Definition
The concentric rings visible in the cross-section of a tree trunk, each ring representing one year of growth. In aircraft wood inspection and selection, annual rings are examined for their number per inch and uniformity, as these characteristics indicate the strength, density, and suitability of the wood for structural use in aircraft components.
Plain English
The circular bands you see when a tree is cut across the trunk. Each band is one year of the tree's growth. In aircraft work, the spacing and evenness of these bands tells you how strong and reliable the wood is.
Context Anchor
Seen in aircraft maintenance when inspecting or selecting wood used in wooden aircraft parts, repairs, or propellers.
Derivation
From Latin annus, meaning 'year.' The rings are called 'annual' because one ring forms each year as the tree grows, so counting rings tells you the tree's age and growth pattern.
Why Pilots Care
Wood density determined by ring spacing directly affects the strength of load-bearing parts; insufficient density can lead to structural failure.
Intuition Check
Annual rings are not inspection records or yearly maintenance marks. They are physical growth lines inside the wood itself.
Example Sentence 1
Before using the spruce plank for a spar repair, the mechanic counted the annual rings to confirm the wood met the minimum rings-per-inch specification.
Example Sentence 2
Closely spaced annual rings indicate slower growth and higher strength suitable for propeller construction.