Definition
A non-magnetic metal disk, typically aluminum, mounted on a rotating shaft inside certain flight instruments and positioned within the field of a permanent magnet. As the disk rotates, the magnet induces eddy currents in it, and those currents create a drag force that opposes the motion. This drag smooths out rapid fluctuations in the instrument's reading without affecting its steady-state response.
Plain English
A small metal disk inside an instrument that quietly slows down jittery movements so the needle reads smoothly instead of bouncing around.
Context Anchor
Seen in flight instrument discussions about eddy current damping, where instruments need a needle or card to move smoothly and then stop without bouncing.
Derivation
Damping comes from an old word meaning to deaden or muffle, the same root as damping down a fire. Disk simply describes the shape. Together they describe a flat plate whose job is to muffle unwanted motion.
Why Pilots Care
Steady instrument indications reduce pilot workload and help prevent over-corrections during instrument flight.
Analogy
It is like gently putting your hand near a swinging door to slow it down, except the damping disk does the slowing magnetically, without touching another part.
Intuition Check
Do not read “damping” as making something wet. Here, damping means reducing unwanted swinging or bouncing in an instrument indication.
Example Sentence 1
The damping disk in the vertical speed indicator keeps the needle from jumping around in light turbulence.
Example Sentence 2
During preflight checks, the instructor pointed out how the damping disk prevents the rate-of-turn needle from oscillating.