stability of an airplane
The aircraft's response to disturbance is associated with the inherent degree of stability built in by the designer, in each of the three axes; and eventuating without any reaction from the pilot. Another condition affecting flight is the aircraft's state oftrim – or equilibrium where the net sum of all forces equals zero. Some aircraft can be trimmed by the pilot to fly 'hands off' for straight and level flight, for climb or for descent. If the trim is wrong, and perhaps it flies with one wing low, inherent stability will maintain that wing-low attitude and not restore the aircraft to a wings-level attitude. It is desirable that longitudinal trim doesn't change significantly with alterations in power, nor does directional trim change significantly with alterations in airspeed.
