In many cases, flight testing takes place in a competitive environment to select the best airplane for accomplishing a particular mission. In this way valid comparisons can be made between airplanes that were tested on different days or at different atmospheric locations. A marble placed in the bottom of a shallow trough is said to be stable to that trim condition . When disturbed it will tend to return to that resting place at the bottom of the trough. It may overshoot and oscillate back and forth, but it will continue to seek the lowest point in the trough.
Static stability is a measure of the strength of that returning tendency.
A trough with steep sides provides a higher level of static stability for the marble than one with shallow sides. If we set the marble on a flat table, there is no tendency for it to return to any trim point . If we turn the trough upside down, we can balance the marble at one point on the top of the trough, but when disturbed it will tend to move away from the balance point at an increasing rate. Damping Damping is resistance to motion. Damping only exists when actual movement is occurring.