Definition
A full-size drawing or template that shows a sheet metal part in its flat, unbent state, including all bend allowances and material needed before forming. The technician uses it to cut the flat blank so that, once bent to the correct angles, the finished part matches the required dimensions.
Plain English
A pattern that shows what a metal part looks like when it is laid out flat, before any bending. It tells the technician how big to cut the metal so that, once it is bent into shape, the part comes out the right size.
Context Anchor
Seen in aircraft sheet-metal repair and fabrication, especially before cutting or bending a skin patch, bracket, panel, or other metal part.
Derivation
"Flat" refers to the unbent state of the material; "pattern" comes from the Old French patron, meaning a model to be copied; "layout" is the act of marking out a design on the workpiece. Together: the marked-out shape of the part while it is still flat.
Why Pilots Care
A correct flat pattern layout helps a repaired or replacement metal part fit properly after it is formed. Poor layout can lead to a part that does not fit, has weak bends, or must be remade.
Analogy
Like unfolding a cardboard box back into its flat, original shape on the table — you can see every panel and tab before it gets folded back into a box.
Intuition Check
Do not assume the finished part is flat. Flat pattern layout means the part is planned and marked while the material is still flat, before it is bent or shaped.
Example Sentence 1
Before cutting the aluminum, the technician developed a flat pattern layout that included the correct bend allowances for each of the four angles.
Example Sentence 2
Accurate flat pattern layout prevented the finished bracket from coming out too short after all the bends were formed.