Static stability is the initial tendency an aircraft displays when disturbed from a state of equilibrium.

• A. The initial tendency an aircraft displays when disturbed from a state of equilibrium.
• B. The aerodynamic pitching moments to return to equilibrium.
• C. The dynamic pressure of air.
• D. The rate of change of airspeed.

Answer: (A)

Static stability is about the immediate response of an aircraft to a small disturbance from its trimmed, equilibrium state. When the aircraft is nudged, a statically stable configuration produces a restoring pitching moment that tends to bring the aircraft back toward its original attitude. So the statement that matches this concept is the one describing the initial tendency of the aircraft after disturbance. The mention of restoring pitching moments explains the mechanism behind that tendency, but the definition of static stability itself is about the initial response. Dynamic pressure and rate of change of airspeed are not about how the attitude responds to a disturbance, so they don’t define static stability.