填空题

Using a new (36) device called Microwave Landing System (MLS) , airplanes will be able to land themselves. With MLS, more planes will be able to land on the ground more quickly and more safely without a pilot’s touching the controls. From the time a plane enters the zone of area covered by MLS until it lands, it is controlled com plctcly and (37) Bad weather has no effect on the system, even zero (38) fog. The normal operations for landing—engine reversal, (39) , and steering—are (40) by MIS. The pilot does not have to do anything; however, the pilot may take control again if the need (41) Using the current (42) Landing System(ILS) ,pilots follow a radio beam. The ILS beam is very narrow, like a long tube. To follow it, airplanes must fly (43) along the beam, starting at least eight kilometers from beginning their approach to touchdown. In many cases, pilot must begin to follow ILS beam as far as 24 kilometers away from a touchdown point at the airport. (44) . The MLS uses a high-frequency beam, shaped like a big funnel with a large mouth. (45) instead of having to follow the long, narrow, straight in approaches of ILS. The MLS is so precise that planes can come in on parallel runways at intervals as short as 40 seconds apart without danger of collision. (46)