Part B: True or False (2010)
Copying Birds May Save Aircraft Fuel
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, scientists have known that birds flying in formation—a V-shape—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 modelled what would happen if three passenger jets departing from Los Angeles, San Francisco and Las Vegas were to assemble over Utah, assume an inverted V-formation, occasionally change places so all could have a turn in the most favorable positions, and proceed to London. They found that the aircraft consumed as much as 15% less fuel (coupled with a reduction in carbon dioxide output). Nitrogen-oxide emissions during the cruising portions of the flight fell by around a quarter.
There are, of course, knots to be worked out. One consideration is safety, or at least the perception of it. Would passengers feel comfortable travelling in companion? Dr. Kroo points out that the aircraft could be separated by several nautical miles, and would not be in the intimate groupings favored 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. Kroo says this is one of the areas his team will investigate further. It might also be hard for airlines to co-ordinate 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, America’s armed forces are on the case 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, but Dr. Lissaman says they are unsubstantiated. “My father was an RAF pilot and my cousin the skipper of a Lancaster lost over Berlin,” he adds. So he should know.
Statements
41. Findings of the Stanford University researchers will promote the sales of new Boeing and Airbus aircraft.
[ T ] [ F ]
42. The upwash experience may save propelling energy as well as reducing resistance.
[ T ] [ F ]
43. Formation flight is more comfortable because passengers can not see the other planes.
[ T ] [ F ]
44. The role that weather plays in formation flight has not yet been clearly defined.
[ T ] [ F ]
45. It has been documented that during World War II, America’s armed forces once tried formation flight to save fuel.
[ T ] [ F ]
全文翻译
波音和空客都分别宣扬了其最新飞机787和A350的效率。它们巧妙的设计和轻质复合材料当然会起到作用。但斯坦福大学由伊兰·库鲁领导的一组研究人员提出，航空公司可以采取一种更仿生的方法来减少燃油使用，而且这不需要他们购买新飞机。
库鲁博士说，答案在于鸟类。自1914年以来，科学家就知道鸟类以编队——V字形——飞行消耗的能量更少。流过鸟翼的空气在翼尖后方向上卷曲，这种现象被称为上升气流。在上升气流中飞行的其他鸟类受到的阻力减小，用于推动自身的能量也更少。曾先后在加州理工学院和南加州大学工作的航空学专家彼得·利萨曼提出，25只鸟编队飞行可能使航程增加71%。
当应用于飞机时，原理没有本质区别。库鲁博士和他的团队模拟了如果三架分别从洛杉矶、旧金山和拉斯维加斯起飞的客机在犹他州上空汇合，采用倒V形编队，偶尔交换位置以便所有飞机都能在最有利的位置上轮换，然后飞往伦敦，会发生什么。他们发现飞机的油耗降低了多达15%（同时二氧化碳排放也减少了）。飞行巡航阶段的氮氧化物排放量下降了约四分之一。
当然，还有难题需要解决。一个考虑因素是安全，或者至少是安全感。乘客会愿意在伴飞中旅行吗？库鲁博士指出，飞机之间可以相隔数海里，不会像红箭飞行表演队青睐的那种紧密编队。乘客向窗外看甚至可能看不到其他飞机。涉及的间隔距离是否满足空中交通管制规定是另一回事，尽管国际民用航空组织的一个工作组已经在新操作指南的蓝图中包含了编队飞行的可能性。
天气条件如何影响使编队飞行更高效的气流还有待观察。在湍流增加的区域，飞机的尾迹会更快消散，效果也会减弱。库鲁博士说这是他团队将进一步研究的领域之一。航空公司可能也很难协调客机的起飞时间和目的地，使其能从编队飞行中获益。相比之下，货运飞机可能更容易重新调度，常规军事飞行也是如此。
碰巧的是，美国军方已经在处理此事了。今年早些时候，美国国防高级研究计划局宣布计划资助波音公司研究编队飞行，不过该计划尚未开始。有报道称第二次世界大战期间一些军用飞机在燃油不足时曾编队飞行，但利萨曼博士说这些未经证实。他补充道："我父亲曾是皇家空军飞行员，我的堂兄是一架在柏林上空失踪的兰开斯特轰炸机的机长。"所以他应该知道。
答案解析 (Answers & Explanations)
41. [F] False
解析：第一段末尾明确提到：“...it would not require them to buy new aircraft（这不会要求他们购买新飞机）”。题干说会促进新飞机的销售，与原文相反。
42. [T] True
解析：第二段提到：“Other birds flying in the upwash experience reduced drag (减少阻力/即题干的resistance), and spend less energy propelling themselves（花费更少的推进能量）”。题干描述完全符合原文。
43. [F] False
解析：第四段讨论乘客心理。文中说飞机距离很远，乘客可能都看不见其他飞机，但这只是为了说明感知上的安全性。文中并未说“不看见飞机”会让飞行“更加舒适（more comfortable）”，且舒适度是由于安全疑虑提出的（Would passengers feel comfortable...?）。
44. [T] True
解析：第五段首句：“It remains to be seen how weather conditions affect...（天气条件如何影响……仍有待观察）”。题干说天气的作用“尚未被清晰界定（not yet clearly defined）”，是对原文的同义替换。
45. [F] False
解析：最后一段提到有传闻说二战时军机低油量时会编队飞行，但博士说：“...but Dr. Lissaman says they are unsubstantiated（但利萨曼博士说这些传闻是未经证实的）”。题干说“It has been documented（已有记载/记录）”，与原文“未经证实”矛盾。