What are stability derivatives and how are they used in flight dynamics analysis?

Stability derivatives are partial derivatives of aerodynamic forces and moments with respect to motion variables and control inputs, linearized about a trim condition. Examples: CLalpha (lift change with angle of attack), Cmq (pitch moment change with pitch rate), Cnbeta (yaw moment change with sideslip). They are used in linearized equations of motion for stability analysis, eigenvalue calculation to determine modes and frequencies, transfer function development for control system design, and handling qualities assessment. Derivatives are obtained from wind tunnel tests, CFD, or flight test system identification. They vary with flight condition (Mach, altitude, configuration).