Definition
A condition in which an aircraft, once disturbed from its trimmed flight path, develops oscillations or motions that grow larger over time rather than damping out. The aircraft moves further away from its original state with each cycle and will not return to steady flight without pilot intervention.
Plain English
If something bumps the aircraft off its path, the wobble gets bigger and bigger instead of settling down. The pilot has to step in to stop it.
Context Anchor
Seen in basic aerodynamics and aircraft stability discussions, especially when describing how an airplane responds after a gust, bump, or control input.
Derivation
‘Dynamic’ comes from the Greek dynamikos, meaning ‘relating to motion or force.’ ‘Unstable’ means ‘not steady, not returning to balance.’ Together, the term describes how an aircraft behaves over time when its motion is disturbed — not just at the first moment, but as the motion plays out.
Why Pilots Care
Dynamically unstable aircraft demand constant pilot corrections and become difficult or unsafe to fly, especially without visual references.
Grounding Statement
Picture the airplane’s nose moving slightly up after a bump, then moving up and down in larger swings instead of calming down.
Intuition Check
Dynamically unstable does not mean the airplane is instantly uncontrollable. It means the motion after a disturbance tends to grow with time unless it is corrected.
Example Sentence 1
A dynamically unstable aircraft will continue to diverge from its trimmed attitude after a gust unless the pilot intervenes.
Example Sentence 2
Production light aircraft are designed to be dynamically stable so the plane tends to return to straight flight on its own.