四级复习资料大全阅读(26)_大学英语阅读

四级复习资料大全阅读(26)

　　Runways

　　Early planes were light. Early runways were sometimes just level grass fields. Paved runways became necessary when airplanes became heavier and faster. Todays big jet planes weigh hundreds of tons. They move along runways at speeds of 160 kph (100 mph).When they land, the runways take a lot of pounding and must be made of concrete or asphalt.They must have solid foundations and a surface that prevents skidding.

　　Airplanes take off into the wind in order to get better lift. They also land into the wind to have better control as they slow down. Most airports have runways pointing in different directions. This means that there are always runways on which airplanes can go into the wind as they take off and land.

　　Heavily loaded passenger jets need long runways to gather enough speed to leave the ground. Runways at some large airports are longer than 3 000m(10 000 ft).

　　At night, bright lights line the runways so that pilots can find them without trouble. A system of flashing guide lights is set up beyond the runway to help pilots land safely.

　　Control Towers

　　People who work in control towers are called air traffic controllers. They direct the movements of all planes on the ground and in the air by keeping track of them on large radar screens. Air traffic controllers tell a pilot, by radio, when and where to taxi or pilot the plane down the runway.