Definition
A sheet metal repair in which the patch material is installed level with the surrounding skin rather than overlapping it, preserving the original aerodynamic surface. The damaged area is cut out, a doubler (reinforcing plate) is installed on the inside of the skin, and the patch is riveted in place so its outer surface sits flush with the original skin.
Plain English
A repair where the new piece of metal sits even with the surrounding surface instead of being placed on top of it, so the skin stays smooth.
Context Anchor
Seen in airframe maintenance and structural repair discussions, especially when repairing metal aircraft skin.
Derivation
Flush comes from the older English sense of being level or even with a surrounding surface. The word emphasises that the patch does not stand proud of the skin — it lies in the same plane as the surrounding metal.
Why Pilots Care
A protruding repair would disturb airflow, increase drag, and create stress points that could lead to further cracking.
Intuition Check
“Flush” does not mean washed out or cleaned here. It means level with the surrounding surface. A flush patch is not just any cover over damage; it is fitted so the outside surface remains smooth.
Example Sentence 1
The mechanic installed a flush patch on the wing skin so the repair would not disturb the airflow over the upper surface.
Example Sentence 2
Because the repair had to stay smooth, the mechanic chose a flush patch rather than an external one.