Definition
The earliest stage of a stall, where the wing's angle of attack has reached the point at which airflow is just beginning to separate from the upper surface, but full aerodynamic stall has not yet developed. At this stage the pilot will typically feel buffet, hear the stall warning horn, and notice a loss of control effectiveness, and recovery can be achieved by promptly reducing the angle of attack before a full stall occurs.
Plain English
The very start of a stall — the warning stage, just before the wing actually stops flying. The aircraft is telling you it's about to stall, and a quick reduction of back pressure on the controls will prevent it.
Context Anchor
Seen in stall training, aircraft handling discussions, and explanations of how different wing shapes begin to lose lift.
Derivation
From Latin 'incipere', meaning 'to begin'. An incipient stall is a stall that is just beginning — caught at the onset rather than allowed to fully develop.
Why Pilots Care
Recovery is easiest and requires the least altitude loss when the stall is still incipient.
Grounding Statement
Picture the first moment the smooth airflow over the wing starts to break away; that is the incipient stall stage.
Intuition Check
A stall here does not mean the engine has stopped. It means the wing is no longer producing lift normally because the airflow over it is breaking down.
Example Sentence 1
When the stall warning horn sounded during the steep turn, the pilot recognized the incipient stall and immediately lowered the nose to recover.
Example Sentence 2
In the training maneuver the airplane entered an incipient stall at a higher angle of attack than expected due to its wing planform.