Definition
A structural beam supported rigidly at one end only, with the other end projecting freely. The fixed end carries all of the bending loads and shear forces produced by the unsupported portion.
Plain English
A beam held firmly at one end and sticking out into open space at the other, with no support under the far end.
Context Anchor
Seen in aircraft structure discussions, especially when describing cantilever wings and the internal supports that carry wing loads.
Derivation
From 'cantilever,' an old building term for a bracket projecting from a wall to support something above it (like a balcony). The word likely comes from 'cant' (a slanted brace) plus 'lever.' The aviation use carries the same idea: support at one end, free at the other.
Why Pilots Care
Enables lighter, stronger wings without struts or wires, improving performance and reducing drag.
Analogy
Think of a diving board. It is bolted to the pool deck at one end and the other end hangs out over the water with nothing under it. All the weight of the diver is carried by the fixed end.
Intuition Check
Do not think of “beam” as a beam of light here. In aircraft structures, a beam is a strong load-carrying piece, and “cantilever” means it is supported from one end rather than held up along its length.
Example Sentence 1
The aircraft uses a cantilever wing design, so there are no external struts between the fuselage and the wingtip.
Example Sentence 2
Inspectors examined the cantilever beam attachment points for cracks after the hard landing.