Definition
A condition in which an aircraft, after being disturbed from equilibrium, oscillates with an amplitude that neither grows nor decays over time. The oscillations continue at a constant size indefinitely until acted on by an outside force.
Plain English
When the airplane gets bumped out of its steady flight, it starts rocking back and forth, and those rocks stay the same size — they don't get bigger and they don't fade away.
Context Anchor
Seen in aircraft stability discussions, especially when comparing how an airplane behaves after a gust, control input, or other disturbance.
Derivation
Dynamic comes from the Greek 'dynamis' meaning power or motion — it refers to behavior over time. Neutral means 'neither one way nor the other.' Together: motion over time that neither builds up nor dies down.
Why Pilots Care
The aircraft will not return to straight-and-level flight on its own and requires pilot input to stop the constant oscillations.
Analogy
It is like a swing that keeps moving back and forth to the same height. It is not slowing down, but it is also not swinging higher and higher.
Grounding Statement
Picture a swing that's been pushed once: if it keeps swinging the same height forever without slowing down, that's neutral dynamic stability.
Intuition Check
Neutral does not mean “no motion.” Here, neutral means the motion continues without getting smaller or larger.
Example Sentence 1
An aircraft with neutral dynamic stability will continue to oscillate at the same amplitude after a disturbance until the pilot intervenes.
Example Sentence 2
During the stability demonstration the instructor noted neutral dynamic stability because each cycle returned to the same bank angle without damping.