题目：How Can Air Traffic Controllers Lose a Plane?
From Learning English, this is In the News.
The search for a Malaysia Airlines passenger jet expanded this week. The airplane, a Boeing 777, disappeared last Saturday on a flight from Kuala Lumpur to Beijing. It was carrying 239 people. At first, the search was along its expected flight path. But by weeks end, crews had expanded the search across parts of southern Asia for any evidence of Malaysian Airlines Flight 370.
With satellites and other technology available, how can a plane as large as the Triple-7 just disappear? Air safety expert John McGraw says it is easier than you may think.
People are under the impression that every airplane, even when its flying across the ocean, is observed on some kind of radar scope, with a human being looking at that scope. And its just not the case. Radars dont reach that far.
But John McGraw says there are also a lot of devices inside the Triple-7 that can help searchers follow its movement. Systems in the aircraft send altitude, weather conditions, position and speed to air traffic controllers. There are also at least three ways the pilots can communicate with controllers. Another tool is the flight data recorder or black box. If the plane is downed in the ocean, the black box sends out a signal that can travel up to three kilometers away.
Many people remember when a French passenger jet disappeared five years ago. Air France Flight 447 went missing as it flew from Brazil to Paris. Its wreckage was eventually found in the Atlantic Ocean.
Air safety expert John McGraw remembers the National Transportation Safety Board taking action after the French jet went missing. He says US officials called for continuous download of an aircrafts flight data recorder information in case of emergencies.
In the past they havent been able to justify installing that kind of equipment, because its expensive, and because there hadnt been that many accidents where it would have come into play. This will certainly provide some additional motivation and there may be calls to do that.
Malaysia Airlines Flight 370 was last seen on radar above Vietnam and Malaysia. Air traffic controllers in both countries say they did not receive any message that the plane may have been in trouble. On Tuesday, Malaysian media reported that the Malaysian military had noted the aircraft flying toward the countrys west coast. That is far from where controllers lost contact with the plane.
The next day, China released satellite images showing three large objects floating in waters between Malaysia and Vietnam. But China later said it could not confirm the objects belonged to the missing aircraft.
The Wall Street Journal reported that the plane could have stayed in the air for several hours past the time of its last confirmed location. The newspaper later said that the plane continued to send information about its engines and performance to satellites for five more hours. That suggests Flight 370 could have remained in the air or was on the ground somewhere. Why the signals stopped is unclear.
This is a developing story. For the latest news on the Malaysian airliner, go to 51.com.
And thats In the News from Learning English. Im Steve Ember.