Choose the best alternative to fill the gaps in these sentences.

1. The aircraft rises into the air and keeps there because of ______.

a) wind b) light weight c) forces working on it

2. The air traveling across the top of the wing creates a _______ on the upper surface.

a) increased pressure b) reduced pressure c) reduced lift

3. Aircraft high speed is produced by a _______ that acts in the direction of airplane’s motion.

a) force of thrust b) wing c) flight controls

4. _____ and _____ are artificially created forces.

a) lift, drag b) thrust, lift c) thrust, gravity

5) The engine-propeller combination is designed ______ .

a) to create lift b) to overcome drag c) to decrease weight

Focus on Writing

Translate the text in a written form.

High-Speed Flight Ranges

Transonic. When the speed of flight is less than the speed of sound, but of sufficient velocity to induce supersonic airflow over some part of the structure of the aircraft, the airplane is said to be in the transonic speed range. That is, it is in the region of speed of sound.

Supersonic.As flight speed increases further, a point is reached where the airflow over all parts of the aircraft is supersonic, or above the speed of sound. When this happens, the airplane is in the supersonic speed range.

Hypersonic.As a body moves through the air at high speeds, a short amount of time is required for the molecules of air to adjust themselves to the presence of the fast-moving body and to readjust themselves after the body has passed through them. This period of adjustment and readjustment is called the relaxation time. If a body is moving at a speed greater that the relaxation time, it can be classed as being in the hypersonic speed range.

UNIT 5

Wing

Preparing to Read

<== попередня сторінка	\|	наступна сторінка ==>
Agreeing Disagreeing	\|	Brainstorm all possible terms related to the topic.

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