Definition
A condition in which the smooth flow of air over a wing or other surface breaks away from that surface instead of following its contour. Once the airflow separates, it becomes turbulent and disorganized, and the surface loses much of the lift or control authority it would normally produce.
Plain English
The air stops hugging the surface and breaks away into a messy, churning flow. When that happens, the wing or tail can no longer do its job properly.
Context Anchor
Seen in discussions of stalls, high nose-up attitudes, and T-tail airplanes, where disturbed air from the wing can affect the tail.
Derivation
‘Separated’ comes from the Latin separare, meaning ‘to set apart.’ The airflow literally sets itself apart from the surface it had been following.
Why Pilots Care
It marks the beginning of a stall, demanding prompt recovery action to reattach the flow and regain control.
Grounding Statement
Picture water flowing smoothly over a curved rock, then suddenly tumbling off into froth — that switch from smooth to chaotic is what happens to the air over a wing when it separates.
Intuition Check
Separated does not mean the air has simply split into two clean paths. Here it means the smooth flow has let go of the aircraft surface and become disturbed.
Example Sentence 1
As the angle of attack increased past the critical point, the airflow separated from the upper surface of the wing and the aircraft stalled.
Example Sentence 2
Buffeting warned of separated airflow developing on the T-tail aircraft at a lower angle than expected.