Why does the aircraft stall when it loses airspeed ?

[rapidshot]

to my opinion the best explanation is hidden in the definition of the neutral point and the static margin




Neutral point


A mathematical analysis of the longitudinal static stability of a complete aircraft (including horizontal stabilizer) yields the position of center of gravity at which stability is neutral. This position is called the neutral point. (The larger the area of the horizontal stabilizer, and the greater the moment arm of the horizontal stabilizer about the aerodynamic center, the further aft is the neutral point.)

The static center of gravity margin (c.g. margin) or static margin is the distance between the center of gravity (or mass) and the neutral point. It is usually quoted as a percentage of the MAC . The center of gravity must lie ahead of the neutral point for positive stability (negative static margin). If the center of gravity is behind the neutral point, the aircraft is longitudinally unstable (the static margin is positive), and active inputs to the control surfaces are required to maintain stable flight. Ultimately, the position of the center of gravity relative to the neutral point determines the stability, control forces, and controllability of the vehicleLongitudinal static stability

Longitudinal static stability is important in determining whether an aircraft will be able to fly as intended. - Static stability :As any vehicle moves it will be subjected to minor changes in the forces that act on it, and in its speed....

Static margin
Static margin is a concept used to characterize the static stability and controllability of aircraft and missiles.*In aircraft analysis, static margin is defined as the distance between the center of gravity and the neutral point of the aircraft....




Pitching Moment Curves

If we are given a plot of pitching moment vs. CL or angle of attack, we can say a great deal about the airplane's characteristics.