Definition
A lengthwise crack or split in a piece of wood that runs across the annual growth rings, usually caused by uneven shrinkage as the wood dries. In aircraft structures, a check is considered a defect that can weaken the wood and may render it unsuitable for use in load-bearing components such as spars, ribs, or formers.
Plain English
A small crack along the grain of a piece of wood, usually caused by drying. In aircraft work, it counts as damage and can mean the wood is not safe to use.
Context Anchor
Seen during inspection and repair of wooden aircraft structures, such as spars, ribs, plywood skin, and wooden propellers.
Derivation
From the Old French 'eschec', meaning a stop or obstacle. In woodworking the term came to describe a flaw that 'stops' the wood from being sound — a break in its continuity.
Why Pilots Care
Checks reduce structural strength and can propagate under flight loads, leading to failure if left unrepaired.
Intuition Check
Do not read “check” here as “inspect” or “verify.” In this context, a check is the defect itself: a crack or split in wood.
Example Sentence 1
During the wing inspection, the mechanic rejected the spruce plank because a deep check ran along its length.
Example Sentence 2
Small surface checks in non-critical wood parts may be acceptable if they do not exceed limits in the maintenance manual.