Definition
A formed sheet metal structural section whose cross-section resembles a top hat: a flat top, two vertical sides, and two outward-turned flanges at the base. The flanges allow the channel to be riveted, bonded, or fastened to a flat sheet, where it acts as a stiffener that increases the sheet's resistance to bending and buckling.
Plain English
A long strip of metal bent into the shape of a top hat when viewed from the end. The wide bottom edges sit flat against a piece of sheet metal so it can be riveted on to make that sheet stronger and stiffer.
Context Anchor
Seen in aircraft structure descriptions, sheet-metal repair, inspection notes, and structural drawings.
Derivation
Named for its cross-sectional shape: the profile looks like a man's top hat sitting on a brim. The 'crown' is the flat top, the 'sides' are the walls, and the 'brim' is the outward flanges that fasten to the underlying sheet.
Why Pilots Care
Pilots and especially aircraft owners or A&P students encounter hat channels during inspections and repairs. Recognising the part by name helps when reading structural repair manuals and discussing damage or corrosion in stiffened panels.
Analogy
A flat piece of paper bends easily, but if you fold a raised ridge into it, it becomes much harder to bend. A hat channel does a similar job for thin aircraft metal.
Intuition Check
Do not read “hat channel” as a clothing item or a radio channel. Here it means a shaped metal reinforcing piece in the aircraft structure.
Example Sentence 1
The mechanic riveted a new hat channel along the underside of the floor panel to restore its stiffness after the corrosion repair.
Example Sentence 2
During the inspection, cracks were found where the hat channel attached to the bulkhead.