Definition
A non-magnetic aluminum housing surrounding the magnet assembly of a vertical card magnetic compass that uses electromagnetic induction (eddy currents) to slow and steady the movement of the compass card, preventing it from swinging or oscillating excessively in flight.
Plain English
A small aluminum cup around the compass magnets that quietly steadies the compass card so it doesn't keep swinging back and forth when the airplane moves.
Context Anchor
Seen in descriptions of how a vertical card magnetic compass steadies its heading indication.
Derivation
The word 'damping' comes from an old sense of 'damp' meaning to stifle or deaden — the same idea as dampening a vibrating string. Here it means slowing or calming the motion of the compass card, not making it wet.
Why Pilots Care
Without effective damping the compass card would continue swinging after turns or turbulence, delaying accurate heading information when it is most needed.
Analogy
It works like a soft brake on the compass movement. It does not stop the compass from turning; it just keeps the movement from being too jumpy.
Intuition Check
Damping does not mean making something wet here. It means reducing unwanted motion so the compass indication becomes steady.
Example Sentence 1
The aluminum-damping cup keeps the compass card steady, so the pilot can read the heading even in light turbulence.
Example Sentence 2
During preflight the instructor pointed out how the aluminum-damping cup surrounds the magnets to limit unwanted card movement.