Definition
A repeating back-and-forth motion that continues at the same amplitude over time, with no reduction in size from one cycle to the next. In aircraft dynamics, it describes a disturbance that, once started, keeps oscillating at a constant magnitude rather than dying out.
Plain English
A motion that keeps swinging back and forth without getting smaller. It does not settle down on its own.
Context Anchor
Seen in aircraft structure, control system, and vibration discussions when describing motion that does not die out on its own.
Derivation
From the prefix 'un-' meaning 'not', and 'damped', from Middle Dutch 'dampen' meaning 'to deaden' or 'to suppress'. So 'undamped' literally means 'not deadened' -- the motion is not being suppressed or reduced.
Why Pilots Care
Undamped oscillations can signal structural problems such as flutter that lead to fatigue or failure if left unresolved.
Analogy
Imagine pushing a child on a swing once and walking away. If the swing keeps going at the same height forever, that is undamped. In real life, friction and air resistance slowly shrink the swing -- that is damping.
Grounding Statement
Picture a surface or part moving left-right-left-right over and over without the motion getting smaller.
Intuition Check
Undamped does not mean “not wet.” Here it means the motion is not being reduced or slowed by a damping force.
Example Sentence 1
The technician noted an undamped oscillation in the control surface during the ground test, indicating the damper was not functioning.
Example Sentence 2
High-speed flight revealed undamped oscillation in the elevator controls.