In air shows, you often see airplanes flying upside down. How do the wings carry an aircraft that’s turned upside down?
No matter whether an airplane is flying uninverted or upside down, the angle at which the wind meets the wing is crucial.
Almost all airplanes are capable of taking a 360-degree roll or making a loop, but not all of them can fly upside down for very long, as doing so requires a very good engine, a skilled pilot and a special wing profile. For example, if the wing is flat-bottomed with a considerable curve on the top side, the aircraft is not suited for flying upside down.
A non-inverted airplane stays aloft because the wind meets its wings at what is called the angle of attack at great speed. At this angle, the necessary lift is generated; if an aircraft is to fly upside down, the pilot must see to it that the wind meets the wings at the right angle in this position as well. The plane must also be constructed so that the supply of oil and fuel does not stop, and it must fly at a speed guaranteeing that it doesn’t stall.
link: http://www.scienceillustrated.com/technology/2011/10/how-can-airplane-fly-upside-down
link: http://www.scienceillustrated.com/technology/2011/10/how-can-airplane-fly-upside-down
