Definition
The minimum airspeed at which an airplane can sustain level, unaccelerated flight while supporting exactly its own weight (a load factor of 1G) before the wing exceeds its critical angle of attack and stalls.
Plain English
The slowest speed at which the wings can still hold the airplane up in straight, level flight without stalling, when the airplane is only carrying its own weight and nothing extra is pushing it down into its wings.
Context Anchor
Seen in angle-of-attack discussions, stall training, airplane performance data, and explanations of why stall speed increases during maneuvering flight.
Derivation
The '1G' refers to one unit of gravitational load — the airplane's normal weight in straight-and-level flight. 'Stall' comes from the old sense of an engine or motion 'stalling,' meaning coming to a stop; here it refers to the wing losing lift, not the engine quitting.
Why Pilots Care
It is the baseline stall speed from which all maneuvering stall speeds are calculated as load factor increases.
Grounding Statement
At 1G, the wing is only supporting the airplane’s normal weight; when maneuvering adds more G, the wing must work harder and reaches the stall sooner.
Intuition Check
Do not read 1G stall speed as “the speed where this airplane always stalls.” It means the stall speed only under normal 1G loading; added G raises the stall speed.
Example Sentence 1
The published 1G stall speed gives the pilot a baseline, but in a 60-degree banked turn the airplane will stall at a noticeably higher airspeed.
Example Sentence 2
In steady level flight with no turns or pitch changes, the airplane stalls at its 1G stall speed.