Definition
A characteristic of an aircraft in which, after being disturbed from a trimmed flight condition, the resulting oscillations decrease in amplitude over time and the aircraft returns to its original state without pilot input.
Plain English
When the aircraft is bumped out of steady flight, it wobbles back and forth on its own, and each wobble gets smaller until the aircraft settles back to where it started.
Context Anchor
Seen in stability discussions when comparing how an airplane first reacts to a disturbance with how it behaves over the next several seconds.
Derivation
Dynamic comes from the Greek dynamis, meaning 'power' or 'motion.' Dynamic stability describes how the aircraft behaves over time after a disturbance — across multiple motions — rather than its immediate first reaction. Positive means the trend works in the pilot's favor: the motion fades out.
Why Pilots Care
It tells the pilot whether the airplane will naturally settle after a disturbance or whether oscillations may grow and require intervention.
Analogy
It is like rocking a chair and watching the rocking get smaller each time until the chair settles. The important point is not just that it starts back toward center, but that the motion dies out over time.
Grounding Statement
Picture the nose rising after a bump, then moving down and up in smaller amounts until the airplane settles back into steady flight.
Intuition Check
Positive does not mean “fast” or simply “good” here; it means the motion is decreasing and returning toward the original condition. Dynamic does not mean the first reaction; it means what happens over time after the disturbance.
Example Sentence 1
After a gust pitched the nose up, the aircraft's positive dynamic stability allowed the pitch oscillations to fade out without any control input from the pilot.
Example Sentence 2
During a stability demonstration the instructor noted that the aircraft’s positive dynamic stability kept the phugoid motion from growing after the student released the controls.