1. Load factor is the ratio between the total airload imposed on the wing in flight and the gross weight of the airplane.
a. The amount of excess load that can be imposed on an airplane’s wings varies directly with the airplane’s speed and the excess lift available.
1. At low speeds, little excess lift is available, so little excess load can be imposed.
2. At high speeds, the wings’ lifting capacity is so great that the load factor can quickly exceed safety limits.
b. An increased load factor will cause an airplane to stall at a higher airspeed.
c. As bank angle increases, the load factor increases. The wings not only must carry the airplane’s weight but also must bear the load imposed by the centrifugal force.
1. The determinant of load factor in level, coordinated turns is the amount of bank.
2. A change of airspeed does not affect load factor given a constant angle of bank, although it does directly affect the rate and radius of turn.
2. Load factor (or G units) is a multiple of the regular weight or, alternatively, a multiple of the force of gravity.
a. Unaccelerated straight flight has a load factor of 1.0 (by definition).
b. A 60° level bank has a load factor of 2.0. Thus, a 3,000-lb. airplane in a 60° bank would require the wings to provide lift for 6,000 pounds.
c. The best indication of positive (+) or negative (–) Gs is the change in how heavy (positive) or light (negative) you feel in your seat.
3. Maximum safe load factors (limit load factors):
a. The limit load factor is the ratio of maximum sustainable load imposed on the aircraft to the gross weight of the aircraft.
1. Normal category airplanes are limited to +3.8 and –1.52 Gs.
2. Utility aircraft are limited to +4.4 and –1.76 Gs.
3. Aerobatic aircraft are limited to +6.0 and –3.0 Gs.
4. When baggage or other areas of the plane are placarded for weight, they are placarded for gross weight. The airplane is designed to accommodate the specified Gs (+3.8, +4.4, +6.0) given the weight placarded.
5. A “stall speed vs. load factor” graph relates these variables to the degree of bank angle for a particular airplane, as illustrated in Figure 4 below.
a. Determine the load factor (or G units) for any bank angle by finding the bank angle on the horizontal axis, moving vertically up to the intersection with the load factor curve, and then proceeding horizontally to the right of the graph to find the number of G units on the vertical load factor scale.
b. To determine the increase in stall speed for any load factor, begin with the load factor on the far right vertical scale and move horizontally to intersect the load factor curve. From that point of intersection, move up vertically to the intersection with the stall speed increase curve. From that point, move horizontally to the left to the vertical axis to determine the percentage increase in stall speed.

Figure 4. Stall Speed vs. Load Factor.