聽音頻：

  　如不能正常播放，點擊此處下載聽力mp3>>>

  　進入專題：2015年聽力風暴來襲，英語四級每日一聽！

　　While flying high above Earth's surface, jet fighter pilots may suffer loss of eyesight for brief periods. Some pilots may even lose consciousness -- not being able to recognize what is happening around them. These experiences, commonly called blackouts, can lead to tragic results.

　　Now, an Israeli company says it has developed a device that could save pilots' lives at such times.

　　Yaron Kranz is senior research and development director at Elbit Systems. He is also a retired fighter pilot. He says two different situations can lead to a pilot's loss of consciousness.

　　"One is ‘G-LOC' or G Loss of Consciousness, and the other one is hypoxia, which is lack of oxygen to the brain."

　　G-LOC happens when the airplane is making a sharp turn or speeding up very quickly. During these periods, centrifugal force reduces the normal flow of blood to the pilot's brain. At high speeds, loss of control of the aircraft has proved deadly for many pilots.

　　Hypoxia, or lack of oxygen, can affect anyone at extreme heights. That is why passenger planes are equipped with oxygen masks. Passengers are always told before flying to put on the masks in case of a sudden loss of air pressure.

　　Current devices for preventing such dangerous situations are very large. So Elbit Systems and a small start-up company, called LifeBEAM, developed a system they are calling Canary. It uses small, non-invasive sensing equipment. Yaron Kranz says the sensors are built into the helmet worn by the pilot.

　　"The pilot doesn't have to do anything in order to activate those sensors and they are small enough and wise enough to give the information to gather the physiological data that is required."

　　By physiological data, he means information related to the processes and activities that keep the person alive. When the danger is real, the system sends a message to the visor on the front of the helmet. If it senses that the pilot has lost consciousness, it tells the plane's computer to activate the autopilot. The autopilot will then take control of the plane's movement until the pilot wakes up.

　　Elbit Systems is now developing its Canary device for U.S. F-35 fighter jets and other aircraft.

　　I'm Jonathan Evans.

　　VOA's George Putic reported on this story from Washington. George Grow adapted it for Learning English. Mario Ritter was the editor.