What term describes the initial tendency to return to equilibrium after a disturbance in the longitudinal axis?

• A. Static stability
• B. Dynamic stability
• C. Neutral stability
• D. Lateral stability

Answer: (A)

Static stability describes the initial tendency of an aircraft to return to its original pitch attitude after a disturbance about the longitudinal axis. If the airplane has positive static stability, a small nose-up or nose-down displacement produces restoring moments that push the nose back toward trim right away. This immediate restoring tendency is what static stability captures. Dynamic stability, on the other hand, looks at how the motion evolves over time after that initial response—whether it settles smoothly, oscillates, or grows. Neutral stability means there’s no initial tendency to return or diverge—the new attitude remains. Lateral stability involves roll about the longitudinal axis and is not describing the initial pitch response.