What differentiates static stability from dynamic stability?

Static stability is defined as an aircraft's initial tendency to return to its original flight condition following a small disturbance. This means that when an object is disturbed from its equilibrium position, if it tends to move back towards that position, it is statically stable. This property can be assessed by looking at the initial response of the aircraft after a disturbance, indicating how the aircraft reacts immediately following the event.

Dynamic stability, on the other hand, refers to how an aircraft behaves over time after the initial disturbance, considering factors like oscillations or movements that occur as the aircraft attempts to return to its equilibrium. Therefore, when assessing stability, static stability is specifically focused on that immediate reaction, which is why the choice describing it as related to initial tendencies after a disturbance is accurate.

The other options do not accurately capture the distinction between static and dynamic stability. For example, static stability does not necessarily involve long-term behavior, as that would pertain to dynamic stability. Furthermore, dynamic stability is not limited to helicopters; it applies to all aircraft types. Lastly, while speed can influence stability, it is not a defining characteristic of static stability. The correct choice distinctly underscores the immediate response aspect, making it integral to understanding the foundational principles of aircraft stability.