Definition
A length of structural steel rolled into a U-shaped cross section, with a flat back (the web) and two parallel sides (the flanges) at right angles to it. Channel iron is used as a structural member where stiffness and resistance to bending are needed in one direction more than another.
Plain English
A piece of steel shaped like a squared-off letter U when you look at the end of it. The flat part gives it strength, and the two sides keep it from twisting or bending easily.
Context Anchor
Seen in aircraft maintenance, shop fabrication, repair drawings, and descriptions of metal supports or frames.
Derivation
Called 'channel' because the U-shape forms an open trough or channel along its length. 'Iron' is a traditional shop term for structural steel shapes, carried over from older construction language even though the material today is usually steel rather than pure iron.
Why Pilots Care
These members carry flight loads and maintain airframe shape; damage or corrosion can affect structural integrity.
Intuition Check
Channel iron is not a radio channel, and it is not a household iron. Here, “channel” means the U-shaped form of the metal, and “iron” means the metal material.
Example Sentence 1
The engine overhaul stand was welded up from lengths of channel iron to handle the weight of the powerplant.
Example Sentence 2
Channel iron was riveted between the frames to stiffen the cockpit floor.