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正确答案：A
(12)Which is true regarding the forces acting on an aircraft in a steady-state descent?
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A．The sum of all upward forces is less than the sum of all downward forces.
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B．The sum of all rearward forces is greater than the sum of all forces.
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C．The sum of all forward forces is equal to the sum of all rearward forces.
正确答案：C
(13)What performance is characteristic of flight at maximum L/D in a propeller-driven airplane?
? ? ?
A．Maximum range and distance glide. B．Best angle of climb． C．Maximum endurance.
正确答案：A
(14)What is the effect on total drag of an aircraft if the airspeed decreases in level flight below that speed for maximum L/D?
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A．Drag increases because of increased induced drag.
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B．Drag increases because of increased parasite drag.
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C．Drag decreases because of lower induced drag.
正确答案：A
(15)What is the relationship between induced and parasite drag when the gross weight is increased?
? ? ?
A．parasite drag increases more than induced drag B．induced drag increases more than parasite drag C．both parasite and induced drag are equally increased
正确答案：B
(16)What true airspeed and angle of attack should be used to generate the same amount of lift as altitude is increased?
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A．The same true airspeed and angle of attack B．A higher true airspeed for any given angle of attack
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C．A lower true airspeed and higher angle of attack
正确答案：B
(17)What will be the ratio between airspeed and lift if the angle of attack and other factors remain constant and airspeed is doubled? Lift will be
? ? ?
A．The same.
B．Two times greater. C．Four times greater.
正确答案：C
(18)Why is it necessary to increase back elevator pressure to maintain altitude during a turn? To compensate for the
? ?
A．loss of the vertical component of lift B．loss of the horizontal component of lift and the increase in centrifugal force
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C．rudder deflection and slight opposite aileron throughout the turn
正确答案：A
(19)At which speed will increasing the pitch attitude cause an airplane to climb?
? ? ?
A．Low speed. B．High speed. C．Any speed.
正确答案：B
(20)If no corrective action is taken by the pilot as angle of bank is increased, how is the vertical component of lift and sink rate affected?
? ? ?
A．Lift increases and the sink rate increases. B．Lift decreases and the sink rate decreases. C．Lift decreases and the sink rate increases.
正确答案：C
(21)If severe turbulence is encountered, which procedure is recommended?
? ? ?
Maintain a constant altitude. Maintain a constant attitude.
Maintain constant airspeed and altitude.
正确答案：B
【解析】遇到剧烈颠簸，如雷暴中如试图保持某一高度几乎是不可能的，而且这样做会增加机体的压力。这时应允许飞