Definition
A regulatory design limit for Light-Sport Aircraft (LSA) requiring that the airplane's stalling speed in the landing configuration, with power off and at maximum certificated takeoff weight, must not exceed 45 knots calibrated airspeed (KCAS).
Plain English
To qualify as a Light-Sport Aircraft, the airplane must be designed so it cannot stall faster than 45 knots when set up to land with the engine at idle. This keeps approach and landing speeds low, which makes the airplane easier and safer to handle.
Context Anchor
Seen in light-sport aircraft eligibility and aircraft performance discussions.
Derivation
Stall speed' is the slowest speed at which the wing can still produce enough lift to support the airplane. The 45-knot figure was chosen by the FAA as a safety threshold: slower stall speeds generally mean slower landing speeds, shorter stopping distances, and reduced impact energy if something goes wrong.
Why Pilots Care
This limit keeps approach and landing speeds low enough for sport pilots to handle safely and reduces required runway length.
Intuition Check
Do not read this as a recommended speed to fly. It is a design and eligibility limit: the aircraft must not stall above 45 knots in the specified condition, but the pilot still flies with a safe margin above stall speed.
Example Sentence 1
Because the aircraft has a published stall speed of 44 knots in the landing configuration, it meets the maximum stall speed of 45 knots required for Light-Sport category.
Example Sentence 2
Before approving the model, the examiner verified it satisfied the maximum stall speed of 45 knots at maximum takeoff weight.