Definition
A stress in a structural member caused by a load applied across its length, producing tension on one side of the member and compression on the opposite side. The fibers on the convex (outer) side are stretched while the fibers on the concave (inner) side are squeezed.
Plain English
The strain placed on a part when a force tries to bend it. One side gets stretched and the other side gets squashed at the same time.
Context Anchor
Seen in aircraft structures and maintenance discussions, especially with wings, spars, struts, landing gear parts, and other pieces that must carry loads without bending too much or cracking.
Derivation
From the Old English 'bendan' (to bend, to curve) combined with 'stress,' from the Latin 'strictus' meaning drawn tight. Together it literally means 'the tightness produced by bending,' which captures exactly what is happening inside the material.
Why Pilots Care
Excessive bending stress can cause permanent deformation or structural failure in wings and other primary structure, directly affecting airworthiness and safety margins.
Analogy
If you bend a ruler, the outside of the curve stretches while the inside of the curve squeezes together. An aircraft part under bending stress is doing the same thing, but the loads may be much larger.
Grounding Statement
Picture pressing down on the middle of a ruler held at both ends. The bottom face stretches, the top face compresses, and that combined strain is bending stress.
Intuition Check
Stress here does not mean worry or nervousness. It means force inside a material as that material resists being bent.
Example Sentence 1
In flight, the wing spar carries large bending stress as lift pushes the wings up while the weight of the fuselage pulls down at the center.
Example Sentence 2
Maintenance inspectors check for cracks that can start where repeated bending stress has fatigued the metal.