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 ]
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。