Definition
The principal spanwise structural members of a wing, running from the fuselage toward the wingtip, designed to carry the bending and shear loads produced by lift, weight, and maneuvering forces. Spars form the main load-bearing backbone of the wing, with ribs and skin attached to them.
Plain English
Spars are the long, strong beams inside a wing that run out toward the tip and hold the wing together. They take the weight of the airplane in flight by carrying the lifting force from the wing into the fuselage.
Context Anchor
Seen in aircraft structure discussions, especially when learning how a wing is built or when reading about wing damage, repairs, or inspections.
Derivation
From Middle English 'sparre,' meaning a wooden beam or pole, the same root used for the long timbers in ship masts and roof framing. The aviation use carries the same idea: a long, strong beam doing the heavy structural work.
Why Pilots Care
Spars are the wing's primary load-carrying members. Damage to a spar — from a hard landing, ground strike, or corrosion — is a serious airworthiness issue and can ground the aircraft until inspected and repaired.
Analogy
Think of spars like the main beams in a roof or bridge. Other parts attach to them, but the main beams carry much of the load.
Intuition Check
Spars are not small surface parts of the wing. They are major internal support members that give the wing much of its strength.
Example Sentence 1
The wing's two spars carry most of the lift load from the wing into the fuselage.
Example Sentence 2
Inspectors checked the spars for cracks after the aircraft flew through severe turbulence.