Definition
A structural member designed to resist forces pushing inward along its length, holding two points apart against compressive loads. In aircraft structures, compression struts are commonly found in wing trusses and landing gear assemblies, where they maintain spacing between spars or other components and carry loads that try to squeeze them shorter.
Plain English
A stiff bar or tube placed between two parts to keep them from being pushed together. It holds things apart when something is trying to squash them closer.
Context Anchor
Seen in airframe structure inspection and repair, especially inside wings and other braced aircraft structures.
Derivation
Compression' comes from Latin 'comprimere' meaning 'to press together.' 'Strut' comes from Old English 'strutian' meaning 'to stand stiffly.' Together: a stiff member that resists being pressed together.
Why Pilots Care
In a wing, compression struts help maintain the structural shape under flight loads. If one fails or is damaged, the wing's load path is compromised — which is why mechanics inspect them carefully and pilots should understand what they're looking at during a structural walkaround.
Analogy
Think of the crossbar in a folding chair that keeps the two legs from collapsing inward when you sit down. It's not pulling anything — it's pushing back to hold the spacing.
Intuition Check
Do not think of a compression strut as any aircraft strut that happens to be under the airplane. Here, “compression” means the member is designed to resist being squeezed along its length.
Example Sentence 1
During the wing inspection, the mechanic checked the compression strut between the front and rear spars for any signs of bending or cracking.
Example Sentence 2
Wing compression struts transfer loads between the upper and lower spars during flight.