Definition
The lighter-coloured, less dense portion of a tree's annual growth ring, formed early in the growing season when growth is rapid. In aircraft wood, springwood alternates with the darker, denser summerwood to form the visible grain pattern, and the ratio and uniformity of the two are used as indicators of wood quality for structural use.
Plain English
Springwood is the pale band you see in the grain of a piece of wood. It grew quickly in spring, so it is softer and less dense than the darker bands that grew later in the year.
Context Anchor
Seen in aircraft wood structure discussions, especially when identifying wood grain, growth rings, and material condition during inspection or repair.
Derivation
Named simply for the season in which it forms. The tree grows fast in spring when water and sunlight are plentiful, producing wide, light-coloured cells. Knowing this makes the term self-explanatory when you see it in a cross-section of wood.
Why Pilots Care
On aircraft-grade wood, mechanics check the ratio of springwood to summerwood and look for uniform, closely-spaced rings. Wood with too much springwood is weaker and may not be acceptable for structural repair.
Analogy
On a cut tree stump, springwood is like the lighter band in each yearly ring, while the later-season growth is usually darker and denser.
Intuition Check
Springwood does not mean wood that acts like a spring or bends easily. It means the early-season portion of an annual growth ring.
Example Sentence 1
The technician rejected the spar blank because the wide bands of springwood indicated low density and uneven grain.
Example Sentence 2
Because springwood is softer than summerwood, it shows wear and moisture damage first during airframe inspections.