Definition
An abnormal growth pattern in softwood lumber, formed on the underside of leaning trunks or branches, characterized by dense, brittle fibers and a darker, often reddish appearance. Compression wood lacks the strength and flexibility of normal wood and is unacceptable for use in aircraft structural components.
Plain English
A flawed type of wood that grew under stress in the tree, leaving it weaker and more brittle than normal wood. It must not be used in aircraft because it can fail under load.
Context Anchor
Seen when selecting, inspecting, or rejecting wood for aircraft structural parts and repairs.
Derivation
Named for how it forms: on the side of a tree under compression (the underside of a leaning trunk or branch), where the tree lays down extra dense fibers to support the weight. The name describes the growth condition, not how the finished wood behaves under load.
Why Pilots Care
Using it in airframe repairs risks cracking, warping, and loss of structural strength under flight loads.
Intuition Check
Compression wood does not mean normal wood that is currently carrying a squeezing load. It means a growth defect already present in the wood before it is made into an aircraft part.
Example Sentence 1
During the spar inspection, the technician rejected a board after spotting the dense, reddish bands typical of compression wood.
Example Sentence 2
Repair manuals require discarding any piece containing compression wood before it is used in a load-bearing airframe component.