The helicopter is an incredibly versatile machine. It can fly, straight up or down, hover like a fly, and go forwards, backwards, or sideways. It therefore needs no long, prepared runway like a normal airplane does. It can operate from a flat roof in the city or from a clearing in the jungle with equal ease. However, helicopters are nowhere near as fast as normal fixed-wing airplanes and have a top speed of only about 200 miles an hour.
The helicopter has often been called the ‘flying windmill’ because of the long, rotating blades, or rotor, on top of its body. This main rotor serves as both propeller and wings to provide the thrust to drive the helicopter along and the lift to raise it off the ground. The rotor blades have the same aero-foil shapes as airplane wings and propellers to generate the required lift and thrust.
When the main rotor rotates, the body of the helicopter lends to spin by reaction in the opposite direction. To counteract this effect, a small rotor is mounted sideways on the tail. The thrust produced by this tail rotor in normal flight just balances the turning tendency of the helicopter body which therefore remains steady. Both the main and the tail rotors are driven by the helicopter engine through the same gearbox. Another way of maintaining stability in the air is to have twin main rotors which each rotate in opposite directions. Then, the “spinning” tendency of one cancels that of the other.
Movement of the helicopter in a direction—forwards, backwards, sideways, up or down—is achieved simply by varying the pitch of the rotor blades. The pitch is the angle at which the blades slice through or ‘bite’ the air. To fly straight upwards all the blades are set at the same sharp pitch. In this position they achieve maximum lift. To descend, the pitch of the blades is reduced so that the lift is insufficient to support the helicopter’s weight.
The pilot adjusts the pitch for up or down movement by moving the collective-pitch stick. This is also linked to the engine throttles so that more power is applied as the pitch increases. This is to overcome the greater air resistance with the sharper pitch. Conversely, the engine is throttled back when the pitch is reduced for descent because there is less air resistance.
To fly forwards, the pitch of the rotor blades is varied as they rotate. For forward motion, the pitch is made least at the front and gradually increased as the blade moves backwards. This has the effect of sweeping the air backwards, and therefore pushing the helicopter forwards. The same goes for any horizontal movement—the pitch is made least in the desired direction of travel. The cyclic-pitch stick controls the pitch of the rotor for horizontal flight.
1. From the first paragraph we can infer that ______.
2. What’s the basic function of the main rotor of a helicopter?
3. The movement of the helicopter in any direction is controlled by ______.
4. To fly forwards, a helicopter has to ______.
5. The word “descend” in line 4 of paragraph 4 can be best replaced by ______.
6. The phrase “This position” in line 4 of paragraph 4 refers to ______.
7. What is the most appropriate title for this passage?
问题1选项
A.nothing is perfect
B.generally speaking, helicopters are better than other airplanes
C.fixed-wing airplanes have a top speed of about 200 miles per hour
D.helicopters are not at all versatile
问题2选项
A.To counteract the spinning of a helicopter.
B.To maintain stability in the air.
C.To rotate in opposite direction.
D.To produce the force to drive it along and the lift to raise it off the ground.
问题3选项
A.a small rotor
B.its tail
C.varying the pitch of the rotor blades
D.counteracting maximum lift
问题4选项
A.support the helicopter’s weight
B.sweep the air backwards and push the helicopter forwards
C.be linked to the engine throttle
D.slice through the air
问题5选项
A.settle
B.come
C.go down
D.decrease
问题6选项
A.“To fly straight upwards”
B.“the same sharp pitch”
C.“The pitch”
D.‘‘achieve maximum lift”
问题7选项
A.The Helicopter
B.The Pitch
C.Rotating Blades
D.The flying Helicopter
第1题:A
第2题:D
第3题:C
第4题:B
第5题:C
第6题:B
第7题:A
第1题:
【选项释义】
From the first paragraph we can infer that ______. 从第一段我们可以推断出______。
A. nothing is perfect A. 没有什么是完美的
B. generally speaking, helicopters are better than other airplanes B. 一般来说，直升机比其他飞机好
C. fixed-wing airplanes have a top speed of about 200 miles per hour C. 固定翼飞机的最高速度约为每小时200英里
D. helicopters are not at all versatile D. 直升机不是多功能的
【考查点】推理判断题
【解题思路】根据第一段的内容可知，本段讲述了直升机的优点和缺点，也就是说没有什么是完美的，推知A最能概括本段。
【干扰项排除】
B、C选项，根据文中最后一句提到的：However, helicopters are nowhere near as fast as normal fixed-wing airplanes and have a top speed of only about 200 miles an hour.（然而，直升机的速度远不及普通的固定翼飞机，最高时速只有约200英里。）可知B选项属于曲解原文，C选项属于张冠李戴；
D选项，根据第一段的第一句可知属于反向干扰。
第2题:
【选项释义】
What’s the basic function of the main rotor of a helicopter? 直升机主旋翼的基本功能是什么？
A. To counteract the spinning of a helicopter. A. 抵消直升机的旋转。
B. To maintain stability in the air. B. 保持在空中的稳定性。
C. To rotate in opposite direction. C. 向相反方向旋转
D. To produce the force to drive it along and the lift to raise it off the ground. D. 产生推动直升机前进的力和使它离开地面的升力。
【考查点】事实细节题
【解题思路】根据第二段第二句：This main rotor serves as both propeller and wings to provide the thrust to drive the helicopter along and the lift to raise it off the ground.（主旋翼既充当螺旋桨又充当机翼，供推动直升机前进的推力，提供使直升机离开地面的升力。）可知D选项与原文描述一致。
【干扰项排除】
A、B、C选项根据第三段第一句：When the main rotor rotates, the body of the helicopter lends to spin by reaction in the opposite direction. To counteract this effect, a small rotor is mounted sideways on the tail. The thrust produced by this tail rotor in normal flight just balances the turning tendency of the helicopter body which therefore remains steady.（当主旋翼旋转时，直升机的机身通过反作用力向相反的方向借力旋转。为了抵消这种影响，一个被横向安装在尾部。在正常飞行中，这个尾翼产生的推力正好平衡了直升机机身的转动趋势，因此保持稳定。）可知向相反方向旋转不是主旋翼的功能，而是它的缺点，产生的力需要被尾翼抵消掉，且可以使直升机保持稳定；故A属于曲解原文、B、C选项属于张冠李戴。
第3题:
【选项释义】
The movement of the helicopter in any direction is controlled by ______. 直升机在任何方向的移动都由______控制。
A. a small rotor A. 小水平旋翼
B. its tail B. 它的尾翼
C. varying the pitch of the rotor blades C. 改变转子叶片的螺距
D. counteracting maximum lift D. 抵消最大升力
【考查点】事实细节题
【解题思路】根据第四段的第一句：Movement of the helicopter in a direction—forwards, backwards, sideways, up or down—is achieved simply by varying the pitch of the rotor blades.（直升机向前、向后、侧着、向上或向下的运动只是通过改变旋翼桨叶的螺距来实现的。）故选项C符合原文。
【干扰项排除】A、B、D选项不用于操控方向，而用于其他用处，属于张冠李戴。
第4题:
【选项释义】
To fly forwards, a helicopter has to ______. 为了向前飞行，直升机必须______。
A. support the helicopter’s weight A. 支撑直升机的重量
B. sweep the air backwards and push the helicopter forwards B. 向后扫荡空气，推动直升机向前
C. be linked to the engine throttle C. 与发动机的油门连接
D. slice through the air D. 划过空气
【考查点】事实细节题
【解题思路】根据最后一段第三句：This has the effect of sweeping the air backwards, and therefore pushing the helicopter forwards.（这有向后扫空气的效果，因此推动直升机向前。）可知选项B正确。
【干扰项排除】
A、C选项不用来使直升机操控方向，而用于其他用处，属于张冠李戴；
D选项在文中没有提及，属于无中生有。
第5题:
【选项释义】
The word “descend” in line 4 of paragraph 4 can be best replaced by ______. 第四段第四行中的“descend”一词最好用______代替。
A. settle A. 下陷，沉降
B. come B. 来
C. go down C. 下降
D. decrease D. 减少
【考查点】词汇推断题
【解题思路】根据原文句意：叶片的节距减小，使升力不足以支撑直升机的重量，这样直升机就会……可知直升机不能克服重量就会下降，所以“descend”指的是下降，故选项C正确。
【干扰项排除】
A选项尤指地面或建筑的沉降，不符合句意；
B、D选项不符合上下文语义。
第6题:
【选项释义】
The phrase “This position” in line 4 of paragraph 4 refers to ______. 第四段第四行中的“This position”指的是______。
A. “To fly straight upwards” A. “垂直向上飞”
B. “the same sharp pitch” B. “急剧的颠簸”
C. “The pitch” C. “颠簸”
D. ‘‘achieve maximum lift” D. “达到最大升力”
【考查点】推理判断题
【解题思路】根据原文句意：为了垂直向上飞行，所有的叶片都设置在相同的间距。在这个位置，他们达到最大的升力。由此可知，“this position”指的是上一句提及的相同的间距，故选项B正确。
【干扰项排除】A、C、D选项不能根据文中信息推理出来。
第7题:
【选项释义】
What is the most appropriate title for this passage? 这篇文章最合适的标题是什么？
A. The Helicopter A. 直升机
B. The Pitch B. 颠簸
C. Rotating Blades C. 旋转叶片
D. The flying Helicopter D. 飞行的直升机
【考查点】主旨大意题
【解题思路】结合全文内容可知，本文主要是讲的直升机的部件和其是如何运作的，故选项A最能概括全文。
【干扰项排除】
B选项在文中提到的范围小概括不够，不能用于总结全文；
C选项只是文章中的提到的直升机的部件，不能用于总结全文；
D选项原文并没有说是飞行中的飞机，所以不正确。
