Airplanes disturbed from level flight and then allowed to return to level flight simply by releasing the controls can provide the pilot with a very interesting demonstration of stability. The usual result is a series of pitch oscillations below and above that of level until the airplane stabilizes in a level flight condition. This is usually true in most aircraft when combined with constant power and no changes in elevator trim. The airplane is said to possess positive dynamic stability if the oscillations gradually become smaller until level flight is achieved.
Neutral dynamic stability is displayed when the pitch oscillations do not become greater, nor do they become smaller.
Should the pitch oscillations become greater and the airplane diverges further away from level flight with each oscillation, the aircraft is said to have negative dynamic stability.