and lightweight composites
D. Kroo and his group are opposites who think that buying new aircraft is wasteful

单选题 Which of the following can support "the principles are not substantially different" ?
A. Three passengers were in the most favourable positions during the experiment.
B. 15% less fuel reduction in carbon-dioxide output and nitrogen-oxide emissions during flying.
C. Kroo and his team conducted their experiments in Los Angeles, San Francisco, Las Vegas, Utah and London.
D. Air crafts can occasionally swap places to turn in the most favourable positions as well as birds.

【正确答案】 B

【答案解析】[解析] 第三段第三句和第四句提到：他们发现飞机节省了多达15%的燃油，相应的二氧化碳排放量也减少了很多，途中排放的氮氧化物减少了约1/4。故B为答案。A中的passengers(乘客)和原文中的passenger jets(客机)是不同的，要仔细阅读，注意区分，故A错误。C的错误在于混淆地点和实验过程，第三段第二句提到：克鲁教授和他的团队模拟了三架分别从洛杉矶、旧金山和拉斯维加斯起飞的客机，在犹他州集合，采用反V字形状并偶尔换一下位置以便所有飞机轮流利用最有利的位置，最后飞到伦敦。而不是分别在这些地方做实验，故错误。D的错误在于以偏概全，不符合题于中“原理差异不大”的原因。

单选题 Which of the following best defines the word "kinks" ( Line 1, Paragraph 4) ?
A. Safety perception. B. Display teams.
C. Operational guidelines. D. Separation distances.

【正确答案】 C

【答案解析】[解析] 第四段第一句提到：当然，有个kinks将被制定出来。本句也是本段的中心句，之后的内容都在描述如何制定kinks。第二句提到：要考虑安全问题，至少在感觉上来说是安全的。第四句提到：克鲁教授指出飞机间会相隔几海里，不会像红箭表演队那样间距小得令人窒息。第六句提到：有关飞机间距是否符合空中管制条例暂且不谈，但国际民航组织的一个工作组已经考虑在新的操作方针中列入编队飞行的可能性。本句是解题的题眼根据。故c为正确答案，A、D选项都是考虑的因素，用个体代替整体。B选项只是举例，故排除。