Aircraft stability

Aircraft stability is an aircraft’s tendency to return toward, or remain in, a balanced flight condition after a disturbance. It includes static responses immediately after disturbance and dynamic behavior over time.

Static stability: The initial tendency of a system to move back toward equilibrium after a small disturbance. It describes the aircraft’s immediate response before its motion over time is considered.
Aircraft flight control surfaces: Movable aircraft surfaces that change aerodynamic forces and moments to control flight. They can alter stability as well as command changes in aircraft attitude.
Aircraft design: The engineering process of defining and shaping an aircraft to meet performance, safety, and operational requirements. Stability requirements influence configuration, mass distribution, and aerodynamic layout.
Aircraft controllability: An aircraft’s ability to respond to control inputs and achieve commanded changes in flight. An aircraft can be stable yet difficult to maneuver, or unstable yet controllable with active systems.
Dynamic stability: The tendency of a system’s motion to decay, persist, or grow after a disturbance. It distinguishes a momentarily restoring response from one that settles into balanced flight.
Angle of attack: The angle between an airfoil’s reference line and the oncoming airflow. Changes in angle of attack commonly trigger the aerodynamic forces involved in pitch stability.
Relaxed stability: An aircraft design with weak or negative natural stability, relying on active control to maintain desired flight behavior. Modern fighters may trade natural stability for maneuverability using continuous computer control.
Aircraft handling qualities: The characteristics of an aircraft’s response as experienced by pilots during control and maneuvering. Handling qualities include stability but also depend on control sensitivity and pilot workload.
Center of gravity: The point at which an object's weight can be considered to act. Its position relative to the aerodynamic center strongly affects longitudinal stability.
Longitudinal stability: An aircraft’s stability in pitch about its lateral axis. It is the stability mode most directly tied to angle of attack and pitching moment.

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