Definition
A simple, non-destructive inspection method used on bonded honeycomb and composite aircraft structures, in which the inspector lightly taps the surface with a coin or small metal tapper and listens to the sound produced. A clear, sharp ring indicates a sound bond between the skin and the underlying core, while a dull or flat thud suggests a void, delamination, or separation of the bond.
Plain English
Tapping a panel with a coin and listening to the sound. A bright ring means the panel is solid underneath. A dull thud means something is loose or separated inside.
Context Anchor
Seen during inspections of composite or bonded aircraft parts, especially after impact, hail, or suspected hidden damage.
Derivation
The term is literal: a coin was commonly used as the small tapping tool, and tap describes the light striking motion. The name helps because the method depends on a light tap, not a hard hit.
Why Pilots Care
Uncovers internal damage that visual checks miss, helping prevent structural failure during flight.
Analogy
Like tapping a wall to find a stud — a solid sound means something firm behind it; a hollow sound means there's a gap.
Intuition Check
Do not read coin tap as random tapping with a coin. In aviation, it means a listening check for hidden changes inside a surface.
Example Sentence 1
During the preflight, the mechanic ran a coin tap along the rudder and noted a dull spot near the trailing edge.
Example Sentence 2
After the bird strike, maintenance used coin tap across the wing leading edge to locate any delamination.