To generate lift, a bird has merely to tilt its wings, adjusting the flow of air below and above them.
2
在气候特别湿润的年月里,平常干涸的河床下游可能会有水流动,因为地下水在那里位抬升到了地表以上。
In particularly wet years, short stretches of an otherwise dry stream-bed may have flowing water because the water table rises to intersect the land surface.
3
但是,发生了一些状况——机翼的后部并没有抬升。
But something was wrong. The ends of the wings were not lifting.