Definition
An oscillation in which the amplitude of each successive cycle grows larger than the one before, rather than fading away. The motion feeds on itself and worsens over time unless something is done to stop it.
Plain English
A back-and-forth motion that gets bigger and bigger instead of dying down. Each swing is wider than the last.
Context Anchor
Seen in airframe vibration, structural stability, and control-surface discussions, especially when a movement may be growing instead of damping out.
Derivation
From Latin divergere, 'to bend away from each other,' and oscillare, 'to swing.' Together: a swinging motion that bends further away from its starting point with each cycle, rather than settling back toward it.
Why Pilots Care
Divergent oscillations signal that the aircraft's natural stability is insufficient and can lead to loss of control if not corrected by design features such as dampers or stability augmentation.
Grounding Statement
Picture pushing a child on a swing and giving a slightly bigger push each time -- the swing goes higher and higher. A divergent oscillation is the aircraft version: each cycle is larger than the last.
Intuition Check
Do not read “divergent” as just “different” or “unusual.” Here it means the motion is moving away from a stable condition by getting larger.
Example Sentence 1
If the pilot over-corrects in pitch and the nose movements grow larger with each cycle, the aircraft is in a divergent oscillation.
Example Sentence 2
During preflight checks the mechanic verified that the yaw damper was serviceable to prevent divergent oscillation in flight.