Plain English Meaning
Rivets that sit flat with the surface of the aircraft instead of sticking out, so the skin stays smooth and air flows over it more cleanly.
Full Definition
Rivets installed so that their heads sit level with the surrounding aircraft skin rather than protruding above it. The skin is countersunk or dimpled to receive a tapered rivet head, producing a smooth outer surface that reduces skin friction drag.
Context Anchor
Seen in aircraft construction and aerodynamics discussions, especially when explaining how surface smoothness affects skin friction drag.
Derivation
‘Flush’ here means level with a surrounding surface — the same sense as a flush door or flush-fitted panel. It signals that nothing protrudes above the skin.
Why Pilots Care
They reduce surface irregularities that increase drag, improving and .