Definition
A soft metal sealing ring, typically made of copper or annealed aluminum, designed to deform permanently when compressed between two mating surfaces to form a leak-proof seal. Crush gaskets are single-use and must be replaced each time the joint is opened.
Plain English
A soft metal washer that gets squashed flat when you tighten a fitting, filling in any tiny gaps to stop leaks. Once it's been crushed, it can't be reused.
Context Anchor
Seen during aircraft maintenance on items such as spark plugs, drain plugs, and fluid connections where a tight seal is needed.
Derivation
Named for what it does: it is crushed during installation. The deformation is the seal -- the soft metal flows into surface imperfections that a rigid washer could not fill.
Why Pilots Care
A properly crushed gasket prevents dangerous fuel or oil leaks that could lead to fire or engine failure.
Analogy
It is like a soft washer that makes its own custom fit when squeezed between two hard surfaces.
Intuition Check
A crush gasket is not a gasket that has been accidentally damaged. It is made to be crushed slightly as part of how it seals.
Example Sentence 1
After draining the oil, he installed a new crush gasket on the drain plug before torquing it down.
Example Sentence 2
After removing the oil cooler for inspection, always install a fresh crush gasket to restore the seal.