Definition
The maximum load factor, expressed as a multiple of the airplane's weight, that the structure is designed to withstand without permanent deformation. Load factor is the ratio of the total aerodynamic load on the airframe to the airplane's weight, commonly expressed in Gs.
Plain English
The strongest pull the airplane is designed to take during flight without bending or being permanently damaged. If the airplane weighs 2,000 pounds and the limit load factor is 3.8 Gs, the structure is built to handle up to 7,600 pounds of total load before any permanent damage begins.
Context Anchor
Seen in aircraft limitations, maneuvering speed discussions, turbulence, steep turns, and approved maneuvers.
Derivation
Limit' meaning the boundary you must not exceed, and 'load factor' meaning the ratio of load carried by the wings to the weight of the airplane. Together: the boundary value of that ratio.
Why Pilots Care
Exceeding this value risks structural damage that can compromise the aircraft's integrity in flight.
Grounding Statement
In a hard pull-up, the airplane may feel much heavier to its own wings; the limit load factor is the certified boundary for that extra load.
Intuition Check
Do not read limit load factor as the point where the airplane is guaranteed to break. It is the maximum certified operating load; beyond it, the aircraft is outside its approved structural limit and damage may occur.
Example Sentence 1
In the normal category, this airplane has a limit load factor of 3.8 Gs, so I keep my steep turns well within that figure.
Example Sentence 2
Maneuvering speed is chosen so that an abrupt pull-up will not exceed the limit load factor.