每日一词学英语(40): stall

失事的法航班机终于有线索了，两名男子的尸体及一些物品被发现(From Times Online, June 7, 2009: Air France search narrows after bodies found)。

失事原因呢？"Obviously the pilots did not have the right speed showing, which can lead to two bad consequences for the life of the aircraft: under-speed, which can lead to a stall, and over-speed, which can lead to the aircraft breaking up because it is approaching the speed of sound and the structure of the plane is not made for resisting such speeds," said the Minister. The high altitudes which can lead stall speed to equal the over-speed is known to jet pilots as "coffin corner". Stall speed和under-speed是近义词，stall可作名词也可作动词，日语叫“失速(しっそく)”，中文就无需我多说了，是空气动力学里的名词，含义可见Wikipedia和Wiktionary，这里援引Times Online的另一篇报道(June 4, 2009: Air France Flight 447 'may have stalled at 35,000ft')，给出通俗解释。

“A stall, in which the wings lose lift and the aircraft becomes uncontrollable,...”，“If you reduce speed too much you stall”，“...that the aircraft slowed down too much, causing a high-altitude aerodynamic stall. This would explain why the aircraft apparently broke up at altitude over the Atlantic.”在高空飞行中，飞行员无法控制飞机速度，这时飞机有可能失速也有可能超速，该法航班机是失速，造成飞机升力减小，飞机失去控制，从而从高空坠入大西洋。