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  3. There are two main things that make aircraft engineering difficult: the need to make every component as reliable as possible and

There are two main things that make aircraft engineering difficult: the need to make every component as reliable as possible and

admin2012-07-17  32
问题     There are two main things that make aircraft engineering difficult: the need to make every component as reliable as possible and the need to build everything as light as possible. The fact that an aeroplane is up in the air and cannot stop if anything goes wrong makes it perhaps a matter of life or death that its performance is absolutely dependable.
    Given a certain power of engine, and consequently a certain fuel consumption, there is a practical limit to the total weight of aircraft that can be made to fly. Out of that weight as much as possible is wanted for fuel, radio navigational (航行的，航运的) instruments, passenger seats, or freight (货物) room, and, of course, the passengers or freight themselves. So the structure of the aircraft has to be as small and light as safety and efficiency will allow. The designer must calculate the normal load that each part will bear. This specialist is called the "stress man". He takes account of any unusual stress that may be put on the part as a precaution (预防, 预防措施) against errors in manufacture, accidental damage, etc.
    The stress man’s calculations go to the designer of the part, and he must make it as strong as the stress man says is necessary. One or two samples are always tested to prove that they are as strong as the designer intended. Each separate part is tested, then a whole assembly—for example, a complete wing, and finally the whole aeroplane. When a new type of aeroplane is being made, normally only one of the first three made will be flown. Two will be destroyed on the ground in structural tests. The third one will be tested in the air.
The two main requirements of aircraft design are______.
选项 A、ability to stay up in the air and ability to avoid breakdowns
B、making things both light and dependable
C、reliability and passenger comfort
D、speed and inexpensiveness
答案B
解析 本题问飞机设计时的两个主要要求是什么。文章第一段指出，飞机制造工程面临两个主要难题：一是要把每个部件都做得尽可能可靠，二是尽可能减轻每个部件的重量。飞机一旦到达空中，如若发生故障也不可能停下来，所以，飞机的性能要绝对可靠，这也许是个生死攸关的事情。因此，本题的正确答案应是B“飞机上的部件要重量轻且可靠性强”。
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