Definition
A high-lift system in which high-pressure air, usually bled from the engine compressor, is ducted to small slots on the upper surface of a wing or flap and blown over it at high velocity. This energizes the boundary layer — the thin layer of slow-moving air clinging to the wing — preventing it from separating at high angles of attack and allowing the wing to keep producing lift at much lower airspeeds than it otherwise could.
Plain English
A system that pipes fast-moving air from the engine and blows it over the top of the wing or flap. This keeps the airflow stuck to the wing surface at slow speeds, so the wing keeps producing lift instead of stalling.
Context Anchor
Seen in discussions of high-lift systems, special wing designs, and airplanes that use engine or compressor air to improve low-speed lift.
Derivation
‘Boundary layer’ is the thin film of air right against the wing surface that moves more slowly than the free airstream because it is dragged on by the surface. ‘Blown’ refers to actively forcing high-energy air into that layer to keep it moving and attached. ‘Control’ means managing whether that layer stays attached or separates.
Why Pilots Care
It permits shorter takeoff and landing distances and improves low-speed handling without enlarging the wing.
Analogy
It is like using a fan to keep smoke flowing smoothly along a curved surface instead of letting it break away from the surface too soon.
Grounding Statement
Picture air being blown across the top of a wing to help the natural airflow stay smooth and attached instead of peeling away.
Intuition Check
“Blown” does not mean damaged, burst, or failed here. It means air is intentionally directed over the wing surface to improve airflow.
Example Sentence 1
The aircraft’s blown boundary layer control system allowed it to maintain lift during steep, low-speed approaches to short carrier decks.
Example Sentence 2
Pre-flight checks include verifying that the bleed-air lines feeding the boundary-layer slots are free of obstructions.