Airplanes are designed to withstand varying stress loads based on their intended purpose. The FAA certifies aircraft in one of three categories; normal, utility and aerobatic. The maximum load limits for each category are:
- Normal – +3.8Gs and -1.52Gs;
- Utility – +4.4Gs and -1.76Gs;
- Aerobatic – +6Gs and -3Gs.
That’s why you see warnings within the aircraft of it’s operating limitations. An aircraft flying straight and level at a constant speed is in a steady state where the aircraft’s lift is equal to its weight. Since G-force is calculated by dividing lift by weight, the load, or G-force, in this condition is equal to one (2,500 lbs. lift/2,500 lbs. weight = 1G). Exactly the same G-force as sitting in the hangar.
Resource: Plane & Pilot