Definition
Slang term used in sheet metal aircraft structures work for the small circular marks or impressions left on a metal skin around a rivet, typically caused by an improperly used rivet set or bucking bar slipping during the riveting process. Ringworms are a cosmetic and quality defect indicating poor riveting technique.
Plain English
Round scuff marks left on an aircraft's metal skin around a rivet when the riveting tool slips or is held wrong. They show the riveting wasn't done cleanly.
Context Anchor
Seen during inspection or maintenance of aircraft finishes, especially on fabric-covered aircraft.
Derivation
Named for the visual resemblance to the circular skin lesion called ringworm. The mark is a ring-shaped impression around the rivet head, so mechanics borrowed the everyday word for a familiar ring-shaped pattern.
Why Pilots Care
Left unaddressed, these patterns can progress into cracks that compromise structural integrity and lead to in-flight failure.
Intuition Check
Ringworms are not worms and not a medical condition here. In this context, they are ring-shaped defects in an aircraft finish.
Example Sentence 1
The inspector flagged several ringworms on the wing skin and asked the mechanic to review his rivet set technique.
Example Sentence 2
The bearing race showed early ringworms, prompting replacement before the next annual.